The promise of immunotherapy in head and neck squamous cell carcinoma

Diagnostic Tumor Markers in Head and Neck Squamous Cell Carcinoma (HNSCC) in the Clinical Setting

Head and neck squamous cell carcinoma (HNSCC) represents a group of tumors arising in the oral cavity, oropharynx, and larynx. Although HNSCC is traditionally associated with tobacco and alcohol consumption, a growing proportion of head and neck tumors, mainly of the oropharynx, are associated with Human Papilloma Virus (HPV). Recurrent/metastatic disease is characterized by dismal prognosis and there is an unmet need for the development of biomarkers for detection of early disease, accurate prediction of prognosis, and appropriate selection of therapy. Based on the REMARK guidelines, a variety of diagnostic and prognostic biomarkers are being evaluated in clinical trials but their clinical significance is doubtful. Herein, we will focus on biomarkers in HNSCC used in the clinical setting and we will illustrate their clinical relevance.

Expression of PD-L1 on Immune Cells Shows Better Prognosis in Laryngeal, Oropharygeal, and Hypopharyngeal Cancer

Despite great enthusiasm towards immunotherapy, reliable biomarkers are still lacking. The importance of subsets based on human papillomavirus (HPV) status is supported by a growing body of evidence. However, role of other possible subgroups such as anatomic localization of primary tumor remains controversial. Our objective was to investigate immune cell infiltrate and checkpoint inhibitor proteins in above-mentioned head and neck cancer subsets. Archival tumor samples of 106 laryngeal, oropharyngeal, and hypopharyngeal cancer patients were stained with PD-L1, PD-L2, PD-1, and CTLA-4 antibodies. Proportion of tumor-infiltrating lymphocytes was assessed as well. In HPV-negative tumors, PD-L1 immune cell positivity was associated with better disease-specific survival. PD-L1 expression on immune cells correlated with improved disease-specific survival in laryngeal tumors. Furthermore, PD-L1 immune cell positivity correlated with CTLA-4 expression on immune cells and it was accompanied by high tumor-infiltrating lymphocyte rate. PD-L1 expression on tumor cells and PD-1 status showed strong correlation in all patients and in oropharyngeal and laryngeal localization, but not in hypopharynx. HPV-negative oropharyngeal cancers showed negative PD-L1 status on tumor cells. CTLA-4 positivity was observed in 49.5% and 20.6% on immune cells and on tumor cells, respectively. We concluded that PD-L1 expression on immune cells indicates better prognosis in laryngeal squamous cell carcinoma and in HPV-negative head and neck squamous cell carcinoma. We have not found any essential differences between anatomic subgroups. A possibly distinct role of hypopharyngeal localization regarding immune activity requires further clarification.

Impact of combination immunochemotherapies on progression of 4NQO-induced murine oral squamous cell carcinoma

Advanced oral squamous cell carcinomas (OSCC) have limited therapeutic options. Although immune therapies are emerging as a potentially effective alternative or adjunct to chemotherapies, the therapeutic efficacy of combination immune chemotherapies has yet to be determined. Using a 4-nitroquinolone-N-oxide (4NQO) orthotopic model of OSCC in immunocompetent mice, we evaluated the therapeutic efficacy of single- and combined-agent treatment with a poly-epitope tumor peptide vaccine, cisplatin and/or an A2AR inhibitor, ZM241385. The monotherapies or their combinations resulted in a partial inhibition of tumor growth and, in some cases, a significant but transient upregulation of systemic anti-tumor CD8+ T cell responses. These responses eroded in the face of expanding immunoregulatory cell populations at later stages of tumor progression. Our findings support the need for the further development of combinatorial therapeutic approaches that could more effectively silence dominant immune inhibitory pathways operating in OSCC and provide novel, more beneficial treatment options for this tumor.

Not CD68 but stabilin-1 expression is associated with the risk of recurrence in patients with oral cavity squamous cell carcinoma

BACKGROUND

This study's aim was to identify CD68 and stabilin-1 expressions and their prognostic implications in patients with oral cavity cancer (OCC).

