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321 Background: Sip-T is an FDA approved, autologous cellular immunotherapy for mCRPC, manufactured by activating peripheral blood mononuclear cells collected by apheresis and culturing them with PA2024 (PAP fused to human GM-CSF). Overall survival (OS) in mCRPC is positively correlated with key product parameters of sip-T: CD54 upregulation; CD54+ cell count; and total nucleated cell (TNC) count. Product parameters were amplified in men with earlier stage prostate cancer vs mCRPC, including increased T cell trafficking to the prostate (Fong L, JNCI 2014) and greater CD54 upregulation and larger immune responses (Antonarakis ES, Clin Can Res 2017). Methods: ProVENT (NCT03686683) will evaluate sip-T in men with Gleason grade 1/2 prostate adenocarcinoma receiving active surveillance (target, 450 men; randomized 2:1 to receiving sip-T or not). We evaluated apheresis and final key product parameters (CD54 upregulation; CD54+ cell count; and TNC count) for each infused product as well as cumulative values while also comparing with IMPACT (NCT00065442) study results. Results: This preliminary analysis describes data from the first 184 sip-T men in ProVENT. CD54 upregulation profiles were consistent between IMPACT and ProVent, peaking in week 2 products; however, values at each treatment week, and subsequently cumulative CD54 upregulation, were statistically significantly higher for ProVENT (P

e16126Background: Subclassificaiton of papillary RCC (pRCC) into type 1 and type 2 has been recognized as an independent negative prognostic factor. Little investigation has determined the effect o...

e16111 Background: Castrate resistant prostate cancer (CRPC) is the second leading cause of cancer-related death and nearly all men develop castrate resistance. Several new therapies, including enz...

e16028 Background: Castrate resistant prostate cancer (CRPC) is the second leading cause of cancer-related death in men in the developed world. Several new therapies, including taxane-based chemoth...

e16049 Background: Atypical small acinar proliferation (ASAP) is a diagnosis that occurs in about 1-2% of prostate biopsies. Approximately, 30-40% of patients with ASAP may develop prostate cancer....

158 Background: Potential benefits of neoadjuvant chemotherapy are tumor downstaging and treatment of micrometastatic disease. A prior study using docetaxel yielded no pathologic complete responses and concerns for increased operative morbidity. In Phase II studies, ixabepilone has promising activity in metastatic prostate cancer. Our study is a Phase I/II clinical trial evaluating neoadjuvant, weekly ixabepilone in men with high-risk prostate cancer opting for radical prostatectomy. Methods: Men with high risk prostate cancer defined as either Gleason 8-10, cT3 disease, high volume Gleason 4+3 and a palpable nodule or a PSA>20 ng/ml were eligible. Men received weekly ixabepilone 16-20/m2 for 12-16 weeks prior to surgery. Fifteen men underwent robotic prostatectomy; one patient who had an open prostatectomy. Initial PSA response, post-operative PSA values, pathology, and evaluation of adverse events were recorded. Results: We enrolled 16 men with a mean follow-up of 15.25 months at time of review. All had pretreatment Gleason scores of 4+3 or higher. With neoadjuvant treatment, PSA values decreased in 14/16 men (mean 46.8%); increased in 2/16 men. None reached an undetectable pre-operative PSA. Nine men experienced an adverse event requiring dose modification or cessation of chemotherapy (neuropathy or allergic reaction). Only 5/16 men completed planned treatment. Mean operative time, EBL, and hospital stay were 189 minutes, 184mL, and1.5 days, respectively; all consistent with institutional and national norms. Post surgery 15/16 (94%) had pT3 disease, 8/16 (50%) had a positive surgical margin and 2/16 (12.5%) had positive regional lymph nodes. There were no pathologic complete responses. Only 1/16 (6.25%) had a biochemical relapse. Conclusions: While a PSA response is achieved, there is substantial toxicity with neoadjuvant weekly ixabepilone. Men were able to undergo prostatectomy without increased morbidity after neoadjuvant therapy. Extracapsular extension and positive surgical margins remained common in this population with high-risk disease. Assessment of biochemical recurrence rates and time to treatment failure will require longer, planned follow-up.

e16076 Background: Microvesicles have been a subject of research for many years. Recent work has focused on the potential for cancer vaccines via microvesicles. It has also been demonstrated that various cell-specific phenotypes can be transferred from one cell type to another through microvesicle transfer. Studies in our laboratory have demonstrated that co-culture of murine lung tissue with marrow cells across a cell impermeable membrane can induce elevations in lung-specific mRNA expression in human donor marrow stem cells. Our objective is to determine whether there is transfer of genetic or transcriptional factors via microvesicles from human prostate cancer cells to fresh human marrow cells. Methods: Fresh prostate tissue was harvested from surgical specimens following radical retropubic prostatectomy. Samples were histologically confirmed to contain prostatic adenocarcinoma. Co-cultures were established using a transwell system in which 0.05–0.100 grams of prostate tissue was minced and co-cultured with 1–3 million normal, human donor marrow cells for 2–7 days. Marrow not co-cultured with tumorserved as a control. Target cells were collected and total RNA was analyzed for prostate-specific gene expression byReal Time RT-PCR. Fold differences in expression of the genes were analyzed, using TaqMan®, gene assays (Applied Biosystems) and were expressed in relation to the marrow control. Results: We have observed significant increases in gene expression in marrow cells co-cultured with prostate tumor cells (Gleason grades 6–9). Variable increases in expression were seen in 3 patient samples, as high as 7-fold for ERG, greater than 10-fold for ACPP and greater than 100-fold for STEAP, PART, TMPRSS2, PSCA and ETV1. Conclusions: These studies demonstrate that prostate specific genes are present in fresh human marrow cells after co-culture with tumor tissue. This establishes a base to begin evaluating the significance of microvesicle-mediated genetic transfer, mechanisms of transfer and therapeutic options for blocking or manipulating such transfer to influence the disease process. No significant financial relationships to disclose.