Early generation of a precursor CD8 T cell that can adapt to acute or chronic viral infection

Virus specific PD-1+ TCF-1+ TOX+ stem-like CD8+ T cells are essential for maintaining T cell responses during chronic infection and are also critical for PD-1 directed immunotherapy. In this study we have used the mouse model of chronic LCMV infection to examine when these virus specific stem-like CD8+ T cells are generated during the course of chronic infection and what is the role of antigen in maintaining the stem-like program. We found that these stem-like CD8+ T cells are generated early (day 5) during chronic infection and that antigen is essential for maintaining their stem-like program. This early generation of stem-like CD8+ T cells suggested that the fate commitment to this cell population was agnostic to the eventual outcome of infection and the immune system prepares a priori for a potential chronic infection. Indeed, we found that an identical virus specific stem-cell like CD8+ T cell population was also generated during acute LCMV infection but these cells were lost once the virus was cleared. To determine the fate of these early PD-1+TCF-1+TOX+ stem-like CD8+ T cells that are generated during both acute and chronic LCMV infection we set up two reciprocal adoptive transfer experiments. In the first experiment we transferred day 5 stem-like CD8+ T cells from chronically infected into acutely infected mice and examined their differentiation after viral clearance. We found that these early stem-like CD8+ T cells downregulated canonical markers of the chronic stem-like CD8+ T cells and expressed markers (CD127 and CD62L) associated with central memory CD8+ T cells. In the second experiment, we transferred day 5 stem-like cells from acutely infected mice into chronically infected mice and found that these CD8+ T cells could function like resource cells after transfer into a chronic environment by generating effector CD8+ T cells in both lymphoid and non-lymphoid tissues while also maintaining the number of stem-like CD8+ T cells. These findings provide insight into the generation and maintenance of virus specific stem-like CD8+ T cells that play a critical role in chronic viral infection. In particular, our study highlights the early generation of stem-like CD8+ T cells and their ability to adapt to either an acute or chronic infection. These findings are of broad significance since these novel stem-like CD8+ T cells play an important role in not only viral infections but also in cancer and autoimmunity.

Localized high-risk prostate cancer harbors an androgen receptor low subpopulation susceptible to HER2 inhibition

Patients diagnosed with localized high-risk prostate cancer have higher rates of recurrence, and the introduction of neoadjuvant intensive hormonal therapies seeks to treat occult micrometastatic disease by their addition to definitive treatment. Sufficient profiling of baseline disease has remained a challenge in enabling the in-depth assessment of phenotypes associated with exceptional vs. poor pathologic responses after treatment. In this study, we report comprehensive and integrative gene expression profiling of 37 locally advanced prostate tumors prior to six months of androgen deprivation therapy (ADT) plus the androgen receptor (AR) inhibitor enzalutamide prior to radical prostatectomy. A robust transcriptional program associated with HER2 activity was positively associated with poor outcome and opposed AR activity, even after adjusting for common genomic alterations in prostate cancer including PTEN loss and expression of the TMPRSS2:ERG fusion. Patients experiencing exceptional pathologic responses demonstrated lower levels of HER2 and phospho-HER2 by immunohistochemistry of biopsy tissues. The inverse correlation of AR and HER2 activity was found to be a universal feature of all aggressive prostate tumors, validated by transcriptional profiling an external cohort of 121 patients and immunostaining of tumors from 84 additional patients. Importantly, the AR activity-low, HER2 activity-high cells that resist ADT are a pre-existing subset of cells that can be targeted by HER2 inhibition alone or in combination with enzalutamide. In summary, we show that prostate tumors adopt an AR activity-low prior to antiandrogen exposure that can be exploited by treatment with HER2 inhibitors.

Characteristics and anatomic location of PD-1+TCF1+ stem-like CD8 T cells in chronic viral infection and cancer

CD8 T cells play an essential role in antitumor immunity and chronic viral infections. Recent findings have delineated the differentiation pathway of CD8 T cells in accordance with the progenitor-progeny relationship of TCF1+ stem-like and Tim-3+TCF1- more differentiated T cells. Here, we investigated the characteristics of stem-like and differentiated CD8 T cells isolated from several murine tumor models and human lung cancer samples in terms of phenotypic and transcriptional features as well as their location compared to virus-specific CD8 T cells in the chronically lymphocytic choriomeningitis virus (LCMV)-infected mice. We found that CD8 tumor-infiltrating lymphocytes (TILs) in both murine and human tumors exhibited overall similar phenotypic and transcriptional characteristics compared to corresponding subsets in the spleen of chronically infected mice. Moreover, stem-like CD8 TILs exclusively responded and produced effector-like progeny CD8 T cells in vivo after antigenic restimulation, confirming their lineage relationship and the proliferative potential of stem-like CD8 TILs. Most importantly, similar to the preferential localization of PD-1+ stem-like CD8 T cells in T cell zones of the spleen during chronic LCMV infection, we found that the PD-1+ stem-like CD8 TILs in lung cancer samples are preferentially located not in the tumor parenchyma but in tertiary lymphoid structures (TLSs). The stem-like CD8 T cells are present in TLSs located within and at the periphery of the tumor, as well as in TLSs closely adjacent to the tumor parenchyma. These findings suggest that TLSs provide a protective niche to support the quiescence and maintenance of stem-like CD8 T cells in the tumor.

Abstract B025: CD28-negative T cells from head and neck cancer patients are functionally frail but not senescent

Introduction: T cells lacking costimulatory receptors CD27/28, with high levels of differentiation markers CD57 and KLRG1, may accumulate with aging. These T cells have been described as “senescent” (unable to proliferate) with high cytolytic enzyme expression. However, robust functional studies on these cells are lacking. Further, emerging studies on the implications of these cells in the context of prognosis and responses to immunotherapy have shown mixed results. To better understand the role of these cells in the pathogenesis of cancer, a better understanding of their functional potential is needed. Methods and Results: We collected blood from 46 patients with previously untreated, locally advanced head and neck squamous cell carcinoma (HNSCC), aged 47-89, undergoing surgery. Matched tumor tissue was collected from 29 patients. Samples were analyzed by flow cytometry. There was correlation between the percentage of CD27/28-CD57+ (CD28neg) T cells in the blood vs. tumor (R2 = 0.51 for CD8+, 0.41 for CD4+; p<0.001). The CD28neg proportion among CD8+ T cells was significantly higher in patients aged 70 or greater vs. patients under age 70. CD28neg cells from blood and tumors expressed very high levels of granzyme B and perforin but were not enriched for senescence markers p16 and beta-galactosidase. Additional CD8+ cells from the peripheral blood were sorted into CD28neg (CD27/28-CD57+) vs. CD27/28+ for comparative functional studies. Proliferation assays showed a stepwise reduction in CellTrace Violet in both the CD28neg and CD27/28+ populations over 5 days in culture with IL-2 and CD2/3/28 stimulation cocktail. While the percentage of CD28neg cells that had completed 3 or more cell divisions was significantly reduced from that of the CD27/28+ population, approximately 40% of the CD28neg cells had divided at least three times over 5 days in culture. Sorted CD28neg cells retained high levels of granzyme B/perforin, and PMA/ionomycin stimulation induced increased CD107a expression and granzyme B secretion, suggesting that these cells do possess enhanced cytolytic capacity. CD28neg cells also expressed higher levels of surface phosphatidylserine, which has been associated with cellular stress in viable cells. CD28neg cells stimulated with CD3 beads secreted higher levels of TNF-a, but not IFN-g or IL-2, vs. CD27/28+ cells. Conclusions: CD28neg T cells sampled from HNSCC patients have altered functionality, including a reduced (but intact) capacity to proliferate and increased phosphatidylserine expression. However, they also have enhanced capacity to secrete cytolytic enzymes and TNF-a, suggesting they may have differentiated to perform those specific functions. We propose that these T cells are more appropriately described as “frail,” and “immunofrailty” may be a more appropriate term than “immunosenescence.” Additional prospective clinical studies are needed to elucidate the effects of these cells on prognosis and treatment responses in cancer patients.

Citation Format: Brendan L.C. Kinney, Connor Parrish, Vikash Kansal, Zachary S. Buchwald, Haydn T. Kissick, Amy Y. Chen, Nicole C. Schmitt. CD28-negative T cells from head and neck cancer patients are functionally frail but not senescent [abstract]. In: Proceedings of the AACR Special Conference: Aging and Cancer; 2022 Nov 17-20; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2022;83(2 Suppl_1):Abstract nr B025.

Invariant NKT cell-augmented GM-CSF-secreting tumor vaccine is effective in advanced prostate cancer model

Invariant natural killer T cells (iNKT cells) express a semi-invariant T cell receptor that recognizes certain glycolipids (including α-galactosylceramide, αGC) bound to CD1d, and can induce potent antitumor responses. Here, we assessed whether αGC could enhance the efficacy of a GM-CSF-producing tumor cell vaccine in the transgenic SV40 T antigen-driven TRAMP prostate cancer model. In healthy mice, we initially found that optimal T cell responses were obtained with αGC-pulsed TRAMP-C2 cells secreting GM-CSF and milk fat globule epidermal growth factor protein-8 (MFG-E8) with an RGD to RGE mutation (GM-CSF/RGE TRAMP-C2), combined with systemic low dose IL-12. In a therapeutic model, transgenic TRAMP mice were then castrated at ~ 20 weeks, followed by treatment with the combination vaccine. Untreated mice succumbed to tumor by ~ 40 weeks, but survival was markedly prolonged by vaccine treatment, with most mice surviving past 80 weeks. Prostates in the treated mice were heavily infiltrated with T cells and iNKT cells, which both secreted IFNγ in response to tumor cells. The vaccine was not effective if the αGC, IL-12, or GM-CSF secretion was eliminated. Finally, immunized mice were fully resistant to challenge with TRAMP-C2 cells. Together these findings support further development of therapeutic vaccines that exploit iNKT cell activation.

