B cell regulation of the anti-tumor response and role in carcinogenesis

Rituximab as a therapeutic option for patients with advanced melanoma

Treatment of metastatic melanoma remains challenging, despite a variety of new and promising immunotherapeutic and targeted approaches to therapy. New treatment options are still needed to improve long-term tumour control. We present a case series of seven patients with metastatic melanoma who were treated individually with the anti-CD20 antibody rituximab between July 2014 and July 2015. Two of the patients were treated in an adjuvant setting. All patients had already received a variety of treatments. During an induction phase, the administration of four cycles of weekly rituximab 375 mg/m2 body surface area was planned. After imaging, patients with stable disease continued therapy with rituximab 375 mg/m2 body surface area every 4 weeks up to a maximum of 24 weeks. Two patients experienced grade 2 infusion reactions during the first infusion. Otherwise, treatment was well tolerated and there were no grade 3 or 4 side effects. Staging after the induction phase showed stable disease in five patients, and two patients had progressive disease. Median progression-free survival was 6.3 months (95% CI 4.97-7.53), median overall survival was 14.7 months (95% CI 4.52-24.94), and one patient was still alive in December 2016. In conclusion, rituximab might be a therapeutic option for metastatic melanoma. However, further studies on rituximab among larger patient cohorts are warranted. Evaluation of therapy in an adjuvant setting or in combination with other systemic treatment might, therefore, be of particular interest.

High Densities of Tumor-Associated Plasma Cells Predict Improved Prognosis in Triple Negative Breast Cancer

Breast cancer is the most common malignancy affecting women, but the heterogeneity of the condition is a significant obstacle to effective treatment. Triple negative breast cancers (TNBCs) do not express HER2 or the receptors for estrogen or progesterone, and so often have a poor prognosis. Tumor-infiltrating T cells have been well-characterized in TNBC, and increased numbers are associated with better outcomes; however, the potential roles of B cells and plasma cells have been large. Here, we conducted a retrospective correlative study on the expression of B cell/plasma cell-related genes, and the abundance and localization of B cells and plasma cells within TNBCs, and clinical outcome. We analyzed 269 TNBC samples and used immunohistochemistry to quantify tumor-infiltrating B cells and plasma cells, coupled with NanoString measurement of expression of immunoglobulin metagenes. Multivariate analysis revealed that patients bearing TNBCs with above-median densities of CD38⁺ plasma cells had significantly better disease-free survival (DFS) (HR = 0.44; 95% CI 0.26–0.77; p = 0.004) but not overall survival (OS), after adjusting for the effects of known prognostic factors. In contrast, TNBCs with higher immunoglobulin gene expression exhibited improved prognosis (OS p = 0.029 and DFS p = 0.005). The presence of B cells and plasma cells was positively correlated (p < 0.0001, R = 0.558), while immunoglobulin gene IGKC, IGHM, and IGHG1 mRNA expression correlated specifically with the density of CD38⁺ plasma cells (IGKC p < 0.0001, R = 0.647; IGHM p < 0.0001, R = 0.580; IGHG1 p < 0.0001, R = 0.655). Interestingly, after adjusting the multivariate analysis for the effect of intratumoral CD38⁺ plasma cell density, the expression levels of all three genes lost significant prognostic value, suggesting a biologically important role of plasma cells. Last but not least, the addition of intratumoral CD38⁺ plasma cell density to clinicopathological features significantly increased the prognostic value for both DFS (ΔLRχ² = 17.28, p = 1.71E−08) and OS (ΔLRχ² = 10.03, p = 6.32E−08), compared to clinicopathological features alone. The best combination was achieved by integrating intratumoral CD38⁺ plasma cell density and IGHG1 which conferred the best added prognostic value for DFS (ΔLRχ² = 27.38, p = 5.22E−10) and OS (ΔLRχ² = 21.29, p = 1.03E−08). Our results demonstrate that the role of plasma cells in TNBC warrants further study to elucidate the relationship between their infiltration of tumors and disease recurrence.