METHODS

Stabilin-1 and CD68 immunochemical staining was conducted in samples from patients with OCC who underwent curative surgery in our institute. We retrospectively analyzed patients' clinical information. We investigated the relationship between CD68 and stabilin-1 expression levels and their effect on prognostic factors and survival.

RESULTS

Fifty-four patients' data were analyzed. CD68 and stabilin-1 expressions were positively correlated (P = .008). CD68 and stabilin-1 expressions were not correlated with other prognostic factors (eg, T classification or lymph node metastasis). Stabilin-1 expression and tumor recurrence risk were positively correlated (P = .015). CD68 expression was neither associated with recurrence-free nor OCC-specific survival.

CONCLUSION

CD68 and stabilin-1 expressions in OCC were positively correlated. Stabilin-1 expression was significantly associated with OCC recurrence risk, but the prognostic value of CD68 was not confirmed.

Time for radioimmunotherapy: an overview to bring improvements in clinical practice

Harnessing the patient's own immune system against an established cancer has proven to be a successful strategy. Within the last years, several antibodies blocking critical "checkpoints" that control the activation of T cells, the immune cells able to kill cancer cells, have been approved for the use in patients with different tumours. Unfortunately, these cases remain a minority. Over the last years, radiotherapy has been reported as a means to turn a patient's own tumour into an in situ vaccine and generate anti-tumour T cells in patients who lack sufficient anti-tumour immunity. Indeed, review data show that the strategy of blocking multiple selected immune inhibitory targets in combination with radiotherapy has the potential to unleash powerful anti-tumour responses and improve the outcome of metastatic solid tumours. Here, we review the principal tumours where research in this field has led to new knowledge and where radioimmunotherapy becomes a reality.

The value of immunotherapy in head and neck cancer

INTRODUCTION

Head and neck squamous cell carcinomas (HNSCC) previously had limited treatment options once patients had progressed on systemic chemotherapy. With recent advances, immunotherapy now plays an important role in the treatment of advanced disease with improved outcomes as compared to cytotoxic chemotherapy.

AREAS COVERED

This article reviews the effects of the immune system and how it influences the development and response to HNSCC therapy. We additionally provide a summary of immunotherapy treatments available as well as their applicable clinical trials that led to their approval.

EXPERT COMMENTARY

The challenges that need to be addressed in order to maximize the benefits of immunotherapy in HNSCC are the selection criteria for immune checkpoint inhibitors and the optimization of combination regimens of immunotherapeutics or chemo-immunotherapy. Furthermore, there remains to be a lack of knowledge in how to incorporate molecular biomarkers as predictors of response to HNSCC immunotherapy.

γδTDEs: An Efficient Delivery System for miR-138 with Anti-tumoral and Immunostimulatory Roles on Oral Squamous Cell Carcinoma

In this study, we sought to investigate the potential application of γδ T cell-derived extracellular vesicles (γδTDEs) as drug delivery system (DDS) for miR-138 in the treatment of oral squamous cell carcinoma (OSCC). Our data showed that overexpression of miR-138 in γδ T cells obtained miR-138-rich γδTDEs accompanying increased expansion and cytotoxicity of γδ T cells. γδTDEs inherited the cytotoxic profile of γδ T cells and could efficiently deliver miR-138 to OSCC cells, resulting in synergetic inhibition on OSCC both in vitro and in vivo. The pre-immunization by miR-138-rich γδTDEs inhibited the growth of OSCC tumors in immunocompetent C3H mice, but not in nude mice, suggesting an immunomodulatory role by miR-13-rich γδTDEs. γδTDEs and miR-138 additively increased the proliferation, interferon-γ (IFN-γ) production, and cytotoxicity of CD8⁺ T cells against OSCC cells. Only delivered by γδTDEs can miR-138 efficiently target programmed cell death 1 (PD-1) and CTLA-4 in CD8⁺ T cells. We conclude that γδTDEs delivering miR-138 could achieve synergetic therapeutic effects on OSCC, which is benefited from the individual direct anti-tumoral effects on OSCC and immunostimulatory effects on T cells by both γδTDEs and miR-138; γδTDEs could serve as an efficient DDS for microRNAs (miRNAs) in the treatment of cancer.

