Publications

5091 Background: CHAARTED criteria using CT and bone scan are widely recognized as prognostic in metastatic, hormone-sensitive prostate cancer (mHSPC) and can guide decisions about treatment, including intensification. However, clinicians are increasingly using PSMA PET/CT (PSMA-PET) instead of conventional imaging. Currently, PSMA-PET criteria for identifying poor prognostic mHSPC has limited evidence. The aim of this study is to identify features on PSMA PET/CT that correlate to progression free survival (PFS) and overall survival (OS) in the context of CHAARTED criteria in an ENZAMET sub-cohort. Methods: ENZAMET (ANZUP 1304, NCT02446405) is an international, open-label, randomized, phase 3 trial. Eligible participants had mHSPC evident on CT and/or bone scan. Participants (pts) were randomly assigned (1:1) to receive testosterone suppression plus enzalutamide or a non-steroidal antiandrogen (NSAA). Pts who underwent PSMA-PET prior to study enrolment were identified for this sub-study. Imaging (PSMA-PET, CT, bone scan) were de-identified, and centrally evaluated by three imaging experts blinded to clinical outcomes for number, site, and intensity of metastatic deposits. Additional correlative findings on bone scan and PSMA-PET/CT were determined. A semi-automated quantitative imaging analysis was undertaken to derive PSMA-total tumor volume (PSMA-TTV). The analysis evaluated the association between PSMA-TTV (analysed continuously and as quartiles Q1-3 vs Q4), site (lymph node, bone, viscera) with PFS, OS, and CHAARTED criteria. Kaplan-Meier survival estimates, log-rank tests, and Cox regression after adjusting for treatment arm were used for analysis. Results: 100 pts (51 enzalutamide, 49 control NSAA) had a PSMA-PET/CT prior to enrolment. In this sub-cohort, median age was 69 years, 36 were synchronous, 74 patients were low volume on CHAARTED criteria. On PSMA-PET 19 pts had bone only disease, 37 had lymph node (LN) only, 33 bone and LN and 9 visceral involvement. In 54 pts with bone involvement on PSMA-PET, 53 had concordant findings on bone scan. Median PSMA TTV in the study cohort was 28 mL (61 mL vs 22 mL in CHAARTED high vs low volume) with the highest PSMA TTV quartile (Q4) >71mL. 5-year PFS for PSMA TTV Q4 vs Q1-3 was 36% vs 61% (p=0.011), with HR per doubling of TTV = 1.19 (95%CI: 1.03 – 1.38). In the pts with CHAARTED criteria low volume mHSPC, 5-year PFS for PSMA TTV Q4 vs Q1-3 was 21% vs 57% (p<0.001). 5-year OS for PSMA TTV Q4 vs Q1-3 was 60% vs 74% (p=0.18) with HR per doubling of TTV = 1.10 (95%CI: 0.91 – 1.32). Conclusions: PSMA-TTV is associated with PFS in mHSPC in this ENZAMET sub-cohort with the highest volume quartile (>71mls) showing significantly shorter PFS, including within the CHAARTED criteria low volume cohort. Further validation of PSMA-TTV as a prognostic biomarker with potential to identify patients for intensification is warranted in larger mHSPC cohorts. Clinical trial information: NCT02446405 .

Abstract Hyperactivation of oncogenic pathways downstream of RAS and PI3K/AKT in normal cells induces a senescence-like phenotype that acts as a tumor-suppressive mechanism that must be overcome during transformation. We previously demonstrated that AKT-induced senescence (AIS) is associated with profound transcriptional and metabolic changes. Here, we demonstrate that human fibroblasts undergoing AIS display increased Cystathionine-β-synthase (CBS) expression and consequent activation of the transsulfuration pathway controlling hydrogen sulfide (H2S) and glutathione (GSH) metabolism. Activated transsulfuration pathway during AIS maintenance enhances the antioxidant capacity, protecting senescent cells from ROS-induced cell death via GSH and H2S. Importantly, CBS depletion allows cells that have undergone AIS to escape senescence and re-enter the cell cycle, indicating the importance of CBS activity in maintaining AIS. Mechanistically, we show this restoration of proliferation is mediated through suppressing mitochondrial respiration and reactive oxygen species (ROS) production and increasing GSH metabolism. These findings implicate a potential tumor-suppressive role for CBS in cells with inappropriately activated PI3K/AKT signaling. Consistent with this concept, in human gastric cancer cells with activated PI3K/AKT signaling, we demonstrate that CBS expression is suppressed due to promoter hypermethylation. CBS loss cooperates with activated PI3K/AKT signaling in promoting anchorage-independent growth of gastric epithelial cells, while CBS restoration suppresses the growth of gastric tumors in vivo . Taken together, we find that CBS is a novel regulator of AIS and a potential tumor suppressor in PI3K/AKT-driven gastric cancers, providing a new exploitable metabolic vulnerability in these cancers.