Subsite heterogeneity in the profiles of circulating cytokines in colorectal cancer

Colorectal cancers (CRCs) are treated as one entity but are in fact a heterogeneous group of diseases. If not addressed, subsite-associated variability may interfere with mechanism-targeted therapies and accuracy of potential CRC biomarkers. Little is known about the contribution of systemic inflammatory and immune mediators to subsite heterogeneity in CRC. Our purpose was to compare the profiles of key cytokines between right and left colonic and rectal CRCs. Using Luminex xMAP® technology, serum concentrations of eotaxin, IL-1β, IL-1ra, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, IL-12(p70), IL-13, IL-15, IL-17, IFNγ, IP-10, FGF-2, G-CSF, GM-CSF, MCP-1, MIP-1α and β, PDGF-BB, RANTES, TNFα, and VEGF-A were determined in 104 CRC patients. We found the concentrations of IL-12(p70), IL-10, IL-1ra, IL-4, IL-6, IL-7, IL-8, G-CSF and TNFα to be significantly higher in right-sided and GM-CSF in left-sided than rectal CRCs. The concentrations of IFNγ and MIP-1α were significantly higher in right-sided CRCs as compared to cancers of other locations combined. In turn, MIP-1β was higher in rectal CRCs as compared to colon cancers. Taken together, our results show subsite heterogeneity of CRC cancers in terms of systemic inflammatory and immune responses that ought to be taken into account when attempting immunotherapy or developing biomarkers. Additionally, more pronounced T_H2 response accompanied by T_H1 immunity and more prominent tumor-promoting inflammation in CRC patients with primary tumors originating from right-sided colon may constitute a molecular background of unfavorable prognosis associated with this location.

Tumor-infiltrating B cells: their role and application in anti-tumor immunity in lung cancer

Evidence indicates that lung cancer development is a complex process that involves interactions between tumor cells, stromal fibroblasts, and immune cells. Tumor-infiltrating immune cells play a significant role in the promotion or inhibition of tumor growth. As an integral component of the tumor microenvironment, tumor-infiltrating B lymphocytes (TIBs) exist in all stages of cancer and play important roles in shaping tumor development. Here, we review recent clinical and preclinical studies that outline the role of TIBs in lung cancer development, assess their prognostic significance, and explore the potential benefit of B cell-based immunotherapy for lung cancer treatment.

Growth and Immune Evasion of Lymph Node Metastasis

Cancer patients with lymph node (LN) metastases have a worse prognosis than those without nodal disease. However, why LN metastases correlate with reduced patient survival is poorly understood. Recent findings provide insight into mechanisms underlying tumor growth in LNs. Tumor cells and their secreted molecules engage stromal, myeloid, and lymphoid cells within primary tumors and in the lymphatic system, decreasing antitumor immunity and promoting tumor growth. Understanding the mechanisms of cancer survival and growth in LNs is key to designing effective therapy for the eradication of LN metastases. In addition, uncovering the implications of LN metastasis for systemic tumor burden will inform treatment decisions. In this review, we discuss the current knowledge of the seeding, growth, and further dissemination of LN metastases.

The good, the (not so) bad and the ugly of immune homeostasis in melanoma

Within the immune system multiple mechanisms balance the need for efficient pathogen recognition and destruction with the prevention of tissue damage by excessive, inappropriate or even self-targeting (auto)immune reactions. This immune homeostasis is a tightly regulated system which fails during tumor development, often due to the hijacking of its essential self-regulatory mechanisms by cancer cells. It is facilitated not only by tumor intrinsic properties, but also by the microbiome, host genetics and other factors. In certain ways many cancers can therefore be considered a rare failure of immune control rather than an uncommon or rare disease of the tissue of origin, as the acquisition of potentially oncogenic traits through mutation occurs constantly in most tissues during proliferation. Normally, aberrant cells are well-controlled by cell intrinsic (repair or apoptosis) and extrinsic (immune) mechanisms. However, occasionally oncogenic cells survive and escape control. Melanoma is one of the first cancer types where treatments aimed at restoring and enhancing an immune response to regain control over the tumor have been used with various success rates. With the advent of "modern" immunotherapeutics such as anti-CTLA-4 or anti-PD-1 antibodies that both target negative immune-regulatory pathways on immune cells resulting in durable responses in a proportion of patients, the importance of the interplay between the immune system and cancer has been established beyond doubt.

Immune Cell Infiltration and Tertiary Lymphoid Structures as Determinants of Antitumor Immunity

Limited representation of intratumoral immune cells is a major barrier to tumor control. However, simply enhancing immune responses in tumor-draining lymph nodes or through adoptive transfer may not overcome the limited ability of tumor vasculature to support effector infiltration. An alternative is to promote a sustained immune response intratumorally. This idea has gained traction with the observation that many tumors are associated with tertiary lymphoid structures (TLS), which organizationally resemble lymph nodes. These peri- and intratumoral structures are usually, but not always, associated with positive prognoses in patients. Preclinical and clinical data support a role for TLS in modulating immunity in the tumor microenvironment. However, there appear to be varied functions of TLS, potentially based on their structure or location in relation to the tumor or the origin or location of the tumor itself. Understanding more about TLS development, composition, and function may offer new therapeutic opportunities to modulate antitumor immunity.