Inhibition of SRC family kinases facilitates anti-CTLA4 immunotherapy in head and neck squamous cell carcinoma

The immune system plays a critical role in the establishment, development, and progression of head and neck squamous cell carcinoma (HNSCC). As treatment with single-immune checkpoint agent results in a lower response rate in patients, it is important to investigate new strategies to maintain favorable anti-tumor immune response. Herein, the combination immunotherapeutic value of CTLA4 blockade and SFKs inhibition was assessed in transgenic HNSCC mouse model. Our present work showed that tumor growth was not entirely controlled when HNSCC model mice were administered anti-CTLA4 chemotherapeutic treatment. Moreover, it was observed that Src family kinases (SFKs) were hyper-activated and lack of anti-tumor immune responses following anti-CTLA4 chemotherapeutic treatment. We hypothesized that activation of SFKs is a mechanism of anti-CTLA4 immunotherapy resistance. We, therefore, carried out combined drug therapy using anti-CTLA4 mAbs and an SFKs' inhibitor, dasatinib. As expected, dasatinib and anti-CTLA4 synergistically inhibited tumor growth in Tgfbr1/Pten 2cKO mice. Furthermore, dasatinib and anti-CTLA4 combined to reduce the number of myeloid-derived suppressor cells and Tregs, increasing the CD8+ T cell-to-Tregs ratio. We also found that combining dasatinib with anti-CTLA4 therapy significantly attenuated the expression of p-STAT3Y705 and Ki67 in tumoral environment. These results suggest that combination therapy with SFKs inhibitors may be a useful therapeutic approach to increase the efficacy of anti-CTLA4 immunotherapy in HNSCC.

Inhibition of MEK with trametinib enhances the efficacy of anti-PD-L1 inhibitor by regulating anti-tumor immunity in head and neck squamous cell carcinoma

Major histocompatibility complex (MHC) class I downregulation is the primary immune evasion mechanism associated with failure in anti-PD-1/PD-L1 blockade therapies for cancer. Here, we examined the role of MEK signaling pathway inhibition in head and neck squamous cell carcinoma (HNSCC) both in vitro and in vivo. We found that trametinib, a small molecule inhibitor of MEK, significantly enhanced MHC class I and PD-L1 expression in human HNSCC cell lines, and this occurred via STAT3 activation. Trametinib also further upregulated the increase in CXCL9 and CXCL10 expression caused by IFN-γ in HNSCC cells, which is associated with T cell infiltration in tumor tissues. Finally, we evaluated the therapeutic efficacy of trametinib combined with an anti-PD-L1 monoclonal antibody in vivo, using SCCVII mouse syngeneic tumor model for HNSCC. While neither PD-L1 blockade nor trametinib treatment alone affected tumor growth, the combined therapy significantly delayed tumor growth. Our results indicate that in the combined therapy trametinib increases CD8⁺ T cell infiltration in the tumor site and upregulates antigen presentation, and this may be associated with enhanced PD-L1 blockade efficacy. Furthermore, our results suggest that this combination would therapeutically benefit patients with HNSCC.

Post-operative radiation effects on lymphopenia, neutrophil to lymphocyte ratio, and clinical outcomes in palatine tonsil cancers

OBJECTIVE

To evaluate radiation-induced lymphopenia associated with unilateral vs. bilateral neck radiation and to test post-treatment neutrophil to lymphocyte ratio (NLR) as a prognostic clinical biomarker.