PD-1 combination therapy with IL-2 modifies CD8+ T cell exhaustion program

Combination therapy with PD-1 blockade and IL-2 is highly effective during chronic lymphocytic choriomeningitis virus infection1. Here we examine the underlying basis for this synergy. We show that PD-1 + IL-2 combination therapy, in contrast to PD-1 monotherapy, substantially changes the differentiation program of the PD-1+TCF1+ stem-like CD8+ T cells and results in the generation of transcriptionally and epigenetically distinct effector CD8+ T cells that resemble highly functional effector CD8+ T cells seen after an acute viral infection. The generation of these qualitatively superior CD8+ T cells that mediate viral control underlies the synergy between PD-1 and IL-2. Our results show that the PD-1+TCF1+ stem-like CD8+ T cells, also referred to as precursors of exhausted CD8+ T cells, are not fate-locked into the exhaustion program and their differentiation trajectory can be changed by IL-2 signals. These virus-specific effector CD8+ T cells emerging from the stem-like CD8+ T cells after combination therapy expressed increased levels of the high-affinity IL-2 trimeric (CD25-CD122-CD132) receptor. This was not seen after PD-1 blockade alone. Finally, we show that CD25 engagement with IL-2 has an important role in the observed synergy between IL-2 cytokine and PD-1 blockade. Either blocking CD25 with an antibody or using a mutated version of IL-2 that does not bind to CD25 but still binds to CD122 and CD132 almost completely abrogated the synergistic effects observed after PD-1 + IL-2 combination therapy. There is considerable interest in PD-1 + IL-2 combination therapy for patients with cancer2,3, and our fundamental studies defining the underlying mechanisms of how IL-2 synergizes with PD-1 blockade should inform these human translational studies.

TGF-β regulates the stem-like state of PD-1+ TCF-1+ virus-specific CD8 T cells during chronic infection

Recent studies have defined a novel population of PD-1+ TCF-1+ stem-like CD8 T cells in chronic infections and cancer. These quiescent cells reside in lymphoid tissues, are critical for maintaining the CD8 T cell response under conditions of persistent antigen, and provide the proliferative burst after PD-1 blockade. Here we examined the role of TGF-β in regulating the differentiation of virus-specific CD8 T cells during chronic LCMV infection of mice. We found that TGF-β signaling was not essential for the generation of the stem-like CD8 T cells but was critical for maintaining the stem-like state and quiescence of these cells. TGF-β regulated the unique transcriptional program of the stem-like subset, including upregulation of inhibitory receptors specifically expressed on these cells. TGF-β also promoted the terminal differentiation of exhausted CD8 T cells by suppressing the effector-associated program. Together, the absence of TGF-β signaling resulted in significantly increased accumulation of effector-like CD8 T cells. These findings have implications for immunotherapies in general and especially for T cell therapy against chronic infections and cancer.

Sarcopenia and systemic inflammation are associated with decreased survival after cytoreductive nephrectomy for metastatic renal cell carcinoma

BACKGROUND

This study was aimed at assessing the associations of sarcopenia, muscle density, adiposity, and inflammation with overall survival (OS) after cytoreductive nephrectomy (CN) for metastatic renal cell carcinoma.

METHODS

In all, 158 patients undergoing CN from 2001 to 2014 had digitized preoperative imaging for tissue segmentation via Slice-O-Matic software (version 5.0) at the mid-L3 level. The skeletal muscle index was calculated with the skeletal muscle area (cm² ) normalized for height (m² ), and the skeletal muscle density (SMD) was calculated with average Hounsfield units. Adiposity was measured with the cross-sectional area (cm² ) of visceral, subcutaneous, and intramuscular adiposity compartments and was similarly normalized for height. The average fat density was obtained in Hounsfield units. OS was estimated with the Kaplan-Meier method. Associations between body composition, inflammation metrics, and relevant clinicopathology and OS were assessed with univariable and multivariate Cox analyses.

RESULTS

Seventy-six of the 158 patients (48%) were sarcopenic. Sarcopenia was associated with elevated neutrophil to lymphocyte ratios (NLRs; P = .02), increased age (P = .001), lower body mass indices (P = .009), greater modified Motzer scores (P = .019), and lower SMD (P = .006). The median OS was 15.0 and 29.4 months for sarcopenic and nonsarcopenic patients, respectively (P = .04). Elevated inflammation (NLR or C-reactive protein), in addition to sarcopenia, was independently associated with OS, with an elevated NLR ≥ 3.5 and sarcopenia associated with the poorest OS at 10.2 months. No associations were observed between measurements of muscle density or adiposity and OS.

CONCLUSIONS

Sarcopenia and measures of high systemic inflammation are additively associated with inferior OS after CN and may be of use in preoperative risk stratification.

LAY SUMMARY

Body composition and sarcopenia (a deficiency in skeletal musculature) have been shown to affect outcomes in cancer. We found that sarcopenic patients had poor survival in comparison with nonsarcopenic patients in the setting of metastatic renal cell carcinoma (mRCC). Patients with both elevated inflammation and sarcopenia had the poorest survival. Sarcopenia is an objective measure of nutrition that can assist in therapeutic counseling and decision-making for individualized treatment in mRCC.

Defining the Molecular Hallmarks of T-Cell Memory

The pool of memory CD8 T cells is comprised of highly specialized subpopulations of cells with both shared and distinct functions. The ongoing study of T-cell memory is focused on how these different subpopulations arise, how the cells are maintained over the life of the host, and how the cells protect a host against reinfection. As a field we have used the convenience of a narrow range of surface markers to define and study these memory T-cell subsets. However, as we learn more about these cells, it is becoming clear that these broad definitions are insufficient to capture the complexity of the CD8 memory T-cell pool, and an updated definition of these cellular states are needed. Here, we discuss data that have recently arisen that highlight the difficulty in using surface markers to functionally characterize CD8 T-cell populations, and the possibility of using the epigenetic state of cells to more clearly define the functional capacity of CD8 memory T-cell subsets.

Case Report: Exceptional Response to Nivolumab Plus Ipilimumab in a Young Woman With TFE3-SFPQ Fusion Translocation-Associated Renal Cell Carcinoma

Translocation-associated renal cell carcinoma (tRCC) is a rare, aggressive malignancy that primarily affects children and young adults. There is no clear consensus on the most effective treatment for tRCC and there are no biomarkers of response to treatments in these patients. We present a case of a 23 year-old female with metastatic tRCC to the lungs who was started on treatment with nivolumab and ipilimumab. She had a complete radiographic response to treatment and has been progression-free for over 18 months. Immunofluorescence imaging performed on the baseline primary tumor sample showed significant intratumoral immune infiltration. Importantly, these cells are present in niches characterized by TCF1+ CD8+ T cells. Histopathologic investigation showed the presence of lymphocytes in the fibrovascular septae and foci of lymphovascular invasion. Furthermore, lymphovascular invasion and intratumor niches with TCF1+ CD8+ T cells may predict a favorable response to treatment with nivolumab and ipilimumab. These findings have significant clinical relevance given that immune checkpoint inhibitors are approved for several malignancies and predictive biomarkers for response to treatment are lacking. Importantly, the identification of these TCF1+ CD8+ T cells may guide treatment for patients with tRCC, which is a rare malignancy without a consensus first-line treatment option.

Defining HPV-specific B cell responses in patients with head and neck cancer

Tumours often contain B cells and plasma cells but the antigen specificity of these intratumoral B cells is not well understood^1-8. Here we show that human papillomavirus (HPV)-specific B cell responses are detectable in samples from patients with HPV-positive head and neck cancers, with active production of HPV-specific IgG antibodies in situ. HPV-specific antibody secreting cells (ASCs) were present in the tumour microenvironment, with minimal bystander recruitment of influenza-specific cells, suggesting a localized and antigen-specific ASC response. HPV-specific ASC responses correlated with titres of plasma IgG and were directed against the HPV proteins E2, E6 and E7, with the most dominant response against E2. Using intratumoral B cells and plasma cells, we generated several HPV-specific human monoclonal antibodies, which exhibited a high degree of somatic hypermutation, consistent with chronic antigen exposure. Single-cell RNA sequencing analyses detected activated B cells, germinal centre B cells and ASCs within the tumour microenvironment. Compared with the tumour parenchyma, B cells and ASCs were preferentially localized in the tumour stroma, with well-formed clusters of activated B cells indicating ongoing germinal centre reactions. Overall, we show that antigen-specific activated and germinal centre B cells as well as plasma cells can be found in the tumour microenvironment. Our findings provide a better understanding of humoral immune responses in human cancer and suggest that tumour-infiltrating B cells could be harnessed for the development of therapeutic agents.

Body Composition as an Independent Predictive and Prognostic Biomarker in Advanced Urothelial Carcinoma Patients Treated with Immune Checkpoint Inhibitors

BACKGROUND

Several immune checkpoint inhibitors (ICIs) are approved for the treatment of advanced urothelial carcinoma (UC). There are limited biomarkers for ICI-treated patients with UC. We investigated the association between body composition and clinical outcomes in ICI-treated UC patients.

MATERIALS AND METHODS

We conducted a retrospective analysis of 70 ICI-treated patients with advanced UC at Winship Cancer Institute from 2015 to 2020. Baseline computed tomography images within 2 months of ICI initiation were collected at mid-L3 and muscle and fat compartments (subcutaneous, intermuscular, and visceral) were segmented using SliceOMatic v5.0 (TomoVision, Magog, Canada). A prognostic body composition risk score (high: 0-1, intermediate: 2-3, or low-risk: 4) was created based on the β coefficient from the multivariate Cox model (MVA) following best-subset variable selection. Our body composition risk score was skeletal muscle index (SMI) + 2 × attenuated skeletal muscle (SM) mean + visceral fat index (VFI). Concordance statistics (C-statistics) were used to quantify the discriminatory magnitude of the predictive model.

RESULTS

Most patients (70%) were men and the majority received ICIs in the second- (46%) or third-line (21%) setting. High-risk patients had significantly shorter overall survival (OS; hazard ratio [HR], 6.72; p < .001), progression-free survival (HR, 5.82; p < .001), and lower chance of clinical benefit (odds ratio [OR], 0.02; p = .003) compared with the low-risk group in MVA. The C-statistics for our body composition risk group and myosteatosis analyses were higher than body mass index for all clinical outcomes.

