Honors & Awards

  • The Alavi-Mandell Award (I) - 2022, Society of Nuclear Medicine and Molecular Imaging (SNMMI) (2022)
  • The Alavi-Mandell Award (II) - 2022, Society of Nuclear Medicine and Molecular Imaging (SNMMI) (2022)
  • PCF - Young Investigator Award - 2021, Prostate Cancer Foundation (PCF) (2021)
  • Sanjiv Sam Gambhir—Philips Fellowship, Stanford Medicine - PHIND (2021)
  • The Alavi-Mandell Award - 2020, Society of Nuclear Medicine and Molecular Imaging (SNMMI) (2020)
  • Scholarship for Training Course on Experimental Modeling of Human Cancer, The Jackson Laboratory (2019)
  • RSNA Student Travel Award - 2018, Radiological Society of North America (RSNA) (2018)
  • AACR Scholar-in-Training Award 2018, American Association for Cancer Research (AACR) (2018)
  • Graduate School Research Grant Competition Award, University of Wisconsin-Madison Graduate School (2018)

Professional Education

  • Doctor of Philosophy, University of Wisconsin Madison (2020)
  • Bachelor of Technology, Unlisted School (2010)
  • Master of Science, University of Wisconsin Madison (2014)
  • Doctor of Philosophy (Ph.D.), University of Wisconsin-Madison, Clinical Investigation (2020)
  • Master of Science (MS), University of Wisconsin-Madison, Biotechnology (2014)
  • Bachelor of Technology (B.Tech), Uttar Pradesh Technical University, Biotechnology (2010)

Stanford Advisors

Current Research and Scholarly Interests

I work on imaging-guided therapy using PET and MR imaging approaches. My academic training and background is in molecular imaging. During my doctoral training, I developed and validated a PET imaging approach for evaluating endocrine therapy responses in advanced breast cancer. My current research focuses on imaging tumor immune markers and responses to cancer immunotherapy. The goal is to develop new imaging toolboxes to monitor and guide treatment. Specifically, I employ antibodies, nanoparticles, and reporter genes for imaging and combinations of therapies to modulate and restore the body's suppressed immune functions against cancer cells. This is being done in collaboration with teams of researchers in early clinical development and teams in clinical practice.

Lab Affiliations

All Publications

  • PET Imaging of Estrogen Receptors Using 18F-Based Radioligands. Methods in molecular biology (Clifton, N.J.) Kumar, M., Salem, K., Jeffery, J. J., Fowler, A. M. 1800; 2418: 129-151


    In vivo molecular imaging of estrogen receptor alpha (ER) can be performed via positron emission tomography (PET) using ER-specific radioligands, such as 16alpha-[18F]fluoro-17beta-estradiol (18F-FES). 18F-FES is a radiopharmaceutical recently approved by the United States Food and Drug Administration for use with PET imaging to detect ER+ lesions in patients with recurrent or metastatic breast cancer as an adjunct to biopsy. 18F-FES PET imaging has been used in clinical studies and preclinical research to assess whole-body ER protein expression and ligand binding function across multiple metastatic sites, to demonstrate inter-tumoral and temporal heterogeneity of ER expression, to quantify the pharmacodynamic effects of ER antagonist treatment, and to predict endocrine therapy response. 18F-FES PET has also been studied for imaging ER in endometrial and ovarian cancer. This chapter details the experimental protocol for 18F-FES PET imaging of ER in preclinical tumor xenograft models. Consistent adherence to key methodologic details will facilitate obtaining meaningful and reproducible 18F-FES PET preclinical imaging results, which could yield additional insight for clinical trials regarding imaging biomarkers and oncologic therapy.

    View details for DOI 10.1007/978-1-0716-1920-9_9

    View details for PubMedID 35119664

  • Recent Advances in Imaging Steroid Hormone Receptors in Breast Cancer JOURNAL OF NUCLEAR MEDICINE Kumar, M., Salem, K., Tevaarwerk, A. J., Strigel, R. M., Fowler, A. M. 2020; 61 (2): 172–76


    Estrogen receptor (ER) and progesterone receptor (PR) are important prognostic and predictive biomarkers in breast cancer. PET using ER- and PR-specific radioligands enables a whole-body, noninvasive assessment of receptor expression. Recent investigations of ER imaging with 18F-fluoroestradiol have focused on diagnosing ER-positive metastatic disease, optimizing ER-targeted drug dosage, and predicting endocrine therapy benefit. Studies of PR imaging with 18F-fluorofuranyl norprogesterone have investigated how imaging changes in PR expression as a downstream target of ER activation may reflect an early response to ER-targeted therapy. This focused review highlights recent achievements in preclinical and clinical imaging of ER and PR in breast cancer.

