Expression of Endogenous Retroviral RNA in Prostate Tumors has Prognostic Value and Shows Differences among Americans of African Versus European/Middle Eastern Ancestry

Endogenous retroviruses (ERVs) are abundant, repetitive elements dispersed across the human genome and are implicated in various diseases. We investigated two potential roles for ERVs in prostate cancer (PCa). First, the PCa of Black Americans (BA) is diagnosed at an earlier median age and at a more advanced stage than the PCa of White Americans (WA). We used publicly available RNA-seq data from tumor-enriched samples of 27 BA and 65 WA PCa patients in order to identify 12 differentially expressed ERVs (padj < 0.1) and used a tissue microarray of the PCa cores from an independent set of BA and WA patients to validate the differential protein expression of one of these ERVs, ERV3-1 (p = 2.829 × 10−7). Second, we used 57 PCa tumors from patients of all ancestries from one hospital as a training set to identify the ERVs associated with time to biochemical relapse. A 29-ERV prognostic panel was then tested and validated on 35 separate PCa tumors from patients obtained in two different hospitals with a dramatic increase in prognostic power relative to clinical parameters alone (p = 7.4 × 10−11). In summary, ERV RNA expression differences in the prostate tumors of patients of different ancestries may be associated with dissimilarities in the mechanism of cancer progression. In addition, the correlation of expression of certain ERVs in prostate tumors with the risk of biochemical relapse indicates a possible role for ERV expression in cancer progression.

Delineating the Molecular Events Underlying Development of Prostate Cancer Variants with Neuroendocrine/Small Cell Carcinoma Characteristics

The treatment landscape of prostate cancer has changed dramatically following the advent of novel systemic therapies, most of which target the androgen receptor (AR). Agents such as abiraterone, enzalutamide, apalutamide, darolutamide were designed to further suppress androgen receptor signaling following gonadal suppression achieved by first-line androgen deprivation therapies. These potent AR targeting agents are increasingly used in the earlier stages of the disease spectrum with the goal of delaying disease progression and extending survival. Although these therapies are effective in controlling prostate tumors dependent on or addicted to AR signaling, prostate tumors surviving the onslaught of potent treatments may evolve and develop drug resistance. A substantial proportion of treatment failures can be explained by the development of treatment-induced aggressive prostate cancer variants such as neuroendocrine/small cell carcinoma. These emerging disease entities demand detailed characterization and precise definitions. We postulate that these treatment-induced prostate cancer entities should be defined molecularly to overcome the drawbacks associated with the current clinical and pathological definitions. A precise molecular definition conforms with current knowledge on the molecular evolution of this disease entity and will enable early detection and early intervention.

352 Target modulation within the tumor microenvironment (TME) by daratumumab (anti-CD38) but not edicotinib (CSF-1R inhibitor) in men with high-risk localized prostate cancer

BackgroundProstate cancer is ”immunologically cold,” with enrichment of myeloid populations, immunosuppressive cytokines, and few T cells within the tumor microenvironment (TME). CD38 is expressed on myeloid cells, T cells, plasma B cells, and NK cells. Macrophage colony-stimulating factor-1 receptor (CSF-1R) controls macrophage differentiation and function. We hypothesized that either anti-CD38 (daratumumab) or CSF-1R inhibitor (edicotinib) would be safe and well-tolerated for primary prostate cancer, with successful target modulation on immune populations within the TME.MethodsIn this single-center, open-label, presurgical study, patients were enrolled into Arm A (daratumumab, four weekly doses pre-surgery) or Arm B (edicotinib, orally daily for four weeks pre-surgery). Patients had high-risk localized or locally advanced prostate cancer (at least 1 core Gleason ≥8) appropriate for radical prostatectomy (RP), ≥3 biopsies involved with cancer, and no radiographic evidence of metastatic disease. Treated and untreated (Gleason-matched) fresh and formalin-fixed paraffin-embedded prostatectomy specimens and paired blood (PBMCs), bone marrow biopsies (BMBx) and aspirates (BMA) were evaluated for target modulation using IHC (prostate, BMBx) and flow cytometry (prostate, BMA, PBMCs). The primary endpoint was incidence of adverse events (AEs). The secondary endpoint was pathologic complete remission (pCR) rate.ResultsTwenty-five patients were treated (Arm A, n=15; Arm B, n=10) and completed four doses of daratumumab or four weeks of edicotinib prior to RP. The most common AEs were Arm A: daratumumab infusion reaction (33%, 5/15); Arm B: increased aspartate aminotransferase (40%, 4/10). Grade 3 related AEs in Arm A occurred in 3 patients (12%; infusion reaction, n=2; urticaria, n=1), with no Grade 4/5 related events. No ≥Grade 3 related AEs occurred in Arm B. All patients completed surgery, however no patients achieved pCR. IHC revealed lower density of CD38+ cells in daratumumab-treated vs. untreated prostate tumors and in patient-matched post-treatment vs. pre-treatment BMBx. Similarly, flow cytometry showed decreased frequency of CD38+ T cells and macrophages in daratumumab-treated vs. untreated prostate tumors and patient-matched post-treatment vs. pre-treatment PBMCs and BMAs. Edicotinib did not demonstrate an impact on CSF-1R+ immune cells in prostate, bone marrow, or PBMCs.ConclusionsDaratumumab and edicotinib were safe and well-tolerated as presurgical therapy for high-risk localized prostate cancer, with no pCRs. Evidence of target modulation was consistently observed in prostate tumors, bone marrow, and PBMCs for daratumumab, but not edicotinib. Myeloid-targeted agents such as daratumumab alone are insufficient to generate anti-tumor responses in prostate cancer.Trial RegistrationNCT03177460Ethics ApprovalThis study was approved by MD Anderson Cancer Center Institutional Review Board; protocol numbers 2017–0103 and PA13-0291.

