Melanomas resist T-cell therapy through inflammation-induced reversible dedifferentiation

Abstract

Adoptive cell transfer therapies (ACTs) with cytotoxic T cells that target melanocytic antigens can achieve remissions in patients with metastatic melanomas, but tumours frequently relapse. Hypotheses explaining the acquired resistance to ACTs include the selection of antigen-deficient tumour cell variants and the induction of T-cell tolerance. However, the lack of appropriate experimental melanoma models has so far impeded clear insights into the underlying mechanisms. Here we establish an effective ACT protocol in a genetically engineered mouse melanoma model that recapitulates tumour regression, remission and relapse as seen in patients. We report the unexpected observation that melanomas acquire ACT resistance through an inflammation-induced reversible loss of melanocytic antigens. In serial transplantation experiments, melanoma cells switch between a differentiated and a dedifferentiated phenotype in response to T-cell-driven inflammatory stimuli. We identified the proinflammatory cytokine tumour necrosis factor (TNF)-α as a crucial factor that directly caused reversible dedifferentiation of mouse and human melanoma cells. Tumour cells exposed to TNF-α were poorly recognized by T cells specific for melanocytic antigens, whereas recognition by T cells specific for non-melanocytic antigens was unaffected or even increased. Our results demonstrate that the phenotypic plasticity of melanoma cells in an inflammatory microenvironment contributes to tumour relapse after initially successful T-cell immunotherapy. On the basis of our work, we propose that future ACT protocols should simultaneously target melanocytic and non-melanocytic antigens to ensure broad recognition of both differentiated and dedifferentiated melanoma cells, and include strategies to sustain T-cell effector functions by blocking immune-inhibitory mechanisms in the tumour microenvironment.

Targeting TNF alpha as a novel strategy to enhance CD8+T cell-dependent immune response in melanoma?

“…2 In addition, TNF triggered melanoma dedifferentiation, promoting melanoma relapse in an adoptive CD8+ T cell transfer protocol. 3 We have recently demonstrated that TNF signaling facilitates the tumor growth of mouse melanoma exhibiting a high-expression level of major histocompatibility class I (MHC-I high ), while having no or minimal effects toward mouse melanoma expressing MHC-I at low levels (MHC-I low ). As a matter of fact, we provided evidence that the tumor growth of MHC-I high , but not that of MHC-I low melanoma, was impaired in TNF-deficient mice.…”

Against Organizational Functions

“…These barriers include apoptosis and immune recognition. Tumors can also change their protein expression patterns in the course of immune therapy in such a way as to increase their resistance to such therapies (Landsberg et al 2012). As cancer researchers Gatenby and Gillies (2008, 56) recently put it, "Somatic evolution of invasive cancer can …be viewed as a sequence of phenotypical adaptations to these barriers.…”

In situloading of skin dendritic cells with apoptotic bleb-derived antigens for the induction of tumor-directed immunity

“…C and CD8 C T-cell proliferation (n D 7). (B) DCs that egressed from the skin biopsies after injecting either wild-type or MART-1 expressing apoptotic cell remnants (ACRs) or blebs, were co-cultured with a MART-1 [26][27][28][29][30][31][32][33][34][35] recognizing and HLA-A2 restricted cytotoxic T lymphocyte (CTL) line (> 95% pure) for 24 hours. Antigen-specific activation was determined by deducting the levels of interferon g (IFNg) produced following the injection of wild-type ACRs or blebs from the levels produced after injecting MART-1 expressing apoptotic fractions (n D 3).…”

“…injected in skin explants from HLA-A2 positive donors in the presence of 4/GM, and skin DC were harvested after 48-72 hours. After a subsequent 24 hours of co-culture with a MART-1 [26][27][28][29][30][31][32][33][34][35] recognizing CTL line (HLA-A2 restricted; >95% pure), the supernatant was analyzed for the presence of IFNg, as a measure of cross-presentation of the MART-1 [26][27][28][29][30][31][32][33][34][35] epitope by egressed DC. The MART-1 [26][27][28][29][30][31][32][33][34][35] specific IFNg production was assessed by deducting the IFNg production following a co-culture with DC from wild-type ACR or blebs injected skin, from that secreted after co-culturing with DC from MART-1-transduced ACR or blebs (D IFNg, Fig.…”

“…injection should be selected to preferentially target CD1a C CD14 ¡ DDCs as these represent the most frequent skin DC subset with superior T-cell activation qualities, and as such, are thus likely to be the most potent in inducing tumor-specific T-cell responses. 1,12,13 Malignant cells have multiple ways of evading immune recognition, one of which is de-differentiation, 14 often accompanied by a loss of TAA expression, suggesting that broadening the tumordirected immune response by increasing the array of presented TAAa is likely to enhance the effectiveness of antitumor vaccination strategies. Most immunotherapeutic strategies that target a single TAA, rely on the characterization of the selected TAA, have limited inter-patient antigenic overlap and are often HLArestricted.…”