    View details for DOI 10.2967/jnumed.119.228858

    View details for Web of Science ID 000512119600008

    View details for PubMedID 31732674

  • Longitudinal molecular imaging of progesterone receptor reveals early differential response to endocrine therapy in breast cancer with an activating ESR1 mutation. Journal of nuclear medicine : official publication, Society of Nuclear Medicine Kumar, M. n., Salem, K. n., Jeffery, J. J., Yan, Y. n., Mahajan, A. M., Fowler, A. M. 2020


    Activating mutations in the estrogen receptor (ER) alpha gene (ESR1) result in constitutive transcriptional activity in the absence of estrogen and is associated with endocrine resistance in metastatic ER+ breast cancer. It is not known how activating ESR1 mutations may alter the predictive values of molecular imaging agents for endocrine therapy response. This study investigated the effect of an activating ESR1 mutation on pre-treatment 18F-fluoroestradiol (18F-FES) uptake and early assessment of endocrine therapy response using 18F-FDG and 18F-fluorofuranylnorprogesterone (18F-FFNP) PET/CT imaging of tumor glucose metabolism and progesterone receptor (PR) expression, respectively. Methods: ER+PR+ T47D breast cancer cells expressing wild-type (WT)-ER or an activating ESR1 mutation, Y537S-ER, were used to generate tumor xenografts in ovariectomized female immunodeficient mice supplemented with 17β-estradiol. Tumor growth curves were determined in the presence or absence of estrogen and for ethanol vehicle control or fulvestrant treatment, a selective ER degrader. Pre-treatment 18F-FES uptake was compared between Y537S-ER and WT-ER tumors. Longitudinal PET/CT imaging with 18F-FFNP and 18F-FDG was performed before and 7 to 9 days after starting endocrine therapy with fulvestrant. Radiopharmaceutical uptake in Y537S-ER and WT-ER tumors were compared between baseline and follow-up scans. Statistical significance was determined using paired t-tests for longitudinal imaging and two-way ANOVA for 18F-FFNP tissue biodistribution assay. Results: Y537S-ER xenografts showed estrogen-independent growth, while WT-ER tumors grew only with estrogen. Fulvestrant treatment for 28 days significantly reduced tumor volumes for WT-ER, but only stabilized volumes for Y537S-ER. Baseline 18F-FES uptake was not significantly different between WT-ER and Y537S-ER tumors. Fulvestrant treatment induced a similar early metabolic response for both WT-ER and Y537S-ER tumors. 18F-FFNP uptake in WT-ER tumors was significantly reduced after 7 days of fulvestrant treatment; however, this reduction did not occur in Y537S-ER tumors which showed no significant change between baseline and follow-up PET/CT. Conclusion: Molecular imaging of PR expression dynamics could be a non-invasive approach for early identification of reduced effectiveness of endocrine therapy resulting from activating ESR1 mutations.

    View details for DOI 10.2967/jnumed.120.249508

    View details for PubMedID 32859700

  • F-18-Fluoroestradiol PET Imaging of Activating Estrogen Receptor-alpha Mutations in Breast Cancer JOURNAL OF NUCLEAR MEDICINE Kumar, M., Salem, K., Michel, C., Jeffery, J. J., Yan, Y., Fowler, A. M. 2019; 60 (9): 1247–52


    The purpose of this study was to determine the effect of estrogen receptor-α gene (ESR1) mutations at the tyrosine (Y) 537 amino acid residue within the ligand binding domain on 18F-fluoroestradiol (18F-FES) binding and in vivo tumor uptake compared with wild-type (WT)-estrogen receptor α (ER). Methods: ER-negative MDA-MB-231 breast cancer cells were used to generate stable cell lines that express WT-ER, Y537S, or Y537C mutant ER. Receptor expression and localization were confirmed by Western blot and immunofluorescence, respectively. ER transcriptional function was measured using an estrogen response element-luciferase reporter gene assay and quantitative polymerase chain reaction analysis of ER-regulated endogenous target genes. Saturation binding and competition assays were performed to determine equilibrium dissociation constant (Kd) and half maximal inhibitory concentration (IC50) values. 18F-FES uptake was measured in tumor xenografts grown in female athymic nude mice by small-animal PET/CT imaging and tissue biodistribution using 5.55 MBq (150 μCi) of 18F-FES. A 10-fold-lower injected dose of 0.555 MBq (15 μCi) of 18F-FES was also used for tissue biodistribution. Statistical significance was determined using ANOVA. Results: Y537S and Y537C mutations resulted in increased ER transcriptional activity in the absence of estrogen compared with WT-ER (11.48 ± 2.42 fold; P = 0.0002, and 5.89 ± 0.94 fold; P = 0.04, respectively). Constitutive ER activation of two target genes (PGR and TFF1) in the absence of estrogen was also observed in Y537S- and Y537C-ER cells compared with WT-ER. Kd values for 18F-FES were 0.98 ± 0.54 nM for Y537S-ER (P = 0.27) and 0.24 ± 0.03 nM for Y537C-ER (P = 0.95) compared with 0.07 ± 0.03 nM for WT-ER. IC50 values were 0.22 ± 0.09 nM for Y537S-ER (P = 0.97), 0.18 ± 0.09 nM for Y537C-ER (P = 0.99), and 0.19 ± 0.11 nM for WT-ER. Tumor xenografts expressing Y537S-ER (mean percentage injected dose per gram, 1.45 ± 0.06; P = 0.77) and Y537C-ER (2.09 ± 0.20; P = 0.21) had similar 18F-FES uptake compared with WT-ER (1.68 ± 0.12). Comparable 18F-FES uptake between Y537S-, Y537C-, and WT-ER xenografts was also observed using a 10-fold-lower injected dose with the tissue biodistribution assay. Conclusion: Since tumoral uptake of 18F-FES is not significantly impacted by Y537S-ER or Y537C-ER mutations, the potential diagnostic utility of 18F-FES PET imaging is expected to be equally valid for patients with or without these activating ESR1 mutations.