METHODS

This was a single academic center retrospective review of palatine tonsil squamous cell cancer patients treated with post-operative intensity modulated radiation therapy (IMRT) from 1997 to 2013. Absolute lymphocyte count (ALC) and NLR were evaluated during and after radiation for up to a year. Correlations of lab values with loco-regional control (LRC), freedom from distant metastases (FFDM), and overall survival (OS) were assessed.

RESULTS

Ninety-nine patients with median follow up 5.8 years had ALC recorded at least at baseline and within one year of starting RT. Acute grade 3-4 lymphopenia (<10 weeks from RT start) occurred in 79% of bilateral neck RT patients (n = 70) and 58% of unilateral neck RT patients (n = 29), p = 0.03. There was no significant difference in late grade 3-4 (p = 0.12) lymphopenia. In a multivariable Cox regression model, acute NLR > 11.875 correlated with worse OS (HR = 4.4, 95% CI 1.2-16). Late NLR > 6.875 independently correlated with significantly worse FFDM (HR = 16, 95% CI 1.9-137) and OS (HR = 12, 95% CI 3.0-48).

CONCLUSIONS

Unilateral neck radiation may prevent acute iatrogenic immunosuppression. In exploratory analyses, elevated post-treatment NLR was associated with risk for distant metastases and death.

The immune microenvironment of HPV-negative oral squamous cell carcinoma from never-smokers and never-drinkers patients suggests higher clinical benefit of IDO1 and PD1/PD-L1 blockade

Background

Never-smokers and never-drinkers patients (NSND) suffering from oral squamous cell carcinoma (OSCC) are epidemiologically different from smokers drinkers (SD). We therefore hypothesized that they harbored distinct targetable molecular alterations.

Patients and methods

Data from The Cancer Genome Atlas (TCGA) (discovery set), Gene Expression Omnibus and Centre Léon Bérard (CLB) (three validation sets) with available gene expression profiles of HPV-negative OSCC from NSND and SD were mined. Protein expression profiles and genomic alterations were also analyzed from TCGA, and a functional pathway enrichment analysis was carried out. Formalin-fixed paraffin-embedded samples from 44 OSCC including 20 NSND and 24 SD treated at CLB were retrospectively collected to perform targeted-sequencing of 2559 transcripts (HTG EdgeSeq system), and CD3, CD4, CD8, IDO1, and PD-L1 expression analyses by immunohistochemistry (IHC). Enrichment of a six-gene interferon-γ signature of clinical response to pembrozulimab (PD-1 inhibitor) was evaluated in each sample from all cohorts, using the single sample gene set enrichment analysis method.

Results

A total of 854 genes and 29 proteins were found to be differentially expressed between NSND and SD in TCGA. Functional pathway analysis highlighted an overall enrichment for immune-related pathways in OSCC from NSND, especially involving T-cell activation. Interferon-γ response and PD1 signaling were strongly enriched in NSND. IDO1 and PD-L1 were overexpressed and the score of response to pembrolizumab was higher in NSND than in SD, although the mutational load was lower in NSND. IHC analyses in the CLB cohort evidenced IDO1 and PD-L1 overexpression in tumor cells that was associated with a higher rate of tumor-infiltrating T-cells in NSND compared with SD.

Conclusion

The main biological and actionable difference between OSCC from NSND and SD lies in the immune microenvironment, suggesting a higher clinical benefit of PD-L1 and IDO1 inhibition in OSCC from NSND.

Curcumin enhances anti-tumor immune response in tongue squamous cell carcinoma

PURPOSE

This study evaluated the role of anti-tumor immune response of curcumin on tongue squamous cell carcinama (TSCC).

EXPERIMENTAL DESIGN

Cell lines (Cal 27, FaDu) and animal model (4NQO mice model) were uesd in this study. The MTT assay was used to detecte cell proliferation. The Western blotting, immunohistochemistry and immunofluorescence were used to examine the protein expression. The flow cytometry was performed to determine the number of Treg and MDSC.

