The immunohistochemistry of invasive and proliferative phenotype switching in melanoma: a case report

Abstract

Purpose To date there remains no effective therapy for metastatic melanoma and at the molecular level disease progression remains poorly understood. Recent work by our group led to the development of a novel phenotype switching model for melanoma progression, wherein cells transition back-and-forth between states of proliferation and invasion to drive disease progression. To explore the model’s clinical relevance we interrogated phenotype-specific expression patterns in human melanoma patient material. Experimental Design A matched primary/metastasis pair from a human melanoma patient was obtained and immunohistochemically stained for proliferative and invasive phenotype markers. These were also stained for hypoxia and blood vessel markers. Results Proliferative phenotype markers Melan-A and Mitf showed consistent anti-correlation with invasive phenotype marker Wnt5A and hypoxia marker Glut-1. These also correlated with observed intra-tumoural vascularisation patterns. Similar pattern distributions were present in both primary and metastasis samples. Strikingly, we observed that late phase metastatic melanoma cells adopt morphologies and behaviours identical to very early phase cells. Conclusions The expression patterns observed closely matched expectations derived from previous in vitro and xenografting experiments. These results highlight the likelihood that disease progression involves melanoma cells retaining the capacity to regulate the expression of metastatic potential critical factors according to changing microenvironmental conditions.

Hypoxia and MITF control metastatic behaviour in mouse and human melanoma cells

“…However, further studies, with a larger number of samples, are needed to assess the extent to which this phenomenon exists. Note that in agreement with this result, it has been reported that MITF showed a consistent anti-correlation with Glut1, a hypoxia marker, and a HIF1a target gene (Eichhoff et al, 2010).…”

Phenotype Switching: Tumor Cell Plasticity as a Resistance Mechanism and Target for Therapy

“…This included Wnt5a, which had previously been implicated in melanoma metastasis (10,11). Other studies have confirmed that melanoma cell lines segregate into these distinct expression clusters (12,13).…”

The Role of Cellular Differentiation and Cell Fate in Malignant Melanoma

“…Specifically, whereas melanoma cells in the primary tumor as well as the secondary metastatic tumor were shown to have a phenotype defined by low levels of the transcription factor Brn-2 and a high level of pigmentation, highly motile, actively metastasizing melanoma cells were shown to express a predominantly Brn-2-high/pigment-low phenotype (Pinner et al, 2009). In a patient-matched analysis of both a primary metastatic lesion and distant metastases, Eichhoff et al demonstrated that, consistent with our description of proliferative and invasive melanoma phenotypes, cells in the primary and distant tumors expressed high levels of MITF and Melan-A, while cells in the "unstructured" regions of these tumors (areas from which metastatic cells are most likely to be derived) stained heavily for WNT5A and far less for Mitf and Melan-A (Eichhoff et al, 2010). Strikingly, this study also revealed latestage metastatic melanoma cells adopted phenotypes and morphologies nearly identical to early-phase cells, indicating that melanoma cells have significant plasticity with regards to their gene expression profile (Eichhoff et al, 2010).…”

“…In a patient-matched analysis of both a primary metastatic lesion and distant metastases, Eichhoff et al demonstrated that, consistent with our description of proliferative and invasive melanoma phenotypes, cells in the primary and distant tumors expressed high levels of MITF and Melan-A, while cells in the "unstructured" regions of these tumors (areas from which metastatic cells are most likely to be derived) stained heavily for WNT5A and far less for Mitf and Melan-A (Eichhoff et al, 2010). Strikingly, this study also revealed latestage metastatic melanoma cells adopted phenotypes and morphologies nearly identical to early-phase cells, indicating that melanoma cells have significant plasticity with regards to their gene expression profile (Eichhoff et al, 2010). Lending further support to the existence of phenotype switching are the findings of Hoek et al, in which seed melanoma cells of either an exclusively proliferative or exclusively invasive phenotype were injected subcutaneously into immunocompromised mice (Hoek et al, 2008).…”

“…In contrast to the unidirectional genetic theory of melanoma progression is the fact that the proliferative transcriptional grouping is comprised of cell lines originating from primary tumors as well as from distant secondary metastases, while the invasive grouping predominantly contains pre-metastatic cells taken from the outer margins of a melanoma lesion, or metastatic melanoma cells collected during the actual process of intravascular migration (Eichhoff et al, 2010;Hoek et al, 2008). A Clark-like model of melanoma progression would instead predict that the proliferative grouping would be made up entirely of pre-metastatic cells, while the invasive grouping would contain mainly metastatic and postmetastatic cells (Miller and Mihm, 2006).…”