    View details for DOI 10.2967/jnumed.118.224667

    View details for Web of Science ID 000484372100017

    View details for PubMedID 30850489

    View details for PubMedCentralID PMC6735277

  • F-18-16 alpha-17 beta-Fluoroestradiol Binding Specificity in Estrogen Receptor-Positive Breast Cancer RADIOLOGY Salem, K., Kumar, M., Powers, G. L., Jeffery, J. J., Yan, Y., Mahajan, A. M., Fowler, A. M. 2018; 286 (3): 868–76


    Purpose To determine the binding specificity of 18F-16α-17β-fluoroestradiol (FES) in estrogen receptor (ER) α-positive breast cancer cells and tumor xenografts. Materials and Methods Protocols were approved by the office of biologic safety and institutional animal care and use committee. By using ER-negative MDA-MB-231 breast cancer cells, clonal lines were created that expressed either wild-type (WT; 231 WT ER) or G521R mutant ERα (231 G521R ER), which is defective in estradiol binding. ERα protein levels, subcellular localization, and transcriptional function were confirmed. FES binding was measured by using an in vitro cell uptake assay. In vivo FES uptake was measured in tumor xenografts by using small-animal positron emission tomographic/computed tomographic imaging of 24 mice (17 WT ER tumors, nine mutant G521R ER tumors, eight MDA-MB-231 tumors, and four MCF-7 ER-positive tumors). Statistical significance was determined by using Mann-Whitney (Wilcoxon rank sum) test. Results ERα transcriptional function was abolished in the mutated 231 G521R ER cells despite appropriate receptor protein expression and nuclear localization. In vitro FES binding in the 231 G521R ER cells was reduced to that observed in the parental cells. Similarly, there was no significant FES uptake in the 231 G521R ER xenografts (percent injected dose [ID] per gram, 0.49 ± 0.042), which was similar to the negative control MDA-MB-231 xenografts (percent ID per gram, 0.42 ± 0.051; P = .20) and nonspecific muscle uptake (percent ID per gram, 0.41 ± 0.0095; P = .06). Conclusion This study showed that FES retention in ER-positive breast cancer is strictly dependent on an intact receptor ligand-binding pocket and that FES binds to ERα with high specificity. These results support the utility of FES imaging for assessing tumor heterogeneity by localizing immunohistochemically ER-positive metastases that lack receptor-binding functionality. © RSNA, 2017 Online supplemental material is available for this article.

    View details for DOI 10.1148/radiol.2017162956

    View details for Web of Science ID 000425583200015

    View details for PubMedID 28956736

    View details for PubMedCentralID PMC5882239

  • Attenuation correction and truncation completion for breast PET/MR imaging using deep learning. Physics in medicine and biology Li, X., Johnson, J., Strigel, R. M., Bancroft, L. C., Hurley, S. A., Estakhraji, I. Z., Kumar, M., Fowler, A. M., McMillan, A. B. 2024


    OBJECTIVE: Simultaneous PET/MR scanners combine the high sensitivity of MR imaging with the functional imaging of PET. However, attenuation correction of breast PET/MR imaging is technically challenging. The purpose of this study is to establish a robust attenuation correction algorithm for breast PET/MR images that relies on deep learning (DL) to recreate the missing portions of the patient's anatomy (truncation completion), as well as to provide bone information for attenuation correction from only the PET data.APPROACH: Data acquired from 23 female subjects with invasive breast cancer scanned with 18F-fluorodeoxyglucose PET/CT and PET/MR localized to the breast region were used for this study. Three DL models, U-Net with mean absolute error loss (DLMAE) model, U-Net with mean squared error loss (DLMSE) model, and U-Net with perceptual loss (DLPerceptual) model, were trained to predict synthetic CT images (sCT) for PET attenuation correction (AC) given non-attenuation corrected (NAC) PETPET/MRimages as inputs. The DL and Dixon-based sCT reconstructed PET images were compared against those reconstructed from CT images by calculating the percent error of the standardized uptake value (SUV) and conducting Wilcoxon signed rank statistical tests.MAIN RESULTS: sCT images from the DLMAEmodel, the DLMSEmodel, and the DLPerceptualmodel were similar in mean absolute error (MAE), peak-signal-to-noise ratio (PSNR), and normalized cross-correlation (NCC). No significant difference in SUV was found between the PET images reconstructed using the DLMSEand DLPerceptualsCTs compared to the reference CT for AC in all tissue regions. All DL methods performed better than the Dixon-based method according to SUV analysis.SIGNIFICANCE: A 3D U-Net with MSE or perceptual loss model can be implemented into a reconstruction workflow, and the derived sCT images allow successful truncation completion and attenuation correction for breast PET/MR images.