RESULTS

The expression of PD-L1 and p-STAT3^Y705 were does-dependently inhibited in Fadu and Cal 27 cell line. The results of in vivo demonstrated that curcumin significantly attenuated tumor growth in 4NQO mice model. The expression of PD-L1 and p-STAT3^Y705 were similarly decreased in vivo. Moreover, the anti-tumor immune response was remarkably improved after curcumin treatment through increasing CD8 positive T cells and decreasing Tregs and MDSCs.

CONCLUSIONS

Curcumin treatment resulted in inhibition of PD-L1 and p-STAT3^Y705 expression both in vitro and in vivo. Moreover, the immunosuppressive tumor microenvironment was changed after curcumin treatment. These data suggested that curcumin could effectively promote anti-tumor immune response in TSCC.

miR‑3147 serves as an oncomiR in vulvar squamous cell cancer via Smad4 suppression

The incidence of vulvar squamous cell carcinoma (VSCC) has increased annually over the last decade. MicroRNAs (miRNAs/miRs) serve an important role in tumor progression and development. Our previous microarray studies have revealed that miR-3147 was overexpressed in VSCC. However, its function and underlying mechanism in VSCC remain unknown. In the present study, it was confirmed by reverse transcription-quantitative polymerase chain reaction that the expression of miR-3147 was markedly upregulated in VSCC tissues. The increased expression of miR-3147 was positively associated with the depth of invasion. The overexpression of miR-3147 resulted in the promotion of vulvar cancer cell proliferation, migration, invasion, G1/S progression and invasion-associated gene expression. miR-3147 may participate in the process of epithelial-mesenchymal transition and reduce the expressions of downstream target genes in the transforming growth factor-β/Smad signaling pathway in A431 cells. The knockdown of Smad4 by small interfering RNA promoted malignant behaviours in A431 cells. In addition, miR-3147 regulated Smad4 by directly binding to its 3′ untranslated region. In conclusion, the results indicated that miR-3147 may serve an oncogenic role in VSCC by targeting Smad4. miR-3147 may represent a novel potential therapeutic target marker for VSCC.

Programmed death ligand-1 expression as immunotherapeutic target in sinonasal cancer

BACKGROUND

Sinonasal cancer carries a poor prognosis, especially in recurrent stages, and it is a disease with very limited treatment options.

METHODS

The expression of programmed death ligand-1 (PD-L1) as a marker for immunotherapy was evaluated in 53 sinonasal squamous cell carcinoma (SCC) and 126 intestinal-type adenocarcinoma (ITAC) samples. Results were correlated to clinicopathological characteristics and follow-up data.

RESULTS

Membranous PD-L1 staining of tumor cells was observed in 34% (18/53) of the sinonasal SCC samples and in 17% (22/126) of the ITAC samples. The PD-L1 positivity on infiltrating immune cells occurred in 45% (24/53) of the sinonasal SCC samples and in 33% (41/126) of the ITAC samples. Expression of PD-L1 showed no correlation to clinicopathological parameters and was not an independent risk factor for survival.

CONCLUSION

The PD-L1 positivity does not seem to have prognostic value. However, a proportion of patients with sinonasal SCC and ITAC may benefit from therapy with immune checkpoint inhibitors that recently have been approved for clinical application in head and neck cancer.

Immunotherapy in head and neck cancer: evidence and perspectives

Head and neck squamous cell carcinomas evade immune response through multiple immunologic resistance mechanisms. Two of the most commonly involved checkpoint inhibitory mechanisms are CTLA-4 and PD-1/PD-L1, which act at earlier and later stages of immune response to tumors. Pembrolizumab and nivolumab are PD-1 antibodies that interrupt the immunosuppressive pathway of inhibitory checkpoints, which are used by tumor cells to prevent immune reaction. Both recently gained US FDA approval for the treatment of patients with recurrent or metastatic head and neck cancer with disease progression during or following platinum containing chemotherapy. No conclusions can be drawn on the role of PD-L1 in identifying patients responding to immunotherapy, given that similar studies lead to contrasting results. It will be crucial to identify predictive markers of immunotherapy response, and to evaluate them prospectively. A better understanding of the complex network between tumor, immune system and other oncologic treatments will help us to develop more efficient multimodality treatments.

