acid-phosphatase and Prostatic-Neoplasms--Castration-Resistant

Sipuleucel-T, an autologous cellular immunotherapy manufactured from antigen-presenting cells primed to recognize prostatic acid phosphatase, was the first immunotherapy product approved by the US FDA. It was approved for men with asymptomatic or minimally symptomatic metastatic castration-resistant prostate cancer after it was shown to provide a survival advantage. Additional studies have examined its use in other clinical settings and in combination with other approved and investigational immunotherapy agents. This review will discuss the pivotal trials leading to approval, will outline some of the biomarkers associated with its efficacy and will review some of the ongoing combination strategies. Maximizing the efficacy of sipuleucel-T through better patient selection or through combination approaches remains the challenge of the future.

Topics: Acid Phosphatase; Animals; Antineoplastic Agents; Biomarkers, Tumor; Cancer Vaccines; Clinical Trials as Topic; Combined Modality Therapy; Humans; Immunotherapy, Adoptive; Male; Prostatic Neoplasms, Castration-Resistant; Tissue Extracts

Sipuleucel-T is an autologous cellular immunotherapy, administered as three infusions, for metastatic castration-resistant prostate cancer (mCRPC). Sipuleucel-T induces T- and B-cell responses to prostatic acid phosphatase (PAP), correlating to improved survival. The long-term impact of sipuleucel-T on tumor antigen-specific immunologic memory remains unknown, in particular, B-cell responses, as measured by antigen-specific antibody responses and B-cell receptor (BCR) sequences. To evaluate whether sipuleucel-T could induce long-term immunologic memory, we examined circulating B-cell responses before and after sipuleucel-T treatment in two groups of patients with mCRPC: those who had previously received sipuleucel-T (treated; median, 8.9 years since the previous treatment) versus those who had not (naïve). Before re-treatment, previously treated patients exhibited persistent antibody responses as well as more focused and convergent BCR repertoires with distinct V(D)J gene usage compared with naïve patients. After re-treatment, previously treated patients maintained high-frequency clones and developed more convergent BCRs at earlier time points unlike naïve patients. With the first sipuleucel-T infusion specifically, previously treated patients had less shuffling within the 100 most abundant baseline clones. In contrast, naïve patients exhibited great BCR turnover with a continued influx of new B-cell clones. Social network analysis showed that previously treated patients had more highly organized B-cell repertoires, consistent with greater clonal maturation. Higher treatment-induced BCR clonality correlated with longer survival for naïve patients. These results demonstrated the capacity of sipuleucel-T to induce long-term immune memory and lasting changes to the B-cell repertoire.

Topics: Acid Phosphatase; Aged; Aged, 80 and over; Antigens, Neoplasm; B-Lymphocytes; Humans; Immunotherapy; Male; Middle Aged; Prostatic Neoplasms, Castration-Resistant; Survival Rate; Tissue Extracts

Prostatic acid phosphatase (PAP) is a prostate tumor antigen, and the target of the only FDA-approved anti-tumor vaccine, sipuleucel-T. We have previously reported in two clinical trials that a DNA vaccine encoding PAP (pTVG-HP) could elicit PAP-specific, Th1-biased T cells in patients with PSA-recurrent prostate cancer. In the current pilot trial we sought to evaluate whether this vaccine could augment PAP-specific immunity when used as a booster to immunization with sipuleucel-T in patients with metastatic, castration-resistant prostate cancer (mCRPC).. Eigthteen patients with mCRPC were randomized to receive sipuleucel-T alone or followed by intradermal immunization with pTVG-HP DNA vaccine. Patients were followed for time to progression, and immune monitoring was conducted at defined intervals.. Overall, patients were followed for a median of 24 months. 11/18 patients completed treatments as per protocol. No treatment-associated events > grade 2 were observed. Th1-biased PAP-specific T-cell responses were detected in 11/18 individuals, and were not statistically different between study arms. Higher titer antibody responses to PAP were detectable in patients who received pTVG-HP booster immunizations. Median time to progression was less than 6 months and not statistically different between study arms. The median overall survival for all patients was 28 months.. These findings suggest that prime-boost vaccination can augment and diversify the type of immunity elicited with anti-tumor vaccination in terms of T-cell and humoral immunity. Future studies will explore DNA as priming immunization rather than a booster immunization.. NCT01706458 .