Bone Marrow-Derived Mesenchymal Stem Cells Migrate toward Hormone-Insensitive Prostate Tumor Cells Expressing TGF-β via N-Cadherin

The prostate tumor microenvironment plays important roles in the metastasis and hormone-insensitive re-growth of tumor cells. Bone marrow-derived mesenchymal stem cells (BM-MSCs) are recruited into prostate tumors to facilitate tumor microenvironment formation. However, the specific intrinsic molecules mediating BM-MSCs’ migration to prostate tumors are unknown. BM-MSCs’ migration toward a conditioned medium (CM) of hormone-insensitive (PC3 and DU145) or hormone-sensitive (LNCaP) prostate tumor cells was investigated using a three-dimensional cell migration assay and a transwell migration assay. PC3 and DU145 expressed transforming growth factor-β (TGF-β), but LNCaP did not. Regardless of TGF-β expression, BM-MSCs migrated toward the CM of PC3, DU145, or LNCaP. The CM of PC3 or DU145 expressing TGF-β increased the phosphorylation of Smad2/3 in BM-MSCs. Inactivation of TGF-β signaling in BM-MSCs using TGF-β type 1 receptor (TGFBR1) inhibitors, SB505124, or SB431542 did not allow BM-MSCs to migrate toward the CM. The CM of PC3 or DU145 enhanced N-cadherin expression on BM-MSCs, but the LNCaP CM did not. SB505124, SB431542, and TGFBR1 knockdown prevented an increase in N-cadherin expression. N-cadherin knockdown inhibited the collective migration of BM-MSCs toward the PC3 CM. We identified N-cadherin as a mediator of BM-MSCs’ migration toward hormone-insensitive prostate tumor cells expressing TGF-β and introduced a novel strategy for controlling and re-engineering the prostate tumor microenvironment.

Cytotopic (Cyto-) IL-15 as a New Immunotherapy for Prostate Cancer: Recombinant Production in Escherichia coli and Purification

Interleukin-15 (IL-15) is a cytokine previously suggested as a potential immunotherapy for cancer treatment. IL-15 can effectively reduce tumor growth in many preclinical tumor models including prostate cancer. This is due to its ability to expand and activate immune cells, such as CD8+ T cells and natural killer cells. To increase the potency of IL-15, we have engineered a protein variant that can be modified to localize and be retained in tissues where it is administered. However, the production of recombinant IL-15, the purity, and correct refolding of the final protein is not always ideal. In the current study, we aimed to optimize the methodology for production and purification of a modified recombinant human IL-15 and investigate the efficacy of the produced protein in the treatment of prostate tumors. Human IL-15 with its polypeptide sequence modified at the C-terminus to enable thiol conjugation with membrane localizing peptides, was produced in E. coli and purified using mild denaturing conditions (2M urea) from a washing step or from solubilization of inclusion bodies. The purified protein from the wash fraction was conjugated to a myristoylated peptide to form a membrane-localizing IL-15 (cyto-IL-15). The efficacy of cyto-IL-15 was investigated in subcutaneous TRAMP-C2 prostate tumors in mice and compared with cyto-IL-15 derived from protein purified from inclusion bodies (cyto-IL-15 Gen). When mild denaturing conditions were used for purification, the largest amount of IL-15 was collected from the wash fraction and a smaller amount from inclusion bodies. The protein from the wash fraction was mainly present as a monomer, whereas the one from inclusion bodies formed homodimers and higher complexes. After cytotopic modification, the purified IL-showed great efficacy in delaying prostate tumor growth (∼50%) and increased mice survival by ∼1.8-fold compared with vehicle. This study demonstrates an alternative, inexpensive and efficient method to produce and purify a modified version of IL-15 using mild denaturing conditions. This IL-15, when cytotopically modified, showed great efficacy as a monotherapy in prostate tumors in mice further highlighting the potential of IL-15 as a cancer immunotherapy.

Prostate Cancer Delineation in MRI Images Based on Deep Learning: Quantitative Comparison and Promising Perspective

Prostate cancer is the most common malignant male tumor. Magnetic Resonance Imaging (MRI) plays a crucial role in the detection, diagnosis, and treatment of prostate cancer diseases. Computer-aided diagnosis systems can help doctors to analyze MRI images and detect prostate cancer earlier. One of the key stages of prostate cancer CAD systems is the automatic delineation of the prostate. Deep learning has recently demonstrated promising segmentation results with medical images. The purpose of this paper is to compare the state-of-the-art of deep learning-based approaches for prostate delineation in MRI images and discussing their limitations and strengths. Besides, we introduce a promising perspective for prostate tumor classification in MRI images. This perspective includes the use of the best segmentation model to detect the prostate tumors in MRI images. Then, we will employ the segmented images to extract the radiomics features that will be used to discriminate benign or malignant prostate tumors.