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Epithelial-to-mesenchymal transition (EMT)-inducing transcription factors (TF) are well known for their ability to induce mesenchymal states associated with increased migratory and invasive properties. Unexpectedly, nuclear expression of the EMT-TF ZEB2 in human primary melanoma has been shown to correlate with reduced invasion. We report here that ZEB2 is required for outgrowth for primary melanomas and metastases at secondary sites. Ablation of Zeb2 hampered outgrowth of primary melanomas in vivo, whereas ectopic expression enhanced proliferation and growth at both primary and secondary sites. Gain of Zeb2 expression in pulmonary-residing melanoma cells promoted the development of macroscopic lesions. In vivo fate mapping made clear that melanoma cells undergo a conversion in state where ZEB2 expression is replaced by ZEB1 expression associated with gain of an invasive phenotype. These findings suggest that reversible switching of the ZEB2/ZEB1 ratio enhances melanoma metastatic dissemination.Significance:ZEB2 function exerts opposing behaviors in melanoma by promoting proliferation and expansion and conversely inhibiting invasiveness, which could be of future clinical relevance.

Supplementary Figures. Supplementary Figure S1: Zeb2-wildtype cells outcompete Zeb2-negative cells in terms of expansion and differentiation. Supplementary Figure S2: Zeb2 does not accelerate melanoma development on a p53-wildtype background. Supplementary Figure S3: ZEB2 affects the phenotypical switch between proliferation and invasion in mouse and human melanoma cells. Supplementary Figure S4: ZEB2 affects the phenotypical switch between proliferation and invasion in human melanoma. Supplementary Figure S5: TGF-ß treatment mediates the switch from ZEB2 to ZEB1 and induces an invasive gene signature.

Supplementary materials and methods

Supplementary Figures 1-6. Suppl. Fig. 1. Mel-ILP induces release of certain cytokines, however does not affect infiltration of immune cells into tumor bed. Suppl. Fig. 2. Melphalan induces apoptosis of melanoma cells. Suppl. Fig. 3 Melphalan induces exposure of danger signals. Suppl. Fig. 4. Dying human melanoma cells induce danger signaling-independent in vitro stimulation of immune cells. Suppl. Fig. 5. In vitro treated melanoma cells do not strongly activate NK cells. Suppl. Fig. 6. (A) The phenotypic maturation of murine iDCs (B) Effect of antibodybased elimination of CD4+ and CD8+ cells in prophylactic mice vaccination experiment

Supplementary Tables 1-3. Supplementary Table 1. Meta-data analysis of clinical response to melphalan-based isolated limbtreatment procedures in melanoma patients. Supplementary Table 2. Meta-data analysis of clinical response to melphalan/TNF or Mel/TNF/IFNγ combination therapies for isolated limb-treatment procedures in melanoma patients. Supplementary Table 3. Follow up information about the patients whose tumour samples were used for analysis of infiltration of immune cells and expression levels of cytokines.

Systemic chemotherapy generally has been considered immunosuppressive, but it has become evident that certain chemotherapeutic drugs elicit immunogenic danger signals in dying cancer cells that can incite protective antitumor immunity. In this study, we investigated whether locoregionally applied therapies, such as melphalan, used in limb perfusion for melanoma (Mel-ILP) produce related immunogenic effects. In human melanoma biopsies, Mel-ILP treatment upregulated IL1B, IL8, and IL6 associated with their release in patients' locoregional sera. Although induction of apoptosis in melanoma cells by melphalan in vitro did not elicit threshold levels of endoplasmic reticulum and reactive oxygen species stress associated with danger signals, such as induction of cell-surface calreticulin, prophylactic immunization and T-cell depletion experiments showed that melphalan administration in vivo could stimulate a CD8+ T cell–dependent protective antitumor response. Interestingly, the vaccination effect was potentiated in combination with exogenous calreticulin, but not tumor necrosis factor, a cytokine often combined with Mel-ILP. Our results illustrate how melphalan triggers inflammatory cell death that can be leveraged by immunomodulators such as the danger signal calreticulin. Cancer Res; 75(8); 1603–14. ©2015 AACR.

Male gender is independently and significantly associated with poor prognosis in melanoma of all clinical stages. The biological underpinnings of this sex difference remain largely unknown, but we hypothesize that gene expression from gonosomes may play an important role. The current study demonstrates that loss of the inactivated X chromosome in melanomas arising in females is strongly associated with poor distant metastasis-free survival, suggesting a dosage benefit of two X-chromosomes. The gonosomal PPP2R3B gene is located on the pseudo-autosomal region (PAR) of the X-chromosome in females and on the Y-chromosome in males. We observed that despite its location on the PAR that predicts equal dosage across genders, PPP2R3B expression is lower in males than in females, and is independently correlated with poor clinical outcome. PPP2R3B codes for the PR70 protein, a regulatory substrate recognizing subunit of PP2A, that decreases melanoma growth by negatively interfering with DNA replication and cell cycle progression through its role in stabilizing CDC6/CDT1 interaction that delays the firing of origins of DNA replication. As such, PR70 behaves functionally as an X-linked tumor suppressor gene. Citation Format: Léon C.L. Van Kempen, Margaret Redpath, Mounib Elchebly, Kathleen Oros Klein, Andreas Papadakis, James Willmott, Richard Scolyer, Per-Henrik Edqvist, Fredrik Ponten, Dirk Schadendorf, Anke van Rjk, Stefan Michiels, Anne Dumay, Anne Helbling-Leclerc, Philippe Dessen, Jasper Wouters, Marguerite Stass, Celia Greenwood, G. Elias Ghanem, Joost van den Oord, Jean Feunteun, Alan Spatz. The protein phosphatase 2A regulatory subunit PR70 is a gonosomal melanoma tumor suppressor gene [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5528. doi:10.1158/1538-7445.AM2017-5528