Topics: Acid Phosphatase; Aged; Aged, 80 and over; Antigens, Neoplasm; Cancer Vaccines; Humans; Male; Prostatic Neoplasms, Castration-Resistant; Tissue Extracts; Vaccination; Vaccines, DNA

Topics: Acid Phosphatase; CD8-Positive T-Lymphocytes; Cell Line, Tumor; Cell Proliferation; Clinical Trials as Topic; Gene Expression Regulation, Neoplastic; Granulocyte-Macrophage Colony-Stimulating Factor; Humans; Lysosomal-Associated Membrane Protein 1; Male; Neoplasm Metastasis; Neoplasms, Hormone-Dependent; Prostatic Neoplasms, Castration-Resistant; Recombinant Fusion Proteins; T-Lymphocytes, Cytotoxic; Tissue Extracts

While androgen deprivation therapy (ADT) reduces tumor burden, autocrine growth factor loops such as human epidermal growth factor receptor 2 (HER2/ErbB-2/neu) have been proposed to contribute to prostate cancer (PCa) survival and relapse. However, the role of ErbB-2 in regulating androgen-sensitive (AS) and castration-resistant (CR) cell proliferation remains unclear. Here, we determined the role of ErbB-2 in PCa progression and survival under steroid-reduced conditions using two independent PCa cell progression models. In AR-positive androgen-independent (AI) PCa cells that exhibit the CR phenotype, ErbB-2 was constitutively activated, compared to corresponding AS PCa cells. In AS LNCaP C-33 cells, androgen-induced ErbB-2 activation through ERK1/2 mediates PCa cell proliferation. Further, the ErbB-2-specific but not EGFR-specific inhibitor suppresses basal and androgen-stimulated cell proliferation and also blocks ERK1/2 activation. ErbB-2 ectopic expression and cPAcP siRNA transfection of LNCaP C-33 cells each increases ErbB-2 tyrosine phosphorylation, correlating with increased AI PSA secretion and cell proliferation. Conversely, trapping ErbB-2 by transfected endoplasmic reticulum-targeting ScFv5R expression vector abolished DHT-induced LNCaP C-33 cell growth. Moreover, inhibition of ErbB-2 but not EGFR in AI LNCaP C-81 and MDA PCa2b-AI PCa cells significantly abolished AI cell growth. In contrast to androgens via ErbB-2/ERK1/2 signaling in AS PCa cells, the inhibition of ErbB-2 abrogated AI cell proliferation by inhibiting the cell survival protein Akt in those AI cells. These results suggest that ErbB-2 is a prominent player in mediating the ligand-dependent and -independent activation of AR in AS and AI/CR PCa cells respectively for PCa progression and survival.

Topics: Acid Phosphatase; Androgen Antagonists; Cell Line, Tumor; Cell Proliferation; Cell Survival; Endoplasmic Reticulum; ErbB Receptors; Extracellular Signal-Regulated MAP Kinases; Humans; Kallikreins; Male; Phosphorylation; Prostate-Specific Antigen; Prostatic Neoplasms, Castration-Resistant; Protein-Tyrosine Kinases; Proto-Oncogene Proteins c-akt; Receptor, ErbB-2; Receptors, Androgen; RNA Interference; RNA, Small Interfering; Signal Transduction

We have previously reported that a DNA vaccine encoding prostatic acid phosphatase (PAP) could elicit PAP-specific T cells in patients with early recurrent prostate cancer. In the current pilot trial, we sought to evaluate whether prolonged immunization with regular booster immunizations, or "personalized" schedules of immunization determined using real-time immune monitoring, could elicit persistent, antigen-specific T cells, and whether treatment was associated with changes in PSA doubling time (PSA DT).. Sixteen patients with castration-resistant, nonmetastatic prostate cancer received six immunizations at 2-week intervals and then either quarterly (arm 1) or as determined by multiparameter immune monitoring (arm 2).. Patients were on study a median of 16 months; four received 24 vaccinations. Only one event associated with treatment >grade 2 was observed. Six of 16 (38%) remained metastasis-free at 2 years. PAP-specific T cells were elicited in 12 of 16 (75%), predominantly of a Th1 phenotype, which persisted in frequency and phenotype for at least 1 year. IFNγ-secreting T-cell responses measured by ELISPOT were detectable in 5 of 13 individuals at 1 year, and this was not statistically different between study arms. The overall median fold change in PSA DT from pretreatment to posttreatment was 1.6 (range, 0.6-7.0; P = 0.036).. Repetitive immunization with a plasmid DNA vaccine was safe and elicited Th1-biased antigen-specific T cells that persisted over time. Modifications in the immunization schedule based on real-time immune monitoring did not increase the frequency of patients developing effector and memory T-cell responses with this DNA vaccine.

Topics: Acid Phosphatase; Adenocarcinoma; Aged; Aged, 80 and over; Cancer Vaccines; Humans; Immunization; Immunization Schedule; Male; Middle Aged; Plasmids; Prostate-Specific Antigen; Prostatic Neoplasms, Castration-Resistant; Treatment Outcome; Vaccines, DNA