CD21lo/medCD27+ proinflammatory B cells are enriched in breast cancer patients and promote antitumor T cell responses

Breast cancer is a common malignancy and a major cause of death in women worldwide. The immunomodulatory role of B cells is being increasingly recognized in autoimmune diseases and cancers. In recent years, immunotherapeutic strategies that upregulate the patient's own antitumor T cell responses have shown promise in treating solid tumors and are being developed for breast cancer. In this study, we discovered that the B cells in breast cancer patients were enriched with interferon (IFN)-γ-expressing cells and presented high potency for IFN-γ production. These IFN-γ-expressing B cells were enriched in, but did not completely overlap with, the CD21^lo/medCD27⁺IgM^-IgD^-IgG⁺IgA^- B cell subset, which was consistent with IgG-expressing memory B cells. Compared to CD27⁺IgG^- B cells, the CD27⁺IgG⁺ B cells expressed significantly higher IFN-γ expression. Given that B cells demonstrate important antigen-presenting function to T cells, we incubated CD27⁺IgG^- B cells and CD27⁺IgG⁺ B cells with autologous CD4⁺ T cells. Compared to the CD4⁺ T cells that were incubated with CD27⁺IgG^- B cells, the CD4⁺ T cells that were incubated with CD27⁺IgG⁺ B cells presented significantly higher TBX21 and lower FOXP3 expression, suggesting that the CD27⁺IgG⁺ B cells, but not the CD27⁺IgG^- B cells, promoted Th1 and suppressed regulatory T cell responses. IFN-γ-expressing B cells were further enriched in the intratumoral environment of breast cancer patients. Together, we discovered that breast cancer patients presented an upregulation of IFN-γ-expressing proinflammatory B cells with the potency to promote Th1 responses.

Parity History Determines a Systemic Inflammatory Response to Spread of Ovarian Cancer in Naturally Aged Mice

Aging intersects with reproductive senescence in women by promoting a systemic low-grade chronic inflammation that predisposes women to several diseases including ovarian cancer (OC). OC risk at menopause is significantly modified by parity records during prior fertile life. To date, the combined effects of age and parity on the systemic inflammation markers that are particularly relevant to OC initiation and progression at menopause remain largely unknown. Herein, we profiled a panel of circulating cytokines in multiparous versus virgin C57BL/6 female mice at peri-estropausal age and investigated how cytokine levels were modulated by intraperitoneal tumor induction in a syngeneic immunocompetent OC mouse model. Serum FSH, LH and TSH levels increased with age in both groups while prolactin (PRL) was lower in multiparous respect to virgin mice, a finding previously observed in parous women. Serum CCL2, IL-10, IL-5, IL-4, TNF-α, IL1-β and IL-12p70 levels increased with age irrespective of parity status, but were specifically reduced following OC tumor induction only in multiparous mice. Animals developed hemorrhagic ascites and tumor implants in the omental fat band and other intraperitoneal organs by 12 weeks after induction, with multiparous mice showing a significantly extended survival. We conclude that previous parity history counteracts aging-associated systemic inflammation possibly by reducing the immunosuppression that typically allows tumor spread. Results suggest a partial impairment of the M2 shift in tumor-associated macrophages as well as decreased stimulation of regulatory B-cells in aged mice. This long term, tumor-concurrent effect of parity on inflammation markers at menopause would be a contributing factor leading to decreased OC risk.

The emerging role of anti-CD25 directed therapies as both immune modulators and targeted agents in cancer

CD25 (also termed IL2RA) forms one component of the high-affinity heterotrimeric interleukin 2 (IL2) receptor on activated T cells. Its affinity for IL2 and cellular function are tightly regulated and vary in different cell types. The high frequency of CD25 on the surface of many different haematological tumour cells is now well established and, apart from its prognostic significance, CD25 may be present on leukaemic stem cells and enable oncogenic signalling pathways in leukaemic cells. Additionally, high CD25 expression in activated circulating immune cells and Tregs is a factor that has already been exploited by IL2 immunotherapies for treatment of tumours and autoimmune disease. The relative clinical safety and efficacy of administering anti-CD25 radioimmunoconjugates and immunotoxins in various haematological tumour indications has been established and clinical trials of a novel CD25-directed antibody drug conjugate are underway.

