Inflammatory mechanisms influence tumor development and metastatic progression1. Of interest is the role of such mechanisms in metastatic spread of tumors whose etiology does not involve pre-existing inflammation or infection, such as breast and prostate cancers. We found that prostate cancer metastasis is associated with lymphocyte infiltration into advanced tumors and elevated expression of the tumor necrosis factor (TNF) family members receptor activator of NF-κB (RANK) ligand (RANKL) and lymphotoxin (LT)2. But the source of RANKL and its role in metastasis were not established. RANKL and its receptor RANK control proliferation of mammary lobuloalveolar cells during pregnancy3 through activation of IκB kinase α (IKKα)4, a protein kinase that is required for self-renewal of mammary cancer progenitors5 and prostate cancer metastasis2. We therefore examined whether RANKL, RANK and IKKα are also involved in mammary/breast cancer metastasis. Indeed, RANK signaling in mammary carcinoma cells that overexpress the ErbB2 (c-Neu) proto-oncogene6, which is frequently amplified in metastatic human breast cancers7,8, was important for pulmonary metastasis. Metastatic spread of ErbB2-transformed carcinoma cells was also dependent on CD4+CD25+ T cells, whose major pro-metastatic function appeared to be RANKL production. RANKL-producing T cells were mainly FoxP3+ and found in close proximity to smooth muscle actin (SMA)-positive stromal cells in mouse and human breast cancers. The T cell-dependence of pulmonary metastasis was replaced by administration of exogenous RANKL, a procedure that also stimulated pulmonary metastasis of RANK-positive human breast carcinoma cells. These results are consistent with the adverse prognostic impact of tumor-infiltrating CD4+ or FoxP3+ T cells on human breast cancer9,10 and suggest that targeting of RANKL-RANK signaling can be used in conjunction with other therapies to prevent subsequent metastatic disease.

Cancer-associated genetic alterations induce expression of tumor antigens which can activate CD8+ cytotoxic T cells (CTL), but the microenvironment of established tumors promotes immune tolerance through poorly understood mechanisms1,2. Recently developed therapeutics that overcome tolerogenic mechanisms activate tumor-directed CTL and are effective in some human cancers1. Immune mechanisms also affect treatment outcome and certain chemotherapeutic drugs stimulate cancer-specific immune responses by inducing immunogenic cell death (ICD) and other effector mechanisms3,4. Our previous studies revealed that B lymphocytes recruited by CXCL13 into prostate cancer (PC) promote castrate-resistant PC (CRPC) by producing lymphotoxin (LT) which activates an IKKα-Bmi1 module in PC stem cells5,6. Since CRPC is refractory to most therapies, we examined B cell involvement in acquisition of chemotherapy resistance. We focused this study on oxaliplatin, an immunogenic chemotherapeutic3,4 that is effective in aggressive PC7. We found that B cells modulate the response to low dose oxaliplatin, which by inducing ICD promotes tumor-directed CTL activation. Three different mouse PC models were refractory to oxaliplatin unless genetically or pharmacologically depleted of B cells. The critical immunosuppressive B cells are plasmocytes that express IgA, IL-10 and PD-L1, whose appearance depends on TGFβ-receptor (TGFβR) signaling. Elimination of these cells, which also infiltrate human therapy-resistant PC, allows CTL-dependent eradication of oxaliplatin-treated tumors.

It is becoming increasingly clear that inflammation influences prostate cancer (PCa) development and that immune cells are among the primary drivers of this effect. This information has launched numerous clinical trials testing immunotherapy drugs in PCa patients. The results of these studies are promising but have yet to generate a complete response. Importantly, the precise immune profile that determines clinical outcome remains unresolved. Individual immune cell types are divided into various functional subsets whose effects on tumor development may differ depending on their particular phenotype and functional status, which is often shaped by the tumor microenvironment. Thus, this review aims to examine the current knowledge regarding the role of inflammation and specific immune cell types in mediating PCa progression to assist in directing and optimizing immunotherapy targets, regimens, and responses and to uncover areas in which further research is needed. Finally, a summary of ongoing immunotherapy clinical trials in PCa is provided.