    View details for DOI 10.1088/1361-6560/ad2126

    View details for PubMedID 38252969

  • PET/CT in the Evaluation of CAR-T Cell Immunotherapy in Hematological Malignancies Molecular Imaging Singh, S. B., Bhandari, S., Siwakoti, S., Singh, R., Bhusal, S., Sharma, K., Bhandari, S., Khanal, K. 2024; 23: 15353508241257924
  • Spatial mapping of cellular senescence: emerging challenges and opportunities. Nature aging Gurkar, A. U., Gerencser, A. A., Mora, A. L., Nelson, A. C., Zhang, A. R., Lagnado, A. B., Enninful, A., Benz, C., Furman, D., Beaulieu, D., Jurk, D., Thompson, E. L., Wu, F., Rodriguez, F., Barthel, G., Chen, H., Phatnani, H., Heckenbach, I., Chuang, J. H., Horrell, J., Petrescu, J., Alder, J. K., Lee, J. H., Niedernhofer, L. J., Kumar, M., Konigshoff, M., Bueno, M., Sokka, M., Scheibye-Knudsen, M., Neretti, N., Eickelberg, O., Adams, P. D., Hu, Q., Zhu, Q., Porritt, R. A., Dong, R., Peters, S., Victorelli, S., Pengo, T., Khaliullin, T., Suryadevara, V., Fu, X., Bar-Joseph, Z., Ji, Z., Passos, J. F. 2023


    Cellular senescence is a well-established driver of aging and age-related diseases. There are many challenges to mapping senescent cells in tissues such as the absence of specific markers and their relatively low abundance and vast heterogeneity. Single-cell technologies have allowed unprecedented characterization of senescence; however, many methodologies fail to provide spatial insights. The spatial component is essential, as senescent cells communicate with neighboring cells, impacting their function and the composition of extracellular space. The Cellular Senescence Network (SenNet), a National Institutes of Health (NIH) Common Fund initiative, aims to map senescent cells across the lifespan of humans and mice. Here, we provide a comprehensive review of the existing and emerging methodologies for spatial imaging and their application toward mapping senescent cells. Moreover, we discuss the limitations and challenges inherent to each technology. We argue that the development of spatially resolved methods is essential toward the goal of attaining an atlas of senescent cells.

    View details for DOI 10.1038/s43587-023-00446-6

    View details for PubMedID 37400722

  • Surface-Engineered Extracellular Vesicles in Cancer Immunotherapy. Cancers Johnson, V., Vasu, S., Kumar, U. S., Kumar, M. 2023; 15 (10)


    Extracellular vesicles (EVs) are lipid bilayer-enclosed bodies secreted by all cell types. EVs carry bioactive materials, such as proteins, lipids, metabolites, and nucleic acids, to communicate and elicit functional alterations and phenotypic changes in the counterpart stromal cells. In cancer, cells secrete EVs to shape a tumor-promoting niche. Tumor-secreted EVs mediate communications with immune cells that determine the fate of anti-tumor therapeutic effectiveness. Surface engineering of EVs has emerged as a promising tool for the modulation of tumor microenvironments for cancer immunotherapy. Modification of EVs' surface with various molecules, such as antibodies, peptides, and proteins, can enhance their targeting specificity, immunogenicity, biodistribution, and pharmacokinetics. The diverse approaches sought for engineering EV surfaces can be categorized as physical, chemical, and genetic engineering strategies. The choice of method depends on the specific application and desired outcome. Each has its advantages and disadvantages. This review lends a bird's-eye view of the recent progress in these approaches with respect to their rational implications in the immunomodulation of tumor microenvironments (TME) from pro-tumorigenic to anti-tumorigenic ones. The strategies for modulating TME using targeted EVs, their advantages, current limitations, and future directions are discussed.