Tumor-associated immune aggregates in oral cancer: Their cellular composition and potential prognostic significance

There is growing evidence supporting the importance of immune microenvironment in cancer development and progression, especially with the rapid development of immunotherapy. Presence of immune cell aggregates in solid tumors has been associated with clinical outcomes, but little is known about the immune microenvironment in oral squamous cell carcinoma (OSCC), which has high morbidity and mortality. Based on our preliminary observation, we hypothesize that there is the presence of tumor-associated immune aggregates (TaIAs) during oral cancer development. Adapting to the dynamic change of the composition of cellular membership and co-evolving with the tumor at invasion fronts, these TaIAs, either pro-inflammatory or immune suppressive, are associated with clinical consequences. With the unique access to a set of prospectively collected, highly annotated OSCC surgical samples and the use of multi-color immunostaining of key immune cells, the confirmation of our hypothesis may shed light of the underlying biology related to OSCC and the knowledge learned can potentially be used to identify prognostic markers, response predictive markers for immunotherapies, as well as novel therapeutic targets.

Immunotherapy of WAP-TNP mice with early stage mammary gland tumors

The SV40 transgenic BALB/c mouse based WAP-T/WAP-T_NP model for triple-negative breast cancer allows the analysis of parameters influencing immunotherapeutic approaches. Except for WAP-T_NP tumors expressing the immune-dominant LCMV NP-epitope within SV40 T-antigen (T-Ag_NP) which is not expressed by T-Ag of WAP-T tumors, the tumors are extremely similar. Comparative anti-PD1/PD-L1 immunotherapy of WAP-T and WAP-T_NP mice supported the hypothesis that the immunogenicity of tumor antigen T-cell epitopes strongly influences the success of immune checkpoint blockade therapy, with highly immunogenic T-cell epitopes favoring rapid CTL exhaustion. Here we analyzed the immune response in NP8 mice during early times of tumor development. LCMV infection of lactating NP8 mice induced lifelong tumor protection by memory CTLs. Immunization with LCMV after involution and appearance of T-Ag_NP expressing parity-induced tumor progenitor cells could not cure the mice, as memory CTLs became exhausted. However, immunization significantly prolonged the time of tumor outgrowth. Elimination of exhausted CTLs and of immunosuppressive cells by sub-lethal γ-irradiation, followed by adoptive transfer of NP-epitope specific CTLs into NP8 tumor mice with early lesions, completely prevented tumor outgrowth, when lymphocytes obtained after injection of weakly immunogenic NP8 tumor-derived cells into BALB/c mice were transferred. Transfer of lymphocytes obtained after infection of BALB/c mice with highly immunogenic LCMV into such mice delayed tumor outgrowth for a significant period, but could not prevent it. We conclude that eliminating exhausted CTLs and immune-suppressive cells followed by transfer or generation of low-avidity tumor antigen-specific CTLs might be a promising approach for curative tumor immunotherapy.

Leukocyte trafficking in tumor microenvironment

The tumor microenvironment consists of both malignant and non-malignant cells and a plethora of soluble mediators. Different types of tumors have specific tumor microenvironments characterized by distinct chemokines and chemotactic factors that influence leukocyte recruitment. The immune cell infiltrate continuously interacts with stroma cells and influence tumor growth. Emerging evidence suggests that the regulation of the composition and the metabolic state of tumor-associated leukocytes may represent a new promising intervention strategy. Here we summarize the current knowledge on the role of tumor-associated immune cells in tumor growth and dissemination, with a specific focus on the nature of the chemotactic factors responsible for their accumulation and activation in tumors.

Colorectal tumors are enriched with regulatory plasmablasts with capacity in suppressing T cell inflammation

Inflammation plays a critical role in the initiation of colorectal cancer but is also required to mediate antitumor immunity in established tumors. Therefore, identifying the cellular and molecular components in colorectal tumors is necessary for the understanding of tumor progression and the development of novel treatment strategies. In this study, we demonstrated that a specific subtype of regulatory B cells, the CD19^loCD27^hi plasmablasts, was enriched in the colorectal tumor microenvironment. This CD19^loCD27^hi plasmablast subset presented high interleukin 10 (IL-10) expression but not transforming growth factor-β (TGF-β) secretion. Phenotypically, the tumor-infiltrating IL-10⁺ CD19^loCD27^hi plasmablasts presented lower CD24, CD38, and IgA, and higher Tim-1 and IgG expression compared to the IL-10^- CD19^loCD27^hi plasmablasts. The tumor-infiltrating IL-10⁺ CD19^loCD27^hi plasmablasts were found to be gut-homing due to their higher expression of α4β7 while peripheral blood B cells did not show the same characteristic. When cocultured with autologous T cells, CD19^loCD27^hi plasmablasts demonstrated potent activity in suppressing interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) expression but did not promote Foxp3 expression. Overall, this study demonstrate that in colorectal cancer, CD19^loCD27^hi plasmablasts make up a large percentage in tumor-infiltrating lymphocytes and possess potent immunoregulatory functions, and thus could be utilized in future therapeutic strategies.