CONCLUSION

Body composition variables such as SMI, SM mean, and VFI may be prognostic and predictive of clinical outcomes in ICI-treated patients with UC. Larger, prospective studies are warranted to validate this hypothesis-generating data.

IMPLICATIONS FOR PRACTICE

This study developed a prognostic body composition risk scoring system using radiographic biomarkers for patients with bladder cancer treated with immunotherapy. The study found that the high-risk patients had significantly worse clinical outcomes. Notably, the study's model was better at predicting outcomes than body mass index. Importantly, these results suggest that radiographic measures of body composition should be considered for inclusion in updated prognostic models for patients with urothelial carcinoma treated with immunotherapy. These findings are useful for practicing oncologists in the academic or community setting, particularly given that baseline imaging is routine for patients starting on treatment with immunotherapy.

Body Composition Variables as Radiographic Biomarkers of Clinical Outcomes in Metastatic Renal Cell Carcinoma Patients Receiving Immune Checkpoint Inhibitors

BACKGROUND

Immune checkpoint inhibitors (ICI) have revolutionized the treatment of metastatic renal cell carcinoma (mRCC). Biomarkers for mRCC patients treated with ICI are limited, and body composition is underutilized in mRCC. We investigated the association between body composition and clinical outcomes in ICI-treated mRCC patients.

METHODS

We performed a retrospective analysis of 79 ICI-treated mRCC patients at Winship Cancer Institute from 2015-2020. Baseline CT images were collected at mid-L3 and segmented using SliceOMatic v5.0 (TomoVision). Density of skeletal muscle (SM), subcutaneous fat, inter-muscular fat, and visceral fat were measured and converted to indices by dividing by height(m)2 (SMI, SFI, IFI, and VFI, respectively). Total fat index (TFI) was defined as the sum of SFI, IFI, and VFI. Patients were characterized as high versus low for each variable at gender-specific optimal cuts using overall survival (OS) as the primary outcome. A prognostic risk score was created based on the beta coefficient from the multivariable Cox model after best subset variable selection. Body composition risk score was calculated as IFI + 2*SM mean + SFI and patients were classified as poor (0-1), intermediate (2), or favorable risk (3-4). Kaplan-Meier method and Log-rank test were used to estimate OS and PFS and compare the risk groups. Concordance statistics (C-statistics) were used to measure the discriminatory magnitude of the model.

RESULTS

Most patients were male (73%) and most received ICI as first (35%) or second-line (51%) therapy. The body composition poor-risk patients had significantly shorter OS (HR: 6.37, p<0.001), PFS (HR: 4.19, p<0.001), and lower chance of CB (OR: 0.23, p=0.044) compared to favorable risk patients in multivariable analysis. Patients with low TFI had significantly shorter OS (HR: 2.72, p=0.002), PFS (HR: 1.91, p=0.025), and lower chance of CB (OR: 0.25, p=0.008) compared to high TFI patients in multivariable analysis. The C-statistics were higher for body composition risk groups and TFI (all C-statistics ≥ 0.598) compared to IMDC and BMI.

CONCLUSIONS

Risk stratification using the body composition variables IFI, SM mean, SFI, and TFI may be prognostic and predictive of clinical outcomes in mRCC patients treated with ICI. Larger, prospective studies are warranted to validate this hypothesis-generating data.

Blockade of immune checkpoints in lymph nodes through locoregional delivery augments cancer immunotherapy

Systemic administration of immune checkpoint blockade (ICB) monoclonal antibodies (mAbs) can unleash antitumor functions of T cells but is associated with variable response rates and off-target toxicities. We hypothesized that antitumor efficacy of ICB is limited by the minimal accumulation of mAb within tissues where antitumor immunity is elicited and regulated, which include the tumor microenvironment (TME) and secondary lymphoid tissues. In contrast to systemic administration, intratumoral and intradermal routes of administration resulted in higher mAb accumulation within both the TME and its draining lymph nodes (LNs) or LNs alone, respectively. The use of either locoregional administration route resulted in pronounced T cell responses from the ICB therapy, which developed in the secondary lymphoid tissues and TME of treated mice. Targeted delivery of mAb to tumor-draining lymph nodes (TdLNs) alone was associated with enhanced antitumor immunity and improved therapeutic effects compared to conventional systemic ICB therapy, and these effects were sustained at reduced mAb doses and comparable to those achieved by intratumoral administration. These data suggest that locoregional routes of administration of ICB mAb can augment ICB therapy by improving immunomodulation within TdLNs.

Immune-Related Adverse Events as Clinical Biomarkers in Patients with Metastatic Renal Cell Carcinoma Treated with Immune Checkpoint Inhibitors

BACKGROUND

Immune checkpoint inhibitors (ICIs) are an important treatment for metastatic renal cell carcinoma (mRCC). These agents may cause immune-related adverse events (irAEs), and the relationship between irAEs and outcomes is poorly understood. We investigated the association between irAEs and clinical outcomes in patients with mRCC treated with ICIs.

METHODS

We performed a retrospective study of 200 patients with mRCC treated with ICIs at Winship Cancer Institute from 2015 to 2020. Data on irAEs were collected from clinic notes and laboratory values and grades were determined using Common Terminology Criteria in Adverse Events version 5.0. The association with overall survival (OS) and progression-free survival (PFS) was modeled by Cox proportional hazards model. Logistic regression models were used to define odds ratios (ORs) for clinical benefit (CB). Landmark analysis and extended Cox models were used to mitigate lead-time bias by treating irAEs as a time-varying covariate.

RESULTS

Most patients (71.0%) were male, and one-third of patients (33.0%) experienced at least one irAE, most commonly involving the endocrine glands (13.0%), gastrointestinal tract (10.5%), or skin (10.0%). Patients who experienced irAEs had significantly longer OS (hazard ratio [HR], 0.52; p = .013), higher chance of CB (OR, 2.10; p = .023) and showed a trend toward longer PFS (HR, 0.71; p = .065) in multivariate analysis. Patients who had endocrine irAEs, particularly thyroid irAEs, had significantly longer OS and PFS and higher chance of CB. In a 14-week landmark analysis, irAEs were significantly associated with prolonged OS (p = .045). Patients who experienced irAEs had significantly longer median OS (44.5 vs. 18.2 months, p = .005) and PFS (7.5 vs. 3.6 months, p = .003) without landmark compared with patients who did not.

CONCLUSION

We found that patients with mRCC treated with ICIs who experienced irAEs, particularly thyroid irAEs, had significantly improved clinical outcomes compared with patients who did not have irAEs. This suggests that irAEs may be effective clinical biomarkers in patients with mRCC treated with ICIs. Future prospective studies are warranted to validate these findings.

IMPLICATIONS FOR PRACTICE

This study found that early onset immune-related adverse events (irAEs) are associated with significantly improved clinical outcomes in patients with metastatic renal cell carcinoma (mRCC) treated with immune checkpoint inhibitors (ICIs). In this site-specific irAE analysis, endocrine irAEs, particularly thyroid irAEs, were significantly associated with improved clinical outcomes. These results have implications for practicing medical oncologists given the increasing use of ICIs for the treatment of mRCC. Importantly, these results suggest that early irAEs and thyroid irAEs at any time on treatment with ICIs may be clinical biomarkers of clinical outcomes in patients with mRCC treated with ICIs.

Abstract PO-041: An immunologic niche of antigen presenting cells and stem-like CD8+ T-cells is present in non-small cell lung cancer brain metastases

Background: Non-small cell lung cancer (NSCLC) patients with brain metastases have a very poor prognosis. The first line treatments for NSCLC brain metastases are typically surgery and pre- or post-operative stereotactic radiosurgery (SRS) or SRS alone. However, subsequent intra-cranial failure and death is common. Importantly, we have previously shown that a unique immune niche in genitourinary malignancies correlates with the risk for disease recurrence. Accordingly, here we investigated whether this immune niche was present in brain metastases, whether it correlated with patient outcomes, and whether it was modulated by SRS. Methods: Formalin fixed paraffin embedded brain metastases were stained by immunofluorescence for CD8, PD-1, TCF-1, MHC-II and DAPI. Following successful image acquisition using fluorescent whole slide scanning, we used a custom quantitative analysis pipeline to measure the cellularity, relative cellular locations, local cellular density, and marker staining intensity. Results: We identified immune niches consisting of both stem-like TCF-1+ CD8+ T-cells and antigen presenting cells (MHC-II+) in brain metastases. TCF-1+ CD8+ T-cells were found at in areas of higher MHC-II+ cell density than the TCF-1 CD8+negative T-cells. The amount of tumor issue occupied by immune niches correlated with TCF1+ CD8+ T-cell infiltration, as well as with total CD8+ T-cell and MHC-II+ cell infiltration. Importantly, we found that higher MHC-II+ cell density correlated with longer overall survival in this cohort of patients. Additionally, we found this immune niche is preserved following pre-operative SRS. Conclusions: Our study is the first to demonstrate stem-like CD8+ T-cells in brain metastases and that these cells form an immune niche similar to those described extra-cranial tumor sites. Additionally, we report that the immune niche is preserved following SRS, which is highly clinically relevant to the use of combinatorial strategies between SRS and checkpoint blockade.

Citation Format: Caroline S. Jansen, Luke del Balzo, Roshan Prabhu, Suzanna Logan, Prasanthi Chappa, Kirtesh Patel, Scott Wilkinson, Ross Lake, Hui-Kuo G. Shu, Jim Zhong, Vishal Dhere, Jeffrey Olson, Adam G. Sowalsky, Mohammad K. Khan, Haydn T. Kissick, Zachary S. Buchwald. An immunologic niche of antigen presenting cells and stem-like CD8+ T-cells is present in non-small cell lung cancer brain metastases [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PO-041.