BackgroundThe presence of increased B-cell tumor infiltrating lymphocytes (TILs) was seen in mouse prostate cancer (PCa) but has not been fully documented in human PCa. We, therefore, investigated the density of infiltrating B cells within human PCa utilizing a quantitative computational method.MethodsArchived radical prostatectomy specimens from 53 patients with known clinical outcome and D’Amico risk category were obtained and immunohistochemically (IHC) stained for the B cell marker, CD20. Slides were reviewed by a genitourinary pathologist who manually delineated the tumoral regions of PCa. Slides were digitally scanned and a computer algorithm quantified the area of CD20 stained B-cells as a measure of B cell density within the outlined regions of prostate cancer (intra-tumoral region), versus extra-tumoral prostate tissue. Correlations were analyzed between B-cell density and demographic and clinical variables, including D’Amico risk groups and disease recurrence.ResultsFor the entire cohort, the mean intra-tumoral B cell density was higher (3.22 SE = 0.29) than in the extra-tumoral region of each prostatectomy section (2.24, SE = 0.19) (paired t test; P < 0.001). When analyzed according to D’Amico risk group, the intra-tumoral B cell infiltration in low risk (0.0377 vs. 0.0246; p = 0.151) and intermediate risk (0.0260 vs. 0.0214; p = 0.579) patient prostatectomy specimens did not show significantly more B-cells within the PCa tumor. However, patient specimens from the high-risk group (0.0301 vs. 0.0197; p < 0.001) and from those who eventually had PCa recurrence or progression (0.0343 vs. 0.0246; p = 0.019) did show significantly more intra-tumoral CD20+ B-cell staining. Extent of B-cell infiltration in the prostatectomy specimens did not correlate with any other clinical parameters.ConclusionsOur study shows that higher B-cell infiltration was present within the intra-tumoral PCa regions compared to the extra-tumoral benign prostate tissue regions in prostatectomy sections. For this study we developed a new method to measure B-cells using computer-assisted digitized image analysis. Accurate, consistent quantitation of B-cells in prostatectomy specimens is essential for future clinical trials evaluating the effect of B cell ablating antibodies. The interaction of B-cells and PCa may serve as the basis for new therapeutic targets.

SUMMARY IκB kinase α (IKKα) activity is required for ErbB2-induced mammary tumorigenesis. Here, we show that IKKα and its activator, NF-κB-inducing kinase (NIK), support the expansion of tumor-initiating cells (TICs) that copurify with a CD24medCD49fhi population from premalignant ErbB2-expressing mammary glands. Upon activation, IKKα enters the nucleus, phosphorylates the cyclin-dependent kinase (CDK) inhibitor p27/Kip1, and stimulates its nuclear export or exclusion. Reduced p27 expression rescues mammary tumorigenesis in mice deficient in IKKα kinase activity and restores TIC self-renewal. IKKα is also likely to be involved in human breast cancer, where its expression shows an inverse correlation with metastasis-free survival, and its presence in the nucleus of invasive ductal carcinomas (IDCs) is associated with decreased nuclear p27 abundance.

Androgen-deprived prostate cancer (PCa) is infiltrated by B lymphocytes that produce cytokines that activate IkB kinase a (IKKa) to accelerate the emergence of castrationresistant tumors. We now demonstrate that infiltrating B lymphocytes and IKKa are also required for androgendependent expansion of epithelial progenitors responsible for prostate regeneration. In these cells and in PCa cells, IKKa phosphorylates transcription factor E2F1 on a site that promotes its nuclear translocation, association with the coactivator CBP, and recruitment to critical genomic targets that include Bmi1, a key regulator of normal and cancerous prostate stem cell renewal. The IKKa-BMI1 pathway is also activated in human PCa.

We conclude that prednisone is not the cause for increased body fat following transplantation; however, it may contribute to lower spontaneous improvements in exercise capacity possibly by limiting increases in muscle strength. The low exercise capacity in all transplant recipients studied at 1 year suggests a need for exercise training to optimize physical functioning following transplant.

IntroductionProstate cancer bone metastasis occurs in 50-90% of men with advanced disease for which there is no cure. Bone metastasis leads to debilitating fractures and severe bone pain. It is associated with therapy resistance and rapid decline. Androgen deprivation therapy (ADT) is standard of care for advanced prostate cancer, however, bone metastatic prostate cancer (PCa) often becomes resistant to ADT. There are few pre-clinical models to understand the interaction between the bone microenvironment and prostate cancer. Here we report the castrate resistant growth in the bone niche of PCSD1, a patient-derived intra-femoral xenograft model of prostate bone metastatic cancer treated with the anti-androgen, bicalutamide.MethodsPCSD1 bone-niche model was derived from a human prostate cancer femoral metastasis resected during hemiarthroplasty and serially transplanted into Rag2−/−;γc−/− mice intra-femorally (IF) or sub-cutaneously (SC). At 5 weeks post-transplantation mice received bicalutamide or vehicle control for 18 days. Tumor growth of PCSD1 was measured with calipers. PSA expression in PCSD1 xenograft tumors was determined using quantitative RT-PCR and immunohistochemistry. Expression of AR and PSMA, were also determined with qPCR.ResultsPCSD1 xenograft tumor growth capacity was 24 fold greater in the bone (intra-femoral, IF) than in the soft tissue (sub-cutaneous, SC) microenvironment. Treatment with the anti-androgen, bicalutamide, inhibited tumor growth in the sub-cutaneous transplantation site. However, bicalutamide was ineffective in suppressing PCSD1 tumor growth in the bone-niche. Nevertheless, bicalutamide treatment of intra-femoral tumors significantly reduced PSA expression (p < =0.008) and increased AR (p < =0.032) relative to control.ConclusionsPCSD1 tumors were castrate resistant when growing in the bone-niche compared to soft tissue. Bicalutamide had little effect on reducing tumor burden in the bone yet still decreased tumor PSA expression and increased AR expression, thus, this model closely recapitulated castrate-resistant, human prostate cancer bone metastatic disease. PCSD1 is a new primary prostate cancer bone metastasis-derived xenograft model to study bone metastatic disease and for pre-clinical drug development of novel therapies for inhibiting therapy resistant prostate cancer growth in the bone-niche.