    View details for DOI 10.3390/cancers15102838

    View details for PubMedID 37345176

    View details for PubMedCentralID PMC10216164

  • Surface-Engineered Extracellular Vesicles in Cancer Immunotherapy CANCERS Johnson, V., Vasu, S., Kumar, U. S., Kumar, M. 2023; 15 (10)
  • NIH SenNet Consortium to map senescent cells throughout the human lifespan to understand physiological health NATURE AGING Lee, P. J., Benz, C. C., Blood, P., Boerner, K., Campisi, J., Chen, F., Daldrup-Link, H., De Jager, P., Ding, L., Duncan, F. E., Eickelberg, O., Fan, R., Finkel, T., Furman, D., Garovic, V., Gehlenborg, N., Glass, C., Heckenbach, I., Joseph, Z., Katiyar, P., Kim, S., Koenigshoff, M., Kuchel, G. A., Lee, H., Lee, J., Ma, J., Ma, Q., Melov, S., Metis, K., Mora, A. L., Musi, N., Neretti, N., Passos, J. F., Rahman, I., Rivera-Mulia, J., Robson, P., Rojas, M., Roy, A. L., Scheibye-Knudsen, M., Schilling, B., Shi, P., Silverstein, J. C., Suryadevara, V., Xie, J., Wang, J., Wong, A., Niedernhofer, L. J., Wang, S., Anvari, H., Balough, J., Benz, C., Bons, J., Brenerman, B., Evans, W., Gerencser, A., Gregory, H., Hansen, M., Justice, J., Kapahi, P., Murad, N., O'Broin, A., Pavone, M., Powell, M., Scott, G., Shanes, E., Shankaran, M., Verdin, E., Winer, D., Wu, F., Adams, A., Blood, P. D., Bueckle, A., Cao-Berg, I., Chen, H., Davis, M., Filus, S., Hao, Y., Hartman, A., Hasanaj, E., Helfer, J., Herr, B., Bar Joseph, Z., Molla, G., Mou, G., Puerto, J., Quardokus, E. M., Ropelewski, A. J., Ruffalo, M., Satija, R., Schwenk, M., Scibek, R., Shirey, W., Sibilla, M., Welling, J., Yuan, Z., Bonneau, R., Christiano, A., Izar, B., Menon, V., Owens, D. M., Phatnani, H., Smith, C., Suh, Y., Teich, A. F., Bekker, V., Chan, C., Coutavas, E., Hartwig, M. G., Ji, Z., Nixon, A. B., Dou, Z., Rajagopal, J., Slavov, N., Holmes, D., Jurk, D., Kirkland, J. L., Lagnado, A., Tchkonia, T., Abraham, K., Dibattista, A., Fridell, Y., Howcroft, T., Jhappan, C., Montes, V., Prabhudas, M., Resat, H., Taylor, V., Kumar, M., Cigarroa, F., Cohn, R., Cortes, T. M., Courtois, E., Chuang, J., Dave, M., Domanskyi, S., Enninga, E., Eryilmaz, G., Espinoza, S. E., Gelfond, J., Kirkland, J., Kuo, C., Lehman, J. S., Aguayo-Mazzucato, C., Meves, A., Rani, M., Sanders, S., Thibodeau, A., Tullius, S. G., Ucar, D., White, B., Wu, Q., Xu, M., Yamaguchi, S., Assarzadegan, N., Cho, C., Hwang, I., Hwang, Y., Xi, J., Adeyi, O. A., Aliferis, C. F., Bartolomucci, A., Dong, X., DuFresne-To, M. J., Ikramuddin, S., Johnson, S. G., Nelson, A. C., Revelo, X. S., Trevilla-Garcia, C., Sedivy, J. M., Thompson, E. L., Robbins, P. D., Wang, J., Aird, K. M., Alder, J. K., Beaulieu, D., Bueno, M., Calyeca, J., Chamucero-Millaris, J. A., Chan, S. Y., Chung, D., Corbett, A., Gorbunova, V., Gowdy, K. M., Gurkar, A., Horowitz, J. C., Hu, Q., Kaur, G., Khaliullin, T. O., Lafyatis, R., Lanna, S., Li, D., Ma, A., Morris, A., Muthumalage, T. M., Peters, V., Pryhuber, G. S., Reader, B. F., Rosas, L., Sembrat, J. C., Shaikh, S., Shi, H., Stacey, S. D., St Croix, C., Wang, C., Wang, Q., Watts, A., Gu, L., Lin, Y., Rabinovitch, P. S., Sweetwyne, M. T., Artyomov, M. N., Ballentine, S. J., Chheda, M. G., Davies, S. R., DiPersio, J. F., Fields, R. C., Fitzpatrick, J. J., Fulton, R. S., Imai, S., Jain, S., Ju, T., Kushnir, V. M., Link, D. C., Ben Major, M., Oh, S. T., Rapp, D., Rettig, M. P., Stewart, S. A., Veis, D. J., Vij, K. R., Wendl, M. C., Wyczalkowski, M. A., Craft, J. E., Enninful, A., Farzad, N., Gershkovich, P., Halene, S., Kluger, Y., VanOudenhove, J., Xu, M., Yang, J., Yang, M., SenNet Consortium 2022; 2 (12): 1090-1100
  • Gadolinium-based contrast agent attenuation does not impact PET quantification in simultaneous dynamic contrast enhanced breast PET/MR. Medical physics Allen, T. J., Henze Bancroft, L. C., Kumar, M., Bradshaw, T. J., Strigel, R. M., McMillan, A. B., Fowler, A. M. 2022


    Simultaneous PET/MR imaging involves injection of a radiopharmaceutical and often also includes administration of a gadolinium-based contrast agent (GBCA). Phantom model studies indicate that attenuation of annihilation photons by GBCAs does not bias quantification metrics of PET radiopharmaceutical uptake. However, a direct comparison of attenuation-corrected PET values before and after administration of GBCA has not been performed in patients imaged with simultaneous dynamic PET/MR. The purpose of this study was to investigate the attenuating effect of GBCAs on standardized uptake value (SUV) quantification of 18 F-fluorodeoxyglucose (FDG) uptake in invasive breast cancer and normal tissues using simultaneous PET/MR.The study included 13 women with newly diagnosed invasive breast cancer imaged using simultaneous dedicated prone breast PET/MR with FDG. PET data collection and two-point Dixon-based MR attenuation correction sequences began simultaneously before the administration of GBCA to avoid a potential impact of GBCA on the attenuation correction map. A standard clinical dose of GBCA was intravenously administered for the dynamic contrast enhanced MR sequences obtained during the simultaneous PET data acquisition. PET data were dynamically reconstructed into 60 frames of 30 s each. Three timing windows were chosen consisting of a single frame (30 s), two frames (60 s), or four frames (120 s) immediately before and after contrast administration. SUVmax and SUVmean of the biopsy-proven breast malignancy, fibroglandular tissue of the contralateral normal breast, descending aorta, and liver were calculated prior to and following GBCA administration. Percent change in the SUV metrics were calculated to test for a statistically significant, non-zero percent change using Wilcoxon signed-rank tests.No statistical change in SUVmax or SUVmean was found for the breast malignancies or normal anatomical regions during the timing windows before and after GBCA administration.GBCAs do not significantly impact the results of PET quantification by means of additional attenuation. However, GBCAs may still affect quantification by affecting MR acquisitions used for MR-based attenuation correction which this study did not address. Corrections to account for attenuation due to clinical concentrations of GBCAs are not necessary in simultaneous PET/MR examinations when MR-based attenuation correction sequences are performed prior to GBCA administration.