CMV Status Drives Distinct Trajectories of CD4+ T Cell Differentiation

Cytomegalovirus (CMV) is one of the most commonly recognized opportunistic pathogens and remains the most influential known parameter in shaping an individual's immune system. As such, T cells induced by CMV infection could have a long-term impact on subsequent immune responses. Accumulating evidence indicates that memory T cells developed during past bacterial and viral infection can cross-react with unrelated pathogens, including transplant antigens, and can alter responses to de novo infections, vaccines, cancers, or rejection. Therefore, careful examination of T cell responses elicited by CMV is warranted to understand their potentially beneficial or harmful roles in future major immune events. Our detailed exploration of the distribution, phenotype, TCR repertoire and transcriptome of CD4+ T cells within CMV seropositive healthy individuals using high-dimensional flow cytometry and single cell multi-omics sequencing reveals that CMV seropositivity has highly significant age-independent effects, leading to a reduction in CD4+ naïve T cells and an expansion of CD4+ effector memory T cells and CD45RA+ effector memory T cells. These induced CD4+ effector memory T cells undergo a specific differentiation trajectory resulting in a subpopulation of CD57+CD27-CD28-CD244+ CD4+ T cells with cytotoxic function and TCR oligoclonality for optimal controlled coexistence with cytomegalovirus. Through gene set enrichment analysis, we found that this subpopulation is similar to virus-specific CD8+ T cells and T cells that mediate acute rejection in patients using tacrolimus and belatacept, a selective costimulation blocker. Together, these data suggest that memory CD4+ T cells induced by cytomegalovirus are formed via a distinct differentiation program to acquire cytotoxic function and can be potentially detrimental to transplant patients adopting costimulation blockade immunosuppressive regimen.

Quality of CD8+ T cell immunity evoked in lymph nodes is compartmentalized by route of antigen transport and functional in tumor context

Revealing the mechanisms that underlie the expansion of antitumor CD8+ T cells that are associated with improved clinical outcomes is critical to improving immunotherapeutic management of melanoma. How the lymphatic system, which orchestrates the complex sensing of antigen by lymphocytes to mount an adaptive immune response, facilitates this response in the context of malignancy is incompletely understood. To delineate the effects of lymphatic transport and tumor-induced lymphatic and lymph node (LN) remodeling on the elicitation of CD8+ T cell immunity within LNs, we designed a suite of nanoscale biomaterial tools enabling the quantification of antigen access and presentation within the LN and resulting influence on T cell functions. The expansion of antigen-specific stem-like and cytotoxic CD8+ T cell pools was revealed to be sensitive to the mechanism of lymphatic transport to LNs, demonstrating the potential for nanoengineering strategies targeting LNs to optimize cancer immunotherapy in eliciting antitumor CD8+ T cell immunity.

Organized immune cell interactions within tumors sustain a productive T-cell response

Tumor-infiltrating CD8 T cells are associated with improved patient survival and response to immunotherapy in various cancers. Persistent antigen leads to CD8 T-cell exhaustion, where proliferation/self-renewal and killing are divided within distinct subsets of CD8 T cells in the tumor. CD8 T-cell responses in chronic antigen settings must be maintained for long periods of time, suggesting that mechanisms that regulate chronic CD8 T-cell responses may differ from those in acute settings. Currently, factors that regulate the maintenance of stem-like CD8 T cells in the tumor or their differentiation into terminally differentiated cells are unknown. In this review, we discuss the role of dendritic cells in the activation and differentiation of CD8 T-cell subsets within secondary lymphoid tissue and tumors. In addition, we examine changes in CD4 T-cell differentiation in response to chronic antigens and consider how subset-specific mechanisms could assist the stem-like and terminally differentiated CD8 T-cell subsets. Finally, we highlight how tumor-infiltrating CD4 T cells and dendritic cells interact with CD8 T cells within organized lymphoid-like areas in the tumor and propose a CD8 T-cell differentiation model that requires the collaboration of CD4 T cells and dendritic cells. These organized interactions coordinate the anti-tumor response and control disease progression by mechanisms that regulate CD8 T-cell differentiation, which permit the maintenance of an effective balance of stem-like and terminally differentiated CD8 T cells.

Novel Risk Scoring System for Patients with Metastatic Renal Cell Carcinoma Treated with Immune Checkpoint Inhibitors

BACKGROUND

The International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) criteria are the gold standard for risk-stratifying patients with metastatic renal cell cancer (mRCC). We developed a novel risk scoring system for patients with mRCC treated with immune checkpoint inhibitors (ICIs).

METHODS

We performed a retrospective analysis of 100 ICI-treated patients with mRCC at Winship Cancer Institute from 2015 to 2018. Several baseline variables were collected, including markers of inflammation, body mass index (BMI), and sites of metastatic disease, and all were considered for inclusion in our risk scoring system. Upon variable selection in multivariable model, monocyte-to-lymphocyte ratio (MLR), BMI, and number and sites of metastases at baseline were used for risk score calculation. Patients were categorized using four-level risk groups as good (risk score = 0), intermediate (risk score = 1), poor (risk score = 2), or very poor (risk score = 3-4). Cox's proportional hazard model and the Kaplan-Meier method were implemented for survival outcomes.

RESULTS

Most patients were male (66%) with clear cell renal cell carcinoma (72%). The majority (71%) received anti-programmed cell death protein-1 monotherapy. Our risk scoring criteria had higher Uno's concordance statistics than IMDC in predicting overall survival (OS; 0.71 vs. 0.57) and progression-free survival (0.61 vs. 0.58). Setting good risk (MLR <0.93, BMI ≥24, and D_Met = 0) as the reference, the OS hazard ratios were 29.5 (95% confidence interval [CI], 3.64-238.9), 6.58 (95% CI, 0.84-51.68), and 3.75 (95% CI, 0.49-28.57) for very poor, poor, and intermediate risk groups, respectively.

CONCLUSION

Risk scoring using MLR, BMI, and number and sites of metastases may be an effective way to predict survival in patients with mRCC receiving ICI. These results should be validated in a larger, prospective study.

IMPLICATIONS FOR PRACTICE

A risk scoring system was created for patients with metastatic renal cell carcinoma treated with immune checkpoint inhibitors. The results of this study have significant implications for practicing oncologists in the community and academic setting. Importantly, these results identify readily available risk factors that can be used clinically to risk-stratify patients with metastatic renal cell carcinoma who are treated with immune checkpoint inhibitors.

Immunological Complexity of the Prostate Cancer Microenvironment Influences the Response to Immunotherapy

Prostate cancer is one of the most common cancers in men and a leading cause of cancer-related death. Recent advances in the treatment of advanced prostate cancer, including the use of more potent and selective inhibitors of the androgen signaling pathway, have provided significant clinical benefit for men with metastatic castration-resistant prostate cancer (mCRPC). However, most patients develop progressive lethal disease, highlighting the need for more effective treatments. One such approach is immunotherapy, which harness the power of the patient's immune system to identify and destroy cancer cells through the activation of cytotoxic CD8 T cells specific for tumor antigens. Although immunotherapy, particularly checkpoint blockade, can induce significant clinical responses in patients with solid tumors or hematological malignancies, minimal efficacy has been observed in men with mCRPC. In the current review, we discuss our current understanding of the immunological complexity of the immunosuppressive prostate cancer microenvironment, preclinical models of prostate cancer, and recent advances in immunotherapy clinical trials to improve outcomes for men with mCRPC.

Proliferating Transitory T Cells with an Effector-like Transcriptional Signature Emerge from PD-1+ Stem-like CD8+ T Cells during Chronic Infection

T cell dysfunction is a characteristic feature of chronic viral infection and cancer. Recent studies in chronic lymphocytic choriomeningitis virus (LCMV) infection have defined a PD-1+ Tcf-1+ CD8+ T cell subset capable of self-renewal and differentiation into more terminally differentiated cells that downregulate Tcf-1 and express additional inhibitory molecules such as Tim3. Here, we demonstrated that expression of the glycoprotein CD101 divides this terminally differentiated population into two subsets. Stem-like Tcf-1+ CD8+ T cells initially differentiated into a transitory population of CD101-Tim3+ cells that later converted into CD101+ Tim3+ cells. Recently generated CD101-Tim3+ cells proliferated in vivo, contributed to viral control, and were marked by an effector-like transcriptional signature including expression of the chemokine receptor CX3CR1, pro-inflammatory cytokines, and granzyme B. PD-1 pathway blockade increased the numbers of CD101-Tim3+ CD8+ T cells, suggesting that these newly generated transitional cells play a critical role in PD-1-based immunotherapy.

Combined Effect of Sarcopenia and Systemic Inflammation on Survival in Patients with Advanced Stage Cancer Treated with Immunotherapy

Background

Sarcopenia and inflammation have been associated with poor survival in patients with cancer. We explored the combined effects of these variables on survival in patients with cancer treated with immunotherapy.

Methods

We performed a retrospective review of 90 patients enrolled on immunotherapy‐based phase I clinical trials at Emory University from 2009 to 2017. Baseline neutrophil‐to‐lymphocyte ratio, monocyte‐to‐lymphocyte ratio, and platelet‐to‐lymphocyte ratio (PLR) were used as surrogates of inflammation. The skeletal muscle index (SMI) was derived from the skeletal muscle density calculated from baseline abdominal computed tomography images. Optimal cutoffs for continuous inflammation biomarkers and SMI were determined by bias‐adjusted log‐rank test. A four‐level risk stratification was used to create low‐risk (PLR <242 and nonsarcopenic), intermediate‐risk (PLR <242 and sarcopenic), high‐risk (PLR ≥242 and nonsarcopenic), and very‐high‐risk (PLR ≥242 and sarcopenic) groups with subsequent association with survival.

Results

Most patients (59%) were male, and the most common cancers were melanoma (33%) and gastrointestinal (22%). Very high‐risk, high‐risk, and intermediate‐risk patients had significantly shorter overall survival (hazard ratio [HR], 8.46; 95% confidence interval [CI], 2.65–27.01; p < .001; HR, 5.32; CI, 1.96–14.43; p = .001; and HR, 4.01; CI, 1.66–9.68; p = .002, respectively) and progression‐free survival (HR, 12.29; CI, 5.15–29.32; p < .001; HR, 3.51; CI, 1.37–9.02; p = .009; and HR, 2.14; CI, 1.12–4.10; p = .022, respectively) compared with low‐risk patients.