Novel genetic locus at MHC region for esophageal squamous cell carcinoma in Chinese populations

Background

Our previous genome-wide association study (GWAS) identified three independent single nucleotide polymorphisms (SNPs) in human major histocompatibility complex (MHC) region showing association with esophageal squamous cell carcinoma (ESCC). In this study, we increased GWAS sample size on MHC region and performed validation in an independent ESCC cases and normal controls with aim to find additional loci at MHC region showing association with an increased risk to ESCC.

Methods

The 1,077 ESCC cases and 1,733 controls were genotyped using Illumina Human 610-Quad Bead Chip, and 451 cases and 374 controls were genotyped using Illumina Human 660W-Quad Bead Chip. After quality control, the selected SNPs were replicated by TaqMan genotyping assay on another 2,026 ESCC cases and 2,384 normal controls.

Results

By excluding low quality SNPs in primary GWAS screening, we selected 2,533 SNPs in MHC region for association analysis, and identified 5 SNPs with p <10⁻⁴. Further validation analysis in an independent case-control cohort confirmed one of the 5 SNPs (rs911178) that showed significant association with ESCC. rs911178 (P_GWAS = 6.125E-04, OR = 0.644 and P_replication = 1.406E-22, OR = 0.489) was located at upstream of SCAND3.

Conclusion

The rs911178 (SCAND3 gene) in MHC region is significantly associated with high risk of ESCC. This study not only reveal the potential role of MHC region for the pathogenesis of ESCC, but also provides important clues for the establishment of tools and methods for screening high risk population of ESCC.

Single-cell RNA-seq enables comprehensive tumour and immune cell profiling in primary breast cancer

Single-cell transcriptome profiling of tumour tissue isolates allows the characterization of heterogeneous tumour cells along with neighbouring stromal and immune cells. Here we adopt this powerful approach to breast cancer and analyse 515 cells from 11 patients. Inferred copy number variations from the single-cell RNA-seq data separate carcinoma cells from non-cancer cells. At a single-cell resolution, carcinoma cells display common signatures within the tumour as well as intratumoral heterogeneity regarding breast cancer subtype and crucial cancer-related pathways. Most of the non-cancer cells are immune cells, with three distinct clusters of T lymphocytes, B lymphocytes and macrophages. T lymphocytes and macrophages both display immunosuppressive characteristics: T cells with a regulatory or an exhausted phenotype and macrophages with an M2 phenotype. These results illustrate that the breast cancer transcriptome has a wide range of intratumoral heterogeneity, which is shaped by the tumour cells and immune cells in the surrounding microenvironment.

Genetic heterogeneity in breast cancer has been demonstrated at a single-cell resolution with high levels of genome coverage. Here, the authors perform transcriptome analysis of 515 single cells from 11 patients and define core gene expression signatures for subtype-specific single breast cancer cells and tumour-infiltrating immune cells.

Obstacles Posed by the Tumor Microenvironment to T cell Activity: A Case for Synergistic Therapies

T cell dysfunction in solid tumors results from multiple mechanisms. Altered signaling pathways in tumor cells help produce a suppressive tumor microenvironment enriched for inhibitory cells, posing a major obstacle for cancer immunity. Metabolic constraints to cell function and survival shape tumor progression and immune cell function. In the face of persistent antigen, chronic T cell receptor signaling drives T lymphocytes to a functionally exhausted state. Here we discuss how the tumor and its microenvironment influences T cell trafficking and function with a focus on melanoma, and pancreatic and ovarian cancer, and discuss how scientific advances may help overcome these hurdles.