    View details for DOI 10.1002/mp.15781

    View details for PubMedID 35621727

  • SU086, an inhibitor of HSP90, impairs glycolysis and represents a treatment strategy for advanced prostate cancer. Cell reports. Medicine Rice, M. A., Kumar, V., Tailor, D., Garcia-Marques, F. J., Hsu, E., Liu, S., Bermudez, A., Kanchustambham, V., Shankar, V., Inde, Z., Alabi, B. R., Muruganantham, A., Shen, M., Pandrala, M., Nolley, R., Aslan, M., Ghoochani, A., Agarwal, A., Buckup, M., Kumar, M., Going, C. C., Peehl, D. M., Dixon, S. J., Zare, R. N., Brooks, J. D., Pitteri, S. J., Malhotra, S. V., Stoyanova, T. 2022; 3 (2): 100502


    Among men, prostate cancer is the second leading cause of cancer-associated mortality, with advanced disease remaining a major clinical challenge. We describe a small molecule, SU086, as a therapeutic strategy for advanced prostate cancer. We demonstrate that SU086 inhibits the growth of prostate cancer cells invitro, cell-line and patient-derived xenografts invivo, and exvivo prostate cancer patient specimens. Furthermore, SU086 in combination with standard of care second-generation anti-androgen therapies displays increased impairment of prostate cancer cell and tumor growth invitro and invivo. Cellular thermal shift assay reveals that SU086 binds to heat shock protein 90 (HSP90) and leads to a decrease in HSP90 levels. Proteomic profiling demonstrates that SU086 binds to and decreases HSP90. Metabolomic profiling reveals that SU086 leads to perturbation of glycolysis. Our study identifies SU086 as a treatment for advanced prostate cancer as a single agent or when combined with second-generation anti-androgens.

    View details for DOI 10.1016/j.xcrm.2021.100502

    View details for PubMedID 35243415

  • Measuring Glucose Uptake in Primary Invasive Breast Cancer Using Simultaneous Time-of-Flight Breast PET/MRI: A Method Comparison Study with Prone PET/CT. Radiology. Imaging cancer Fowler, A. M., Kumar, M., Bancroft, L. H., Salem, K., Johnson, J. M., Karow, J., Perlman, S. B., Bradshaw, T. J., Hurley, S. A., McMillan, A. B., Strigel, R. M. 2021; 3 (1): e200091


    To compare the measurement of glucose uptake in primary invasive breast cancer using simultaneous, time-of-flight breast PET/MRI with prone time-of-flight PET/CT.In this prospective study, women with biopsy-proven invasive breast cancer undergoing preoperative breast MRI from 2016 to 2018 were eligible. Participants who had fasted underwent prone PET/CT of the breasts approximately 60 minutes after injection of 370 MBq (10 mCi) fluorine 18 fluorodeoxyglucose (18F-FDG) followed by prone PET/MRI using standard clinical breast MRI sequences performed simultaneously with PET acquisition. Volumes of interest were drawn for tumors and contralateral normal breast fibroglandular tissue to calculate standardized uptake values (SUVs). Spearman correlation, Wilcoxon signed ranked test, Mann-Whitney test, and Bland-Altman analyses were performed.Twenty-three women (mean age, 50 years; range, 33-70 years) were included. Correlation between tumor uptake values measured with PET/MRI and PET/CT was strong (r s = 0.95-0.98). No difference existed between modalities for tumor maximum SUV (SUVmax) normalized to normal breast tissue SUVmean (normSUVmax) (P = .58). The least amount of measurement bias was observed with normSUVmax, +3.86% (95% limits of agreement: -28.92, +36.64).These results demonstrate measurement agreement between PET/CT, the current reference standard for tumor glucose uptake quantification, and simultaneous time-of-flight breast 18F-FDG PET/MRI.Keywords: Breast, Comparative Studies, PET/CT, PET/MR Supplemental material is available for this article. © RSNA, 2021See also the commentary by Mankoff and Surti in this issue.