Conclusion

Baseline sarcopenia and elevated inflammatory biomarkers may have a combined effect on decreasing survival in immunotherapy‐treated patients in phase I trials. These data may be immediately applicable for medical oncologists for the risk stratification of patients beginning immunotherapeutic agents.

Implications for Practice

Sarcopenia and inflammation have been associated with poor survival in patients with cancer, but it is unclear how to apply this information to patient care. The authors created a risk‐stratification system that combined sarcopenia and platelet‐to‐lymphocyte ratio as a marker of systemic inflammation. The presence of sarcopenia and systemic inflammation decreased progression‐free survival and overall survival in our cohort of 90 patients who received immunotherapy in phase I clinical trials. The data presented in this study may be immediately applicable for medical oncologists as a way to risk‐stratify patients who are beginning treatment with immunotherapy.

The interaction between chronic inflammation and body composition is particularly important in the era of immunotherapy, considering that immune checkpoint inhibitors rely on the host immune system for their efficacy. This article reports on the combined effects of inflammation and sarcopenia on clinical outcomes in patients with solid tumors treated with immunotherapy‐based regimens.

Phosphoinositide 3-Kinase Signaling Can Modulate MHC Class I and II Expression

Molecular events activating the PI3K pathway are frequently detected in human tumors and the activation of PI3K signaling alters numerous cellular processes including tumor cell proliferation, survival, and motility. More recent studies have highlighted the impact of PI3K signaling on the cellular response to interferons and other immunologic processes relevant to antitumor immunity. Given the ability of IFNγ to regulate antigen processing and presentation and the pivotal role of MHC class I (MHCI) and II (MHCII) expression in T-cell-mediated antitumor immunity, we sought to determine the impact of PI3K signaling on MHCI and MHCII induction by IFNγ. We found that the induction of cell surface MHCI and MHCII molecules by IFNγ is enhanced by the clinical grade PI3K inhibitors dactolisib and pictilisib. We also found that PI3K inhibition increases STAT1 protein levels following IFNγ treatment and increases accessibility at genomic STAT1-binding motifs. Conversely, we found that pharmacologic activation of PI3K signaling can repress the induction of MHCI and MHCII molecules by IFNγ, and likewise, the loss of PTEN attenuates the induction of MHCI, MHCII, and STAT1 by IFNγ. Consistent with these in vitro studies, we found that within human head and neck squamous cell carcinomas, intratumoral regions with high phospho-AKT IHC staining had reduced MHCI IHC staining. IMPLICATIONS: Collectively, these findings demonstrate that MHC expression can be modulated by PI3K signaling and suggest that activation of PI3K signaling may promote immune escape via effects on antigen presentation.

CD8 T Cell Exhaustion in Chronic Infection and Cancer: Opportunities for Interventions

Antigen-specific CD8 T cells are central to the control of chronic infections and cancer, but persistent antigen stimulation results in T cell exhaustion. Exhausted CD8 T cells have decreased effector function and proliferative capacity, partly caused by overexpression of inhibitory receptors such as programmed cell death (PD)-1. Blockade of the PD-1 pathway has opened a new therapeutic avenue for reinvigorating T cell responses, with positive outcomes especially for patients with cancer. Other strategies to restore function in exhausted CD8 T cells are currently under evaluation-many in combination with PD-1-targeted therapy. Exhausted CD8 T cells comprise heterogeneous cell populations with unique differentiation and functional states. A subset of stem cell-like PD-1⁺ CD8 T cells responsible for the proliferative burst after PD-1 therapy has been recently described. A greater understanding of T cell exhaustion is imperative to establish rational immunotherapeutic interventions.

Abstract 2700: CD8 T-cell infiltration into renal tumors requires a supportive antigen-presenting niche

Background: Tumor infiltrating immune cells have a clear prognostic benefit in many tumor types. Immune variables have independently improved prognostication in various cancer types, with tumor-infiltrating lymphocytes (TILs) more accurately predicting patient survival than currently employed methods. This has been shown using the Immuno-score, which predicts disease progression in colorectal cancer based on CD8 T cell infiltration. Many recent studies have also highlighted similar observations in other cancers, including breast cancer, lung cancer, and melanoma. These observations raise the question of whether the level of CD8 T cell infiltration into renal cell tumors may also predict patient survival, and more fundamentally, why some patients may mount a strong immune response to their tumors and others do not.

Methods: Tumor tissue was collected from 68 renal cell carcinoma (RCC) patients undergoing surgery at Emory University Hospital. Patients had a minimum follow up time of 24 months. Intraoperative tumor samples were processed and analyzed by flow cytometry and immunofluorescence.

Results: The proportion of CD8 TILs, measured by flow cytometry, was found to vary widely in RCC patients. This CD8 T cell response is independent of standard risk assessment tools, tumor size, pathology, and patient demographics. Significantly, an increasing percent of tumor CD8 T cells is associated with improved cancer-specific survival in these patients, and this association is particularly strong in a small cohort of stage III patients.

The phenotype and functional capacity of TILs were examined, and presence of a stem-like CD8 T cell—that can proliferate and differentiate—was required to generate a strong anti-tumor Tcell response. When this stem-like T cell is lost, there is a poor anti-tumor immune response and patients experience progressive disease. Flow cytometry analysis revealed that the number of dendritic cells in the tumor correlates with T cell infiltration, and immunofluorescence image analysis showed that stem-like T cells reside in areas of high antigen-presenting cell density. Tumors with poor T cell infiltration lack APC density, suggesting that an antigen presenting niche is required for a strong T cell response.

Conclusions: Measuring CD8 T cell infiltration in RCC predicts cancer-specific survival, particularly in patients with advanced disease. As this patient population is one for whom improved prognostication is a critical clinical goal, this study represents an opportunity to inform future prognostic measures and to direct reduction or intensification of therapy.

The T cell response was found to be maintained by a population of cells, which harbor both proliferative and differentiation capacity. These stem-like cells require a supportive niche inside the tumor in order to persist, and without this support, the T cell response collapses, resulting in disease progression.

Citation Format: Caroline S. Jansen, Nataliya Prokhnevska, Viraj A. Master, Jennifer W. Carlisle, Mehmet A. Bilen, Adriana M. Reyes, Haydn T. Kissick. CD8 T-cell infiltration into renal tumors requires a supportive antigen-presenting niche [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2700.

Abstract A196: Systematic identification of markers and drug targets on exhausted CD8+ T-cells

CD8+ T-cells are responsible for detection and killing of hosT-cells expressing non-self proteins. Upon antigen persistence, as in cancer or chronic viral infection, antigen-specific CD8+ T-cells lose their effector function, a phenomenon known as T-cell exhaustion. This process is concomitant with increased surface expression of negative regulatory proteins such as PD-1 and CTLA-4. Blockade of these molecules has become a widespread and successful clinical strategy for the treatment of malignancies. Unfortunately, not all tumor types are responsive to checkpoint molecule blockade, nor do all patients with susceptible tumor types exhibit clinical responses. These failures highlight the need for identification of additional negative regulators on exhausted, tumor-specific CD8+ T-cells. Here, we perform a systematic approach to identify surface proteins expressed on exhausted murine and human CD8+ T-cells. Using RNA-sequencing data from antigen-specific CD8+ T-cells from the mouse lymphocytic choriomeningitis virus (LCMV) infection model as well as data from human tumor-infiltrating CD8+ T-cells, we show high cross-species concordance of genes encoding membrane proteins in T-cell exhaustion. These expression profiles not only include many known checkpoint molecules such as PD-1, but also several proteins that negatively regulate T-cell receptor signaling but are largely unexplored in the process of CD8+ T-cell exhaustion. We validate these results performing by flow cytometry on both mouse and human CD8+ T-cells, including on T-cells obtained from resected human tumor tissue. To substantiate the importance of these markers, we further explore the function of one identified surface protein, CD101, in the murine LCMV infection model. We demonstrate that CD101 is induced on antigen-specific of CD8+ T-cells weeks after infection, in contrast with the early expression of canonical exhaustion markers such as PD-1. We show that antigen-specific CD101+ cells arise from CD101- precursors and that this differentiation process results in a loss of effector function, cytokine production, and proliferative capacity with simultaneous large transcriptomic changes. Together, these results demonstrate that exhaustion-associated surface protein expression patterns are largely conserved between humans and mice and provide a comprehensive catalog of phenotypic markers and potential drug targets for CD8+ T-cell-directed immunotherapy.

Citation Format: Will H. Hudson, Julia L. Gensheimer, Haydn T. Kissick, Rafi Ahmed. Systematic identification of markers and drug targets on exhausted CD8+ T-cells [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A196.

The requirement for immune infiltration and organization in the tumor microenvironment for successful immunotherapy in prostate cancer

Immunotherapy-particularly immune checkpoint blockade-has seen great success in many tumor types. However, checkpoint-based therapies have not demonstrated high levels of success in prostate cancer, and there is much to be learned from both the successes and failures of these treatments. Here we review the evidence that composition of infiltrating immune cells in the tumor microenvironment is fundamental to the response to immunotherapy. Additionally, we discuss the emerging idea that the organization of these immune cells may also be crucial to this response. In prostate cancer, the composition and organization of the tumor immune microenvironment are preeminent topics of discussion and areas of important future investigation.

Is It Possible to Develop Cancer Vaccines to Neoantigens, What Are the Major Challenges, and How Can These Be Overcome? Neoantigens as Vaccine Targets for Cancer

Recent work by several groups has undoubtedly shown that we can produce cancer vaccines targeting neoantigens. However, each vaccine is essentially a single-use, patient-specific product, making this approach resource-intensive. For this reason, it is important to ask whether this approach will be any more successful than what has been attempted during the last 30 years using vaccines targeting self-epitopes. Here, we discuss what might be expected from neoantigen vaccines based on our experience in chronic viral infections, and how this new approach may be applied to cancer immunotherapy.