Prostate cancer (PC) is the most common cancer in men. Elevated levels of E3 ligase, E6-Associated Protein (E6AP) were previously linked to PC, consistent with increased protein expression in a subset of PC patients. In cancers, irregular E3 ligase activity drives proteasomal degradation of tumor suppressor proteins. Accordingly, E3 ligase inhibitors define a rational therapy to restore tumor suppression. The relevant tumor suppressors targeted by E6AP in PC are yet to be fully identified. In this study we show that p27, a key cell cycle regulator, is a target of E6AP in PC. Down regulation of E6AP increases p27 expression and enhances its nuclear accumulation in PC. We demonstrate that E6AP regulates p27 expression by inhibiting its transcription in an E2F1-dependent manner. Concomitant knockdown of E6AP and p27 partially restores PC cell growth, supporting the contribution of p27 to the overall effect of E6AP on prostate tumorigenesis. Overall, we unravelled the E6AP-p27 axis as a new promoter of PC, exposing an attractive target for therapy through the restoration of tumor suppression.

77 Background: [ 177 Lu]Lu-PSMA (LuPSMA) is currently FDA-approved for use in the post-taxane, post-antiandrogen setting in pts with mCRPC. Little is known about the efficacy of treatment in pts with subsequent progression after LuPSMA. In this single-centre retrospective analysis, we evaluated efficacy of first subsequent therapy following LuPSMA. Methods: 234 mCRPC pts who received LuPSMA at the Peter MacCallum Cancer Centre from 2015-2022 were analysed. Pts were excluded if they did not receive any subsequent treatment (n=136), if they received the initial course of LuPSMA in combination with another therapy (n=10), or if insufficient follow-up data were available (n=15).Retreatment withLuPSMA was considered a subsequent line of therapy. Data collected included 50% PSA response rate (PSA-RR), PSA-progression free survival (PSA-PFS) and overall survival (OS). Survival outcomes were calculated using Kaplan-Meier analysis. Results: Of 73 evaluable pts, 32 were retreated with LuPSMA (median 2 cycles); and 41 commenced a new line of systemic therapy. In the LuPSMA retreatment group, the PSA-RR was 44%, median PSA-PFS was 3.8 months and median OS 14.8 months. In pts who changed to a new line of treatment, cabazitaxel was the most commonly prescribed therapy (n=25), followed by docetaxel (n=7), and single-agent carboplatin (n=4), in addition to carboplatin/etoposide, mitoxantrone, olaparib, capecitabine and a clinical trial (n=1 for each). PSA-RR was 12%, median PSA-PFS was 3.5 months and median OS 6.6 months. Conclusions: This retrospective data demonstrates that retreatment with LuPSMA is associated with benefit, though this is reduced compared to initial treatment. In our cohort of pts who commenced a new line of therapy, most were not suitable for retreatment with LuPSMA, potentially reflecting de-differentiated and more aggressive disease phenotypes. In those not suitable for LuPSMA retreatment, other systemic therapy appears to have limited benefit, highlighting the lack of effective salvage options and raising questions about treatment sequencing. [Table: see text]

Background: Alpiniae oxyphyllae Fructus (AOF), a traditional Chinese medicine (TCM), is widely used in the treatment of urinary, gastrointestinal and neurologic diseases in China. Although terpenoids are the main active ingredients of AOF, there are few researches on their pharmacokinetics and metabolism. Methods: In this study, a sensitive, rapid, accurate and novel ultra high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was established to evaluate the pharmacokinetic behavior of five terpenoids (oxyphyllenodiol B, (4S*,5E,10R*)-7-oxo-tri-nor-eudesm-5-en-4β-ol, 7-epi-teucrenone, (+)- (4R,5S,7R)-13-hydroxynootkatone, (E)-labda-12,14-dien-15(16)-olide-17-oic acid) in rats after oral administration of AOF extracts. 27 metabolic metabolites of the five terpenoids were identified by ultra high performance liquid chromatography -Q Exactive hybrid quadrupole-orbitrap high-resolution accurate mass spectrometry (UHPLC-Q-Orbitrap HRMS) based on precise mass and fragment ions. Results: The established pharmacokinetic analysis method showed good linearity over a wide concentration range, and the lower quantitative limit (LLOQ) ranged from 0.97 to 4.25 ng/mL. Other validation parameters were within the acceptable range. In addition, 27 metabolites were identified in plasma, urine and feces samples, and the metabolic pathways of five terpenoids were mainly focused on glucoside conjugation, dehydration, desaturation and glycine conjugation. Conclusion: This is the first study on the pharmacokinetics and metabolism of five terpenoids in AOF, illuminating the disposal process of terpenoids in vivo. It was expected that the results of this study would provide some references for the apprehension of the action mechanism and the further pharmacological study of five terpenoids in AOF.