Assessing Tumor-Infiltrating Lymphocytes in Solid Tumors: A Practical Review for Pathologists and Proposal for a Standardized Method from the International Immuno-Oncology Biomarkers Working Group: Part 2: TILs in Melanoma, Gastrointestinal Tract Carcinomas, Non-Small Cell Lung Carcinoma and Mesothelioma, Endometrial and Ovarian Carcinomas, Squamous Cell Carcinoma of the Head and Neck, Genitourinary Carcinomas, and Primary Brain Tumors

Assessment of the immune response to tumors is growing in importance as the prognostic implications of this response are increasingly recognized, and as immunotherapies are evaluated and implemented in different tumor types. However, many different approaches can be used to assess and describe the immune response, which limits efforts at implementation as a routine clinical biomarker. In part 1 of this review, we have proposed a standardized methodology to assess tumor-infiltrating lymphocytes (TILs) in solid tumors, based on the International Immuno-Oncology Biomarkers Working Group guidelines for invasive breast carcinoma. In part 2 of this review, we discuss the available evidence for the prognostic and predictive value of TILs in common solid tumors, including carcinomas of the lung, gastrointestinal tract, genitourinary system, gynecologic system, and head and neck, as well as primary brain tumors, mesothelioma and melanoma. The particularities and different emphases in TIL assessment in different tumor types are discussed. The standardized methodology we propose can be adapted to different tumor types and may be used as a standard against which other approaches can be compared. Standardization of TIL assessment will help clinicians, researchers and pathologists to conclusively evaluate the utility of this simple biomarker in the current era of immunotherapy.

Identification of molecular targets in vulvar cancers

OBJECTIVES

To identify molecular alterations that contribute to vulvar cancer pathogenesis with the intent of identifying molecular targets for treatment.

METHODS

After retrospective analysis of a database of molecularly-profiled gynecologic cancer patients, 149 vulvar cancer patients were included and tested centrally at a CLIA laboratory (Caris Life Sciences, Phoenix, AZ). Tests included one or more of the following: gene sequencing (Sanger or next generation sequencing [NGS]), protein expression (immunohistochemistry [IHC]), and gene amplification (C/FISH). A Fisher's exact test was used when indicated with a p-value≤0.05 indicating significance.

RESULTS

Median age was 65. 85% had squamous cell carcinoma (SCC) and 15% adenocarcinoma (ADC) histologies. 46% had metastatic (Stage IV) disease. Targeted hot-spot sequencing identified variants in the following genes: TP53 (33%), PIK3CA/BRCA2 (8%, 10%, respectively), HRAS/FBXW7 (5%, 4%, respectively) and ERBB4/GNAS (3%, 3% respectively). Mutations in AKT1, ATM, FGFR2, KRAS, NRAS (n=1, respectively) and BRAF (n=2) also occurred. Specific protein changes for targetable genes included clinically pathogenic mutations commonly found in other cancers (e.g. PIK3CA: exon 9 [E545K], RAS: G13D, Q61L, BRCA2: S1667X, BRAF: R443T, FBXW7: E471fs, etc.). Drug targets identified by IHC and ISH methodologies include cMET (32% IHC, 2% ISH), PDL1 (18%), PTEN loss (56%), HER2 (4% IHC, 2% ISH) and hormone receptors (AR, 4%; ER, 11%; PR, 4%). Comparisons between SCC and ADC identified differential rates for AR, ER, HER2 and GNAS with an increased presence in ADC (p-values all <0.05).

CONCLUSIONS

Molecularly-guided precision medicine could provide vulvar cancer patients alternative, targeted treatment options.