Association Between Pretreatment Neutrophil-to-Lymphocyte Ratio and Outcome of Patients With Metastatic Renal-Cell Carcinoma Treated With Nivolumab

BACKGROUND

Biomarkers to guide treatment in metastatic renal-cell carcinoma (mRCC) are lacking. We aimed to investigate the association between pretreatment neutrophil-to-lymphocyte ratio (NLR) and outcome of patients with mRCC receiving nivolumab.

PATIENTS AND METHODS

Through retrospective chart review, we identified 38 patients with mRCC treated with standard-of-care nivolumab between 2015 and 2016 at Winship Cancer Institute of Emory University. NLR was determined from complete blood count collected before starting treatment, and imaging was performed to assess progression. The NLR cutoff value of 5.5 was determined by log-rank test, and the univariate association with overall survival (OS) or progression-free survival (PFS) was assessed by the Cox proportional hazard model and Kaplan-Meier method.

RESULTS

The 38 patients had a median age of 69 years. The PFS and OS for all patients at 12 months was 54% and 69%, respectively. The median PFS was 2.6 months in the high NLR group but not reached in the low NLR group. Low NLR was strongly associated with increased PFS with hazard ratio of 0.20 (95% confidence interval, 0.07-0.64; P = .006). The median OS was 2.7 months in the high NLR group but not reached in the low NLR group. Low NLR was significantly associated with a prolonged OS with hazard ratio of 0.06 (95% confidence interval, 0.01-0.55; P = .012).

CONCLUSION

Pretreatment NLR < 5.5 is associated with superior PFS and OS. NLR is a biomarker that can inform prognosis for patients with mRCC and should be further validated in larger cohorts and in prospective studies.

Extracellular vesicles from bone marrow-derived mesenchymal stromal cells support ex vivo survival of human antibody secreting cells

Extracellular vesicles (EVs) from bone marrow (BM)-derived mesenchymal stromal cells (BM-MSC) are novel mechanisms of cell-cell communication over short and long distances. BM-MSC have been shown to support human antibody secreting cells (ASC) survival ex vivo, but whether the crosstalk between the MSC-ASC interaction can occur via EVs is not known. Thus, we evaluated the role of EVs in ASC survival and IgG secretion. EVs were isolated from irradiated and non-irradiated primary BM-MSC and were quantified. They were further characterized by electron microscopy (EM) and CD63 and CD81 immuno-gold EM staining. Human ASC were isolated via fluorescence-activated cell sorting (FACS) and cultured ex vivo with the EV fractions, the EV-reduced fractions, or conventional media. IgG Elispots were used to measure the survival and functionality of the ASC. Contents of the EV fractions were evaluated by proteomics. We saw that both irradiated and non-irradiated MSC secretome preparations afforded vesicles of a size consistent with EVs. Both preparations appeared comparable in EM morphology and CD63 and CD81 immuno-gold EM. Both irradiated and non-irradiated EV fractions supported ASC function, at 88% and 90%, respectively, by day 3. In contrast, conventional media maintained only 4% ASC survival by day 3. To identify the specific factors that provided in vitro ASC support, we compared proteomes of the irradiated and non-irradiated EV fractions with conventional media. Pathway analysis of these proteins identified factors involved in the vesicle-mediated delivery of integrin signalling proteins. These findings indicate that BM-MSC EVs provide an effective support system for ASC survival and IgG secretion.

Immunologic profile and prognostic significance of tumor-infiltrating lymphocytes in renal cell carcinoma

673

Background: Renal cell carcinoma (RCC) has been shown to be a genetically and morphologically heterogeneous cancer. As studies show the significance of tumor-infiltrating lymphocytes (TIL) in cancer, it is critical to examine how the phenotype of TILs manifests in RCC. Such analysis may help explain the role of the immune landscape in developing resistance and its contribution to the high treatment failure observed in immunotherapy for RCC. This study compares the immune phenotype of primary tumors, venous tumor thrombi (VTT), and metastases, as well as multiple sites within primary tumors, and investigates whether inter- and intra-tumoral immune heterogeneity is present in RCC. The association of TIL levels and clinical prognosis will also be assessed and compared with current RCC prognostic scores. Methods: Our cohort included 15 VTT and 6 metastases (3 adrenal, 2 bone, 1 liver) with 20 matched primary tumors, as well as 25 non-metastatic primary tumors. The RCC tissue was collected and digested into single cell suspensions. Suspensions were stained for TIL surface markers and processed using flow cytometry. The data was analyzed to capture %CD8+ and %CD4+ in total tumor. The %CD28+ and %PD1+ of CD8+ cells were measured to describe the co-stimulatory and co-inhibitory receptor expression, respectively. Clinical data was obtained to calculate the Mayo Stage, Size, Grade, and Necrosis (SSIGN) and UCLA Integrated Staging System (UISS) scores for each patient and to evaluate recurrence. Results: Immunologic concordance was observed in all measured parameters (%CD8+, %CD4+, %CD28+, and %PD1+) for primary tumors and VTT, for primary tumors and their metastases, and for different sites within 10 primary tumors. In our overall cohort, %CD8+ was found to be inversely associated with recurrence (p = 0.02). Furthermore, %CD8+ was not significantly associated with patient Mayo SSIGN and UISS scores. Conclusions: Despite the genetic and morphologic heterogeneity seen in RCC, immunologic concordance was observed for both inter- and intra-tumoral analysis. The association between %CD8+ and recurrence presents a novel and objective immune-based prognostic factor for RCC, independent of Mayo SSIGN and UISS scores.

Validation of a novel preoperative inflammatory score in localized, clear cell RCC

697

Background: A previously created and analyzed composite renal cell carcinoma (RCC) inflammatory score composed of preoperative serum markers was found to be a significant and independent predictor of overall survival in RCC with accuracy at least as good as other established prognostic tools. The aim of our study was therefore to validate the prognostic significance of this novel score in a new, independent cohort of localized clear cell RCC patients. Methods: A new cohort was randomly selected out of our nephrectomy database from a group of patients with localized clear cell RCC, who underwent nephrectomy from March 2007 to June 2017. Biomarker composition, cutoffs, and calculations of the RCC inflammatory score were accurately recreated from the previous publication. The final score was the sum of points accrued for each biomarker, ranging from 0-10, followed by stratification into baseline (0), low (1-3), intermediate (4-6), and high-risk (7-10) groups. ROC and chi-square analysis were performed to compare the prognostic ability of this novel score to SSIGN, UISS, mGPS, and Leibovich Scores. Impact on overall survival was analyzed with multivariate logistic regression analysis. Results: 252 patients were included in the study. On multivariate analysis, after adjusting for confounding variables, a “high-risk” RCC inflammatory score proved to be an independent and significant predictor of increased mortality (HR = 9.65, 95%CI 1.06-87.79, p = 0.044). At median follow up time, only 45% of high-risk score patients were alive compared with 89-98% of all other patients. Chi-square analysis of c-indices for the RCC inflammatory score and current prognostic scores revealed no statistically significant difference in prognostication of overall survival. Conclusions: Concordant with our previous data, this study reveals that a high-risk RCC inflammatory score is an independent and significant predictor of overall survival in localized clear cell RCC with comparable accuracy to accepted prognostic tools. Distinct from the original study, the high-risk group displayed an even greater association than previously shown, but the intermediate-risk group was no longer significantly different from baseline risk.

Single center validation of neutrophil-to-lymphocyte ratio in localized and metastatic clear cell renal cell carcinoma

696

Background: The neutrophil-to-lymphocyte ratio (NLR) has been evaluated as a serum marker of inflammation and oncologic prognosis. In renal cell carcinoma (RCC), a higher preoperative NLR is associated with aggressive clinicopathologic features and is an independent predictor of poor survival. This study builds upon our institution’s prior work with the NLR in metastatic RCC and examines a larger validation cohort that includes localized disease. It also compares the predictive power of the NLR to established kidney cancer prognostic scores. Methods: Our kidney cancer database provided patients with clear cell RCC who underwent nephrectomy from January 2001 to June 2017 and had a documented preoperative NLR within 15 days prior to surgery. The optimal threshold of NLR was determined using receiver operating characteristic (ROC) curve and sensitivity-specificity trade-off analysis. Kaplan-Meier curves and logistic regression analysis were performed to assess the significance and independence of preoperative NLR in predicting OS. Finally, the prognostic ability of NLR was compared to current prognostic scores through chi-square analysis of their respective c-indices. Results: The 441 patient cohort was comprised of 361 patients with localized and/or regional disease and 80 patients with distant metastases. NLR values among all participants ranged from 0.4 to 74.0 (median 3.1). ROC analysis defined an optimal preoperative NLR threshold of 3.5. On multivariate analysis, after adjusting for clinicopathologic features and distant metastatic disease, a NLR ≥ 3.5 was found to be a significant and independent predictor of overall survival (HR = 1.41, 95% CI 1.05-1.91 & p value = 0.024). Our data also revealed no statistically significant difference between the c-indices of NLR and the UISS, SSIGN, or Leibovich scores in predicting survival. Conclusions: In our validation cohort of patients with both metastatic and non-metastatic clear cell RCC, our data show that a preoperative NLR ≥ 3.5 is a significant and independent predictor of overall survival in patients undergoing nephrectomy and is comparable to other established prognostic tools in RCC.

CD8 T Cell Exhaustion in Chronic Infection and Cancer: Opportunities for Interventions

Antigen-specific CD8 T cells are central to the control of chronic infections and cancer, but persistent antigen stimulation results in T cell exhaustion. Exhausted CD8 T cells have decreased effector function and proliferative capacity, partly caused by overexpression of inhibitory receptors such as programmed cell death (PD)-1. Blockade of the PD-1 pathway has opened a new therapeutic avenue for reinvigorating T cell responses, with positive outcomes especially for patients with cancer. Other strategies to restore function in exhausted CD8 T cells are currently under evaluation-many in combination with PD-1-targeted therapy. Exhausted CD8 T cells comprise heterogeneous cell populations with unique differentiation and functional states. A subset of stem cell-like PD-1⁺ CD8 T cells responsible for the proliferative burst after PD-1 therapy has been recently described. A greater understanding of T cell exhaustion is imperative to establish rational immunotherapeutic interventions.