Detailed resolution analysis reveals spatial T cell heterogeneity in the invasive margin of colorectal cancer liver metastases associated with improved survival

On a broader scale, T cell density and localization in colorectal cancer liver metastases have prognostic and predictive implications. As T cell distribution at higher resolutions has not been fully investigated, a detailed resolution analysis of T cell distribution was performed. Patient tissues were divided into 10 µm distance classes between the tumor border and adjacent normal liver. Thereby, distinct density patterns of T cell localization in relation to the malignant tissue could be detected. At a distance of 20 to 30 µm to the tumor, a decrease of CD3 T cells is common. Within this area, cytotoxic Granzyme B and CD8⁺ T cells were found to be significantly reduced as well as CD163 macrophages were increased and identified to be in close contact with T cells. Our data suggests a physical or functional border within this region. Survival analysis revealed improved overall survival in patients with high T cells numbers at the direct tumor border. Interestingly, the decreased T cells in the 20 to 30 µm region were also found to be significantly associated with improved survival. Consequently, the detailed localization of T cells, despite blockade, could be associated with improved clinical outcome. The high-resolution analysis represents new insights into relevant heterogenous T cell distributions especially related to clinical responses. As the paradoxical observation of localization-dependent prognostic relevance of T cell densities is only detectable by detailed spatial analyses, this investigation of spatial profiles at higher resolutions is suggested as a new biomarker for survival and response to therapies.

Macrophage regulation of B cell proliferation

Unlike organized lymphoid tissue, the tumor microenvironment (TME) often includes a high proportion of immunosuppressive macrophages. We model the TME by culturing peritoneal cavity (PerC) cells that naturally have a high macrophage to lymphocyte ratio. Prior studies revealed that, following TCR ligation, PerC T cell proliferation is suppressed due to IFNγ-triggered inducible nitric oxide synthase expression. In this study we assessed the ability of PerC B cells to respond to surrogate activating signals in the presence of high numbers of macrophages. Surface IgM (BCR) ligation led to cyclooxygenase-mediated, and TLR-4 ligation to IL10-mediated, suppression of PerC B cell proliferation. In contrast, PerC B cells had a robust response to CD40 ligation, which could overcome the suppression generated by the BCR or TLR-4 response. However, the CD40 response was suppressed by concurrent TCR ligation. These results reveal the challenges of promoting B and T cell responses in macrophage-rich conditions that model the TME.

Challenges and opportunities for checkpoint blockade in T-cell lymphoproliferative disorders

The T-cell lymphoproliferative disorders are a heterogeneous group of non-Hodgkin’s lymphomas (NHL) for which current therapeutic strategies are inadequate, as most patients afflicted with these NHL will succumb to disease progression within 2 years of diagnosis. Appreciation of the genetic and immunologic landscape of these aggressive NHL, including PD-L1 (B7-H1, CD274) expression by malignant T cells and within the tumor microenvironment, provides a strong rationale for therapeutic targeting this immune checkpoint. While further studies are needed, the available data suggests that responses with PD-1 checkpoint blockade alone will unlikely approach those achieved in other lymphoproliferative disorders. Herein, we review the unique challenges posed by the T-cell lymphoproliferative disorders and discuss potential strategies to optimize checkpoint blockade in these T-cell derived malignancies.

CD40L confers helper functions to human intra-melanoma class-I-restricted CD4+CD8+ double positive T cells

Although CD4⁺CD8⁺ double positive (DP) T cells represent a small fraction of peripheral T lymphocytes in healthy human donors, their frequency is often increased under pathological conditions (in blood and targeted tissues). In solid cancers such as melanoma, we previously demonstrated an enrichment of tumor reactive CD4^lowCD8^highαβ DP T cells among tumor-infiltrating lymphocytes of unknown function. Similarly to their single positive (SP) CD8⁺ counterparts, intra-melanoma DP T cells recognized melanoma cell lines in an HLA-class-I restricted context. However, they presented a poor cytotoxic activity but a strong production of diverse Th1 and Th2 cytokines. The aim of this study was to clearly define the role of intra-melanoma CD4^lowCD8^highαβ DP T cells in the antitumor immune response. Based on a comparative transcriptome analysis between intra-melanoma SP CD4⁺, SP CD8⁺ and DP autologous melanoma-infiltrating T-cell compartments, we evidenced an overexpression of the CD40L co-stimulatory molecule on activated DP T cells. We showed that, like SP CD4⁺ T cells, and through CD40L involvement, DP T cells are able to induce both proliferation and differentiation of B lymphocytes and maturation of functional DCs able to efficiently prime cytotoxic melanoma-specific CD8 T-cell responses. Taken together, these results highlight the helper potential of atypical DP T cells and their role in potentiating antitumor response.