Dissecting Oxygen Sensing and PTEN Loss in FDG/Fluciclovine Uptake as Markers of PSMA Radioligand Therapy Resistance - PROJECT SUMMARY: Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) has transformed staging and therapeutic selection in advanced prostate cancer, but responses to PSMA-directed radioligand therapy (RLT) remain heterogeneous. A substantial fraction of patients lack sufficient PSMA expression, and many PSMA-positive tumors develop resistance. Hypoxia/HIF signaling and PTEN loss are implicated in suppressing PSMA surface availability while inducing glucose and amino-acid transport (GLUT1, LAT1/ASCT2), resulting in elevated 18F-FDG and 18F-fluciclovine uptake and discordant PET phenotypes that likely contribute to RLT resistance. The long-term objective of this proposal is to deliver mechanism-anchored imaging markers and therapeutic strategies that improve patient selection, monitoring, and outcomes with PSMA-RLT, aligning with the NCI mission to reduce the burden of cancer. In Aim 1, I will define how oxygen sensing regulates PSMA maturation and localization by modulating HIF-1/2 in prostate cancer cell lines, organoids, and patient-derived tissues, and by integrating spatial transcriptomics/proteomics to colocalize hypoxia signatures with PSMA localization and transporter expression. In Aim 2, I will determine how PTEN loss perturbs microtubule/vesicular trafficking and PI3K/AKT/mTOR-dependent metabolic rewiring to drive FDG and fluciclovine uptake, using isogenic models, live-cell trafficking and endo/exocytosis assays, N-glycan processing analyses, and rescue with AKT/mTOR inhibition or microtubule-targeting. In Aim 3, I will test whether HIF- -478) or LAT1 inhibition (JPH203) remodels tracer uptake, restores surface PSMA, and re-sensitizes tumors to 177Lu-PSMA in pharmacodynamic PET shifts. I will emphasize rigor and reproducibility through standardized multi-tracer PET metrics and radiomics, spatial multi-omics linked to trafficking and glycoproteomic mechanisms, prespecified analysis plans, version-controlled code, and blinded QC. During the mentored K99 phase, I will receive focused training in spatial biology, image analysis, and quantitative PET analytics under Dr. Himisha Beltran (primary mentor) and an advisory committee including Drs. William Kaelin, Myles Brown, and Heather Jacene, positioning me to launch an independent imaging-theranostics program in the R00 phase. This project prioritizes human-based approaches including rapid autopsy tissues with linked PET data, organoids, and cell-based assays to define metabolic tracer phenotypes. Vertebrate animal studies are limited to focused Aim 3 experiments using the minimum number necessary to evaluate integrated in vivo endpoints that cannot be modeled in tissues or organoids, including radioligand biodistribution, tumor response, and survival. The expected outcome is a set of validated imaging markers and mechanism-based therapeutic strategies that reduce treatment failure by identifying PSMA-negative biology, guiding optimal use of FDG or fluciclovine, and resensitizing tumors to PSMA-RLT.