Evaluation of programmed cell death protein 1 (PD-1) expression as a prognostic biomarker in patients with clear cell renal cell carcinoma

Programmed cell death protein 1 (PD-1) immune checkpoint inhibitors have shown activity in patients with advanced renal cell carcinoma (RCC). However, the role of PD-1 expression in tumor-infiltrating lymphocytes (TILs) as a biomarker for poor outcome is not clear. In this study, we evaluated the prognostic value of TIL PD-1 expression in patients with clear cell RCC (ccRCC). 82 patients who underwent nephrectomy for localized or metastatic ccRCC and followed up for at least four years were searched from our database and retrospectively enrolled. Their fixed primary tumor specimens were stained with anti-PD-1 (NAT105). The specimens were classified as negative or positive for PD-1 expression, and the positive specimens were further scored in 10% increments. 37 (45.12%) patients were negative (<1% stained), 26 (31.71%) patients were low (<10 and 10%), and 19 (23.17%) patients were high (20-50%) for PD-1 expression. The prognostic value of TIL PD-1 expression was evaluated by univariate Cox proportional hazards regression on overall and recurrence-free survivals. Higher TIL PD-1 expression was not associated with increased risk of death (P = 0.336) or with increased risk of recurrence (P = 0.572). Higher primary tumor stage was associated with increased risk of recurrence (P = 0.003), and higher Fuhrman nuclear grade was associated with increased risk of death (P <0.001) and with increased risk of recurrence (P <0.001). Our study shows that TIL PD-1 expression by immunohistochemistry (IHC) does not correlate with poor clinical outcome in patients with ccRCC and is inferior to established prognosticating tools.

Targeted Therapies: Immunologic Effects and Potential Applications Outside of Cancer

Two pharmacologic approaches that are currently at the forefront of treating advanced cancer are those that center on disrupting critical growth/survival signaling pathways within tumor cells (commonly referred to as "targeted therapies") and those that center on enhancing the capacity of a patient's immune system to mount an antitumor response (immunotherapy). Maximizing responses to both of these approaches requires an understanding of the oncogenic events present in a given patient's tumor and the nature of the tumor-immune microenvironment. Although these 2 modalities were developed and initially used independently, combination regimens are now being tested in clinical trials, underscoring the need to understand how targeted therapies influence immunologic events. Translational studies and preclinical models have demonstrated that targeted therapies can influence immune cell trafficking, the production of and response to chemokines and cytokines, antigen presentation, and other processes relevant to antitumor immunity and immune homeostasis. Moreover, because these and other effects of targeted therapies occur in nonmalignant cells, targeted therapies are being evaluated for use in applications outside of oncology.

Effector CD8 T cells dedifferentiate into long-lived memory cells

Memory CD8 T cells that circulate in the blood and are present in lymphoid organs are an essential component of long-lived T cell immunity. These memory CD8 T cells remain poised to rapidly elaborate effector functions upon re-exposure to pathogens, but also have many properties in common with naive cells, including pluripotency and the ability to migrate to the lymph nodes and spleen. Thus, memory cells embody features of both naive and effector cells, fuelling a long-standing debate centred on whether memory T cells develop from effector cells or directly from naive cells. Here we show that long-lived memory CD8 T cells are derived from a subset of effector T cells through a process of dedifferentiation. To assess the developmental origin of memory CD8 T cells, we investigated changes in DNA methylation programming at naive and effector cell-associated genes in virus-specific CD8 T cells during acute lymphocytic choriomeningitis virus infection in mice. Methylation profiling of terminal effector versus memory-precursor CD8 T cell subsets showed that, rather than retaining a naive epigenetic state, the subset of cells that gives rise to memory cells acquired de novo DNA methylation programs at naive-associated genes and became demethylated at the loci of classically defined effector molecules. Conditional deletion of the de novo methyltransferase Dnmt3a at an early stage of effector differentiation resulted in reduced methylation and faster re-expression of naive-associated genes, thereby accelerating the development of memory cells. Longitudinal phenotypic and epigenetic characterization of the memory-precursor effector subset of virus-specific CD8 T cells transferred into antigen-free mice revealed that differentiation to memory cells was coupled to erasure of de novo methylation programs and re-expression of naive-associated genes. Thus, epigenetic repression of naive-associated genes in effector CD8 T cells can be reversed in cells that develop into long-lived memory CD8 T cells while key effector genes remain demethylated, demonstrating that memory T cells arise from a subset of fate-permissive effector T cells.

Correlation between inflammatory markers in blood and expression of costimulatory molecules on tumor-infiltrating CD8+ lymphocytes in renal cell carcinoma

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Background: Loss of co-stimulatory molecules by CD8 T-cells is associated with reduced proliferative and cytotoxic function in chronic viral infections, aging, and cancer. Several lines of evidence suggest that a more functional immune system is associated with better patient outcomes, and improved response to immunotherapy in a range of different cancers. For this reason, understanding the features of a patient that predict the loss of T-cell function is important. In this study we characterized how co-stimulatory molecules are expressed by T-cells in the tumors of RCC patients. Additionally, we characterized how distant sites of metastasis differ from the primary tumor, and finally, we evaluated levels of blood inflammatory markers (BIMs) to predict how co-stimulatory on CD8+ TILs change. Methods: Patients that underwent resection of primary and/or metastatic RCC at Emory University Hospital were prospectively enrolled in the study. Levels of pre-op BIMs were retrieved from medical records. A portion of resected tumor tissue was analyzed by flow cytometry to measure percentage of CD8+ cells expression of the co-stimulatory molecules, ICOS, CD27, CD40L, CD226, CD28, and CD2. A composite co-stimulatory score (co-stim score) was calculated by taking a weighted average of the number of co-stimulatory receptors expressed per cell. BIMs were correlated with CD28 expression and co-stim score. Expression of co-stimulatory receptors was compared between patient-matched primary tumor and metastatic tumor pairs. Results: We found that by CD8 T-cells in tumors often lost co-stimulatory molecules. Furthermore, albumin and Hgb both had a strong positive correlation with CD28 expression and overall co-stim score, while WBC, Plt, neutrophil-lymphocyte ratio (NLR), ESR, and CRP was negatively correlated. Expression of co-stimulatory receptors did not differ significantly between primary tumor and metastatic tumor pairs suggesting that a systemic effect controlled TIL phenotype rather than site specific factors. Conclusions: Our data show that BIMs have the potential to predict the immunologic phenotypes of cytotoxic TILs in RCC noninvasively.

Gleason Score 7 Prostate Cancers Emerge through Branched Evolution of Clonal Gleason Pattern 3 and 4

Purpose: The molecular features that account for the distinct histology and aggressive biological behavior of Gleason pattern 4 (Gp4) versus Gp3 prostate cancer, and whether Gp3 tumors progress directly to Gp4, remain to be established.Experimental Design: Whole-exome sequencing and transcriptome profiling of laser capture-microdissected adjacent Gp3 and cribiform Gp4 were used to determine the relationship between these entities.Results: Sequencing confirmed that adjacent Gp3 and Gp4 were clonal based on multiple shared genomic alterations. However, large numbers of unique mutations in the Gp3 and Gp4 tumors showed that the Gp4 were not derived directly from the Gp3. Remarkably, the Gp3 tumors retain their indolent-appearing morphology despite acquisition of multiple genomic alterations, including tumor suppressor losses. Although there were no consistent genomic alterations that distinguished Gp3 from Gp4, pairwise transcriptome analyses identified increased c-Myc and decreased p53 activity in Gp4 versus adjacent clonal Gp3 foci.Conclusions: These findings establish that at least a subset of Gp3 and aggressive Gp4 tumors have a common origin, and support a branched evolution model wherein the Gp3 and Gp4 tumors emerge early from a common precursor and subsequently undergo substantial divergence. Genomic alterations detectable in the Gp3 may distinguish these tumors from truly indolent Gp3. Screening for a panel of these genomic alterations in men who have prostate biopsies showing only Gp3 (Gleason score 6, Gs6) may allow for more precise selection of men who can be safely managed by active surveillance versus those who may benefit from further intervention. Clin Cancer Res; 23(14); 3823-33. ©2017 AACR.

Understanding the Impact of ErbB Activating Events and Signal Transduction on Antigen Processing and Presentation: MHC Expression as a Model

Advances in molecular pathology have changed the landscape of oncology. The ability to interrogate tissue samples for oncogene amplification, driver mutations, and other molecular alterations provides clinicians with an enormous level of detail about their patient's cancer. In some cases, this information informs treatment decisions, especially those related to targeted anti-cancer therapies. However, in terms of immune-based therapies, it is less clear how to use such information. Likewise, despite studies demonstrating the pivotal role of neoantigens in predicting responsiveness to immune checkpoint blockade, it is not known if the expression of neoantigens impacts the response to targeted therapies despite a growing recognition of their diverse effects on immunity. To realize the promise of 'personalized medicine', it will be important to develop a more integrated understanding of the relationships between oncogenic events and processes governing anti-tumor immunity. One area of investigation to explore such relationships centers on defining how ErbB/HER activation and signal transduction influences antigen processing and presentation.

