Abstract 3881: HOXA1 drives melanoma tumor growth and metastasis and elicits an invasion gene expression signature that prognosticates clinical outcome.
Authors: Wardwell-Ozgo Joanna , Dogruluk Turgut , Gifford Armel , zhang Yiqun , van Doorn Remco , Creighton Chad , Scott Kenneth 
Published: August 2014

The majority of cutaneous melanoma patients present with no evidence of metastasis at diagnosis. For those patients, primary tumor excision generally confers a favorable prognosis. However, approximately 15% of these patients will eventually succumb to the aggressive, lethal metastatic disease. Currently we possess a limited understanding of the genetic events driving progression of melanoma, particularly those responsible for its metastatic propensity and much effort is focused on identifying pro-metastatic genetics aberrations or perturbed signaling networks that constitute potential new therapeutic targets. To address this question we recently reported an oncogenomics-guided screening approach designed to identify genetic drivers of early-stage melanoma metastasis.

We functionally validated and assessed the mechanism-of-action by which homeobox transcription factor A1 (HOXA1), the top-scoring enhancer of cell invasion identified by our screen, contributed to melanoma progression by in vivo and in vitro biochemical and genetic assays. Transcriptome and pathway profiling analyses of cells expressing HOXA1 revealed up-regulation of factors involved in diverse cytokine pathways that include the TGFβ signaling axis, which we further demonstrated to be required for HOXA1-mediated cell invasion. Transcriptome profiling also showed HOXA1’s ability to potently down-regulate expression of microphthalmia-associated transcription factor (MITF) and other genes required for melanocyte differentiation, suggesting a mechanism by which HOXA1 expression de-differentiates cells into a pro-invasive cell state concomitant with TGFβ activation. Our analysis of publicly available datasets indicated the HOXA1-induced gene signature successfully categorizes melanoma specimens based on metastatic potential and, importantly, is capable of stratifying melanoma patient risk for metastasis based on expression in primary tumors independent of current pathological staging characteristics.

We identified putative HOXA1 effector genes by defining the HOXA1 “targetome” via an integrated analysis of HOXA1 transcriptome and ChIP-SEQ data. We will leverage our collection of ∼32,000 sequence-verified cDNA clones and molecular barcoding technology to perform pooled genetic screens for enhancers of in vitro cell invasion and in vivo tumorigenesis. We will then validate top scoring HOXA1 effector candidates and investigate their mechanisms-of-action in the context of metastatic melanoma.