Precision Medicine: Genomic Profiles to Individualize Therapy

Precision medicine is the application of genotypic and Omics biomarkers to determine the most appropriate, outcome-driven therapy for individual patients. To determine the best choice of therapy, institutions use significant information technology-enabled data from imaging, electronic medical records, sensors in the clinic/hospitals, and wearable sensors to determine treatment response. With genomic profiling, targets to affect a disease course are continuing to be developed. As clonal mutational prevalence continues to be understood, information can be communicated to patients to inform them that resistance is common, requiring collection of more genetic mutations from patients with further biopsies or blood collection.

Elevated frequencies of CD8 T cells expressing PD-1, CTLA-4 and Tim-3 within tumour from perineural squamous cell carcinoma patients

Perineural spread of tumour cells along cranial nerves is a severe complication of primary cutaneous squamous cell carcinomas of the head and neck region. While surgical excision of the tumour is the treatment of choice, removal of all the tumour is often complicated by the neural location and recurrence is frequent. Non-invasive immune treatments such as checkpoint inhibitor blockade may be useful in this set of tumours although little is understood about the immune response to perineural spread of squamous cell carcinomas. Immunohistochemistry studies suggest that perineural tumour contains a lymphocyte infiltrate but it is difficult to quantitate the different proportions of immune cell subsets and expression of checkpoint molecules such as PD-1, Tim-3 and CTLA-4. Using flow cytometry of excised perineural tumour tissue, we show that a T cell infiltrate is prominent in addition to less frequent B cell, NK cell and NKT cell infiltrates. CD8 T cells are more frequent than other T cells in the tumour tissue. Amongst CD8 T cells, the frequency of Tim-3, CTLA-4 and PD-1 expressing cells was significantly greater in the tumour relative to the blood, a pattern that was repeated for Tim-3, CTLA-4 and PD-1 amongst non-CD8 T cells. Using immunohistochemistry, PD-1 and PD-L1-expression could be detected in close proximity amongst perineural tumour tissue. The data suggest that perineural SCC contains a mixture of immune cells with a predominant T cell infiltrate containing CD8 T cells. Elevated frequencies of tumour-associated Tim-3⁺, CTLA-4⁺ and PD-1⁺ CD8 T cells suggests that a subset of patients may benefit from local antibody blockade of these checkpoint inhibitors.

Differentiated State of Initiating Tumor Cells Is Key to Distinctive Immune Responses Seen in H-RasG12V-Induced Squamous Tumors

Heterogeneity in tumor immune responses is a poorly understood yet critical parameter for successful immunotherapy. In two doxycycline-inducible models where oncogenic H-Ras^G12V is targeted either to the epidermal basal/stem cell layer with a Keratin14-rtTA transgene (K14Ras), or committed progenitor/suprabasal cells with an Involucrin-tTA transgene (InvRas), we observed strikingly distinct tumor immune responses. On threshold doxycycline levels yielding similar Ras expression, tumor latency, and numbers, tumors from K14Ras mice had an immunosuppressed microenvironment, whereas InvRas tumors had a proinflammatory microenvironment. On a Rag1^-/- background, InvRas mice developed fewer and smaller tumors that regressed over time, whereas K14Ras mice developed more tumors with shorter latency than Rag1^+/+ controls. Adoptive transfer and depletion studies revealed that B-cell and CD4 T-cell cooperation was critical for tumor yield, lymphocyte polarization, and tumor immune phenotype in Rag1^+/+ mice of both models. Coculture of tumor-conditioned B cells with CD4 T cells implicated direct contact for Th1 and regulatory T cell (Treg) polarization, and CD40-CD40L for Th1, Th2, and Treg generation, a response not observed from splenic B cells. Anti-CD40L caused regression of InvRas tumors but enhanced growth in K14Ras, whereas a CD40 agonist mAb had opposite effects in each tumor model. These data show that position of tumor-initiating cells within a stratified squamous epithelial tissue provokes distinct B- and CD4 T-cell interactions, which establish unique tumor microenvironments that regulate tumor development and response to immunotherapy. Cancer Immunol Res; 5(3); 198-210. ©2017 AACR.