Defining CD8+ T cells that provide the proliferative burst after PD-1 therapy

Chronic viral infections are characterized by a state of CD8⁺ T-cell dysfunction that is associated with expression of the programmed cell death 1 (PD-1) inhibitory receptor. A better understanding of the mechanisms that regulate CD8⁺ T-cell responses during chronic infection is required to improve immunotherapies that restore function in exhausted CD8⁺ T cells. Here we identify a population of virus-specific CD8⁺ T cells that proliferate after blockade of the PD-1 inhibitory pathway in mice chronically infected with lymphocytic choriomeningitis virus (LCMV). These LCMV-specific CD8⁺ T cells expressed the PD-1 inhibitory receptor, but also expressed several costimulatory molecules such as ICOS and CD28. This CD8⁺ T-cell subset was characterized by a unique gene signature that was related to that of CD4⁺ T follicular helper (T_FH) cells, CD8⁺ T cell memory precursors and haematopoietic stem cell progenitors, but that was distinct from that of CD4⁺ T_H1 cells and CD8⁺ terminal effectors. This CD8⁺ T-cell population was found only in lymphoid tissues and resided predominantly in the T-cell zones along with naive CD8⁺ T cells. These PD-1⁺CD8⁺ T cells resembled stem cells during chronic LCMV infection, undergoing self-renewal and also differentiating into the terminally exhausted CD8⁺ T cells that were present in both lymphoid and non-lymphoid tissues. The proliferative burst after PD-1 blockade came almost exclusively from this CD8⁺ T-cell subset. Notably, the transcription factor TCF1 had a cell-intrinsic and essential role in the generation of this CD8⁺ T-cell subset. These findings provide a better understanding of T-cell exhaustion and have implications in the optimization of PD-1-directed immunotherapy in chronic infections and cancer.

Major histocompatibility complex I upregulation in clear cell renal cell carcinoma is associated with increased survival

Objective

To examine the prognostic value of tumor major histocompatibility complex I (MHCI) expression on survival and recurrence in patients with clear cell renal cell carcinoma (RCC).

Methods

Fifty-three patients that underwent nephrectomy at our institution for clear cell RCC (T1-T3) with ≥4 years of follow-up were queried from our nephrectomy database. Immunohistochemical staining for MHCI was performed on tumor specimens and MHCI expression was quantified with an automated image analysis technique. Patients were divided into high and low MHCI expression groups in order to study the relationship between MHCI expression and prognosis using the Kaplan-Meier method and log-rank test.

Results

Overall survival and recurrence free survival were increased in the high MHCI expression group compared to the low MHCI expression group (log-rank, p = 0.036 and p = 0.028, respectively). Patients alive at the end of the study had higher MHCI expression (mean positivity score 0.82) than those that died of disease (mean positivity score 0.76, t test, p = 0.030). Patients that did not develop recurrence during the study period had higher MHCI expression (mean positivity score 0.83) than those that did develop recurrence (mean positivity score 0.78), but this difference was not significant (t test, p = 0.079).

Conclusion

Our data demonstrate that high MHCI expression confers improved overall and recurrence free survival in patients with clear cell RCC and could serve as an important prognostic tool in identifying high-risk patients.

Application of small RNA sequencing to identify microRNAs in acute kidney injury and fibrosis

Establishing a microRNA (miRNA) expression profile in affected tissues provides an important foundation for the discovery of miRNAs involved in the development or progression of pathologic conditions. We conducted small RNA sequencing to generate a temporal profile of miRNA expression in the kidneys using a mouse model of folic acid-induced (250mg/kgi.p.) kidney injury and fibrosis. From the 103 miRNAs that were differentially expressed over the time course (>2-fold, p<0.05), we chose to further investigate miR-18a-5p, which is expressed during the acute stage of the injury; miR-132-3p, which is upregulated during transition between acute and fibrotic injury; and miR-146b-5p, which is highly expressed at the peak of fibrosis. Using qRT-PCR, we confirmed the increased expression of these candidate miRNAs in the folic acid model as well as in other established mouse models of acute injury (ischemia/reperfusion injury) and fibrosis (unilateral ureteral obstruction). In situ hybridization confirmed high expression of miR-18a-5p, miR-132-3p and miR-146b-5p throughout the kidney cortex in mice and humans with severe kidney injury or fibrosis. When primary human proximal tubular epithelial cells were treated with model nephrotoxicants such as cadmium chloride (CdCl₂), arsenic trioxide, aristolochic acid (AA), potassium dichromate (K₂Cr₂O₇) and cisplatin, miRNA-132-3p was upregulated 4.3-fold after AA treatment and 1.5-fold after K₂Cr₂O₇ and CdCl₂ treatment. These results demonstrate the application of temporal small RNA sequencing to identify miR-18a, miR-132 and miR-146b as differentially expressed miRNAs during distinct phases of kidney injury and fibrosis progression.

Bone metastasis in prostate cancer: Recurring mitochondrial DNA mutation reveals selective pressure exerted by the bone microenvironment

BACKGROUND

Cancer progression and metastasis occur such that cells with acquired mutations enhancing growth and survival (or inhibiting cell death) increase in number, a concept that has been recognized as analogous to Darwinian evolution of species since Peter C. Nowell's description in 1976. Selective forces include those intrinsic to the host (including metastatic site) as well as those resulting from anti-cancer therapies. By examining the mutational status of multiple tumor sites within an individual patient some insight may be gained into those genetic variants that enhance site-specific metastasis. By comparing these data across multiple individuals, recurrent patterns may identify alterations that are fundamental to successful site-specific metastasis.

METHODS

We sequenced the mitochondrial genome in 10 prostate cancer patients with bone metastases enrolled in a rapid autopsy program. Patients had late stage disease and received androgen ablation and frequently other systemic therapies. For each of 9 patients, 4 separate tissues were sequenced: the primary prostate cancer, a soft tissue metastasis, a bone metastasis and an uninvolved normal tissue that served as the non-cancerous control. An additional (10th) patient had no primary prostate available for sequencing but had both metastatic sites (and control DNA) sequenced. We then examined the number and location of somatically acquired mitochondrial DNA (mtDNA) mutations in the primary tumor and two metastatic sites in each individual patient. Finally, we compared patients with each other to determine any common patterns of somatic mutation.

RESULTS

Somatic mutations were significantly more numerous in the bone compared to either the primary tumor or soft tissue metastases. A missense mutation at nucleotide position (n.p.) 10398 (A10398G; Thr114Ala) in the respiratory complex I gene ND3 was the most common (7 of 10 patients) and was detected only in the bone. Other notable somatic mutations that occurred in more than one patient include a tRNA Arg mutation at n.p. 10436 and a tRNA Thr mutation at n.p. 15928. The tRNA Arg mutation was restricted to bone metastases and occurred in three of 10 patients (30%). Somatic mutation at 15928 was not restricted to the bone and also occurred in three patients.

CONCLUSIONS

Mitochondrial genomic variation was greater in metastatic sites than in the primary tumor and bone metastases had statistically significantly greater numbers of somatic mutations than either the primary or the soft tissue metastases. The genome was not mutated randomly. At least one mutational "hot-spot" was identified at the individual base level (nucleotide position 10398 in bone metastases) indicating a pervasive selective pressure for bone metastatic cells that had acquired the 10398 mtDNA mutation. Two additional recurrent mutations (tRNA Arg and tRNA Thr) support the concept of bone site-specific "survival of the fittest" as revealed by variation in the mitochondrial genome and selective pressure exerted by the metastatic site.

The transcription factor ERG increases expression of neurotransmitter receptors on prostate cancer cells

Background

The TMPRSS2-ERG gene fusion occurs in about half of prostate cancer (PCa) cases and results in overexpression of the transcription factor ERG. Overexpression of ERG has many effects on cellular function. However, how these changes enhance cell growth and promote tumor development is unclear.

Methods

To investigate the role of ERG, LNCaP and PC3 cells were transfected with ERG and gene expression and metabolic profile were analyzed.

Results

Our data show that expression of ERG induces overexpression of many nicotinicacetylcholine receptors (nAChRs). In addition, metabolic profiling by LC-MS/MS revealed elevated production of several neurotransmitters in cells expressing ERG. Consistently, treatment of ERG-expressing cells with nicotine induced elevated calcium influx, GSK3β (Ser9) phosphorylation and cell proliferation. Finally, we show that PCa patientswho are smokers have larger tumors if their tumors are TMPRSS2-ERG gene fusion positive.

Conclusion

Collectively, our data suggest that ERG sensitizes prostate tumor cells to neurotransmitter receptor agonists like nicotine.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1612-3) contains supplementary material, which is available to authorized users.

The role of active vaccination in cancer immunotherapy: lessons from clinical trials

In the past few years, a number of different immunotherapeutic strategies have shown impressive results in cancer patients. These successful approaches include blockade of immunosuppressive molecules like PD-1 and CTLA-4, adoptive transfer of patient derived and genetically modified T-cells, and vaccines that stimulate tumor antigen specific T-cells. However, several large vaccine trials recently failed to reach designated primary endpoints. In light of the success of other immunotherapeutic approaches, these negative results raise the questions of why vaccines have not generated a better response, and what the role of active vaccination will be moving forward in cancer immunotherapy.

Beyond immune checkpoint blockade: new approaches to targeting host-tumor interactions in prostate cancer: report from the 2014 Coffey-Holden prostate cancer academy meeting

INTRODUCTION

The 2014 Coffey-Holden Prostate Cancer Academy Meeting, held in La Jolla, CA from June 26 to 29, 2014, was themed: "Beyond Immune Checkpoint Blockade: New Approaches to Targeting Host-Tumor Interactions in Prostate Cancer."

METHODS

Sponsored by the Prostate Cancer Foundation (PCF), this annual, invitation-only meeting is structured as an action-tank, and brought together 72 investigators with diverse academic backgrounds to discuss the most relevant topics in the fields of prostate cancer immunotherapy and the tumor microenvironment.

RESULTS

The questions addressed at the meeting included: mechanisms underlying the successes and failures of prostate cancer immunotherapies, how to trigger an effective immune response against prostate cancer, the tumor microenvironment and its role in therapy resistance and tumor metastasis, clinically relevant prostate cancer mouse models, how host-tumor interactions affect current therapies and tumor phenotypes, application of principles of precision medicine to prostate cancer immunotherapy, optimizing immunotherapy clinical trial design, and complex multi-system interactions that affect prostate cancer and immune responses including the effects of obesity and the potential role of the host microbiome.

DISCUSSION

This article highlights the most significant recent progress and unmet needs that were discussed at the meeting toward the goal of speeding the development of optimal immunotherapies for the treatment of prostate cancer.