    View details for DOI 10.1148/rycan.2021200091

    View details for PubMedID 33575660

    View details for PubMedCentralID PMC7850238

  • MCM2-7 complex is a novel druggable target for neuroendocrine prostate cancer. Scientific reports Hsu, E. C., Shen, M., Aslan, M., Liu, S., Kumar, M., Garcia-Marques, F., Nguyen, H. M., Nolley, R., Pitteri, S. J., Corey, E., Brooks, J. D., Stoyanova, T. 2021; 11 (1): 13305


    Neuroendocrine prostate cancer (NEPC) is a lethal subtype of prostate cancer that rarely develops de novo in primary tumors and is commonly acquired during the development of treatment resistance. NEPC is characterized by gain of neuroendocrine markers and loss of androgen receptor (AR), making it resistant to current therapeutic strategies targeting the AR signaling axis. Here, we report that MCM2, MCM3, MCM4, and MCM6 (MCM2/3/4/6) are elevated in human NEPC and high levels of MCM2/3/4/6 are associated with liver metastasis and poor survival in prostate cancer patients. MCM2/3/4/6 are four out of six proteins that form a core DNA helicase (MCM2-7) responsible for unwinding DNA forks during DNA replication. Inhibition of MCM2-7 by treatment with ciprofloxacin inhibits NEPC cell proliferation and migration in vitro, significantly delays NEPC tumor xenograft growth, and partially reverses the neuroendocrine phenotype in vivo. Our study reveals the clinical relevance of MCM2/3/4/6 proteins in NEPC and suggests that inhibition of MCM2-7 may represent a new therapeutic strategy for NEPC.

    View details for DOI 10.1038/s41598-021-92552-x

    View details for PubMedID 34172788

  • Progesterone Receptor Gene Variants in Metastatic Estrogen Receptor Positive Breast Cancer HORMONES & CANCER Fowler, A. M., Salem, K., DeGrave, M., Ong, I. M., Rassman, S., Powers, G. L., Kumar, M., Michel, C. J., Mahajan, A. M. 2020; 11 (2): 63–75


    Tumor mutations in the gene encoding estrogen receptor alpha (ESR1) have been identified in metastatic breast cancer patients with endocrine therapy resistance. However, relatively little is known about the occurrence of mutations in the progesterone receptor (PGR) gene in this population. The study objective was to determine the frequency and prognostic significance of tumor PGR mutations for patients with estrogen receptor (ER)-positive metastatic breast cancer. Thirty-five women with metastatic or locally recurrent ER+ breast cancer were included in this IRB-approved, retrospective study. Targeted next-generation sequencing of the PGR gene was performed on isolated tumor DNA. Associations between mutation status and clinicopathologic factors were analyzed as well as overall survival (OS) from time of metastatic diagnosis. The effect of the PGR variant Y890C (c.2669A>G) identified in this cohort on PR transactivation function was tested using ER-PR- (MDA-MB-231), ER+PR+ (T47D), and ER+PR- (T47D PR KO) breast cancer cell lines. There were 71 occurrences of protein-coding PGR variants in 67% (24/36; 95% CI 49-81%) of lesions. Of the 49 unique variants, 14 are single nucleotide polymorphisms (SNPs). Excluding SNPs, the median OS of patients with PGR variants was 32 months compared to 79 months with wild-type PGR (p = 0.42). The most frequently occurring (4/36 lesions) non-SNP variant was Y890C. Cells expressing Y890C had reduced progestin-stimulated PR transactivation compared to cells expressing wild-type PR. PGR variants occur frequently in ER+ metastatic breast cancer. Although some variants are SNPs, others are predicted to be functionally deleterious as demonstrated with Y890C PR.

    View details for DOI 10.1007/s12672-020-00377-3

    View details for Web of Science ID 000507348600001

    View details for PubMedID 31942683

    View details for PubMedCentralID PMC7152560

  • Sensitivity and Isoform Specificity of F-18-Fluorofuranylnorprogesterone for Measuring Progesterone Receptor Protein Response to Estradiol Challenge in Breast Cancer JOURNAL OF NUCLEAR MEDICINE Salem, K., Kumar, M., Yan, Y., Jeffery, J. J., Kloepping, K. C., Michel, C. J., Powers, G. L., Mahajan, A. M., Fowler, A. M. 2019; 60 (2): 220–26


    The purpose of this study was to evaluate the ability of 21-18F-fluoro-16α,17α-[(R)-(1'-α-furylmethylidene)dioxy]-19-norpregn-4-ene-3,20-dione (18F-FFNP) to measure alterations in progesterone receptor (PR) protein level and isoform expression in response to estradiol challenge. Methods: T47D human breast cancer cells and female mice-bearing T47D tumor xenografts were treated with 17β-estradiol (E2) to increase PR expression. 18F-FFNP uptake was measured using cell uptake and tissue biodistribution assays. MDA-MB-231 breast cancer clonal cell lines were generated that express the A or B isoforms of human PR. PR protein levels, transcriptional function, and subcellular localization were determined. In vitro 18F-FFNP binding was measured via saturation and competitive binding curves. In vivo 18F-FFNP uptake was measured using tumor xenografts and positron emission tomography. Statistical significance was determined using analysis of variance and t-tests. Results: After 48 and 72 h of E2, 18F-FFNP uptake in T47D cells was maximally increased compared to both vehicle and 24 h E2 treatment (p<0.0001 vs ethanol; P = 0.02 and P = 0.0002 vs 24 h for 48 and 72 h, respectively). T47D tumor xenografts in mice treated with 72 h E2 had maximal 18F-FFNP uptake compared to ethanol-treated mice (11.3±1.4 vs 5.2±0.81 %ID/g; P = 0.002). Corresponding tumor-to-muscle uptake ratios were 4.1±0.6, 3.9±0.5, and 2.3±0.4 for 48 h E2, 72 h E2, and ethanol-treated mice, respectively. There was no significant preferential 18F-FFNP binding or uptake by PR-A versus PR-B in the PR isoform-specific cell lines and tumor xenografts. Conclusion:18F-FFNP is capable of measuring estrogen-induced shifts in total PR expression in human breast cancer cells and tumor xenografts with equivalent isoform binding.

    View details for DOI 10.2967/jnumed.118.211516

    View details for Web of Science ID 000457479800020

    View details for PubMedID 30030339

  • Determination of binding affinity of molecular imaging agents for steroid hormone receptors in breast cancer. American journal of nuclear medicine and molecular imaging Salem, K., Kumar, M., Kloepping, K. C., Michel, C. J., Yan, Y., Fowler, A. M. 2018; 8 (2): 119-126


    16α-[18F]Fluoro-17β-estradiol ([18F]FES) and 21-[18F]-Fluoro-16α,17α-[(R)-(1'-α-furylmethylidene)dioxyl]-19-norpregn-4-ene-3,20-dione ([18F]FFNP) are being investigated as imaging biomarkers for breast cancer patients. Quantitative positron emission tomography (PET) reflects both total receptor content and binding affinity. To study factors that may alter radiopharmaceutical binding and impact PET accuracy, assays that can separate receptor amount from binding affinity are needed. The study purpose was to quantify the binding parameters of [18F]FES and [18F]FFNP in breast cancer. Estrogen receptor-alpha (ER) and progesterone receptor (PR) positive breast cancer cell lines (MCF-7 and T47D) were used to measure [18F]FES and [18F]FFNP binding parameters via saturation and competitive binding curves. The equilibrium dissociation constant (Kd) and total receptor density (Bmax) were determined using nonlinear regression of the saturation binding curves. Half-maximal inhibitory concentration (IC50) was determined using nonlinear regression of the competitive binding curves. Linear correlation between increasing cell number and tracer uptake was observed for both [18F]FES and [18F]FFNP (R2=0.99 and 0.91, respectively). Using [18F]FES, the Kd for ER in MCF-7 cells was 0.13±0.02 nM with a Bmax of 1901±89.3 fmol/mg protein and IC50 of 0.085 nM (95% CI: 0.069-0.104 nM). Using [18F]FFNP, the Kd for PR in T47D cells was 0.41±0.05 nM with a Bmax of 1984±75.6 fmol/mg protein and IC50 of 2.6 nM (95% CI: 2.0-3.4 nM). The ligand binding function of ER and PR can be quantified using [18F]FES and [18F]FFNP and are comparable to previous studies using tritiated radioligands. [18F]FES and [18F]FFNP can be used in cell-based assays to quantify receptor-radioligand binding affinity, which cannot be obtained from a single PET examination.

    View details for PubMedID 29755845

    View details for PubMedCentralID PMC5944827

  • Dendrimer-stabilized smart-nanoparticle (DSSN) platform for targeted delivery of hydrophobic antitumor therapeutics PHARMACEUTICAL RESEARCH Tekade, R. K., Tekade, M., Kumar, M., Chauhan, A. S. 2015; 32 (3): 910–28


    To formulate dendrimer-stabilized smart-nanoparticle (DSSN; pD-ANP-f) for the targeted delivery of the highly hydrophobic anticancer drug, Paclitaxel (PTXL).The developed nanoformulations were evaluated for particle size, surface-charge, loading efficiency, particle density, in-vitro drug release, SEM/TEM, cytotoxicity assay, fluorescence uptake, HPLC quantitative cell uptake assay, flow cytometry, tubulin polymerization, and stability assessments.The developed pD-ANP-f nanoformulation (135.17 ± 7.39 nm; -2.05 ± 0.37 mV and 80.11 ± 4.39% entrapment) exhibited a pH-dependent drug release; remained stable in physiological pH, while rapid releasing PTXL under tumorous environment (pH 5.5). The cytotoxicity assay performed in cervical, breast, blood, and liver cancer cell lines showed pD-ANP-f to be strongly suppressing the growth of cancer cells. We investigated the fluorescence based intracellular trafficking and HPLC based cellular uptake of nanoformulated drug and the result indicates higher cellular uptake of pD-ANP-f compared to other formulations. pD-ANP-f prominently induced apoptosis (73.11 ± 3.84%) and higher polymerization of tubulins (59.73 ± 6.22%). DSSN nanoformulation was found to be extremely biocompatible (<1% hemolytic) compared to naked PTXL (19.22 ± 1.01%) as well as PTXL-dendrimer nanocomplex (8.29 ± 0.71%).DSSN strategy is a novel and promising platform for biomedical applications that can be effectively engaged for the delivery of drug/gene/siRNA targeting.

    View details for DOI 10.1007/s11095-014-1506-0

    View details for Web of Science ID 000349357300014

    View details for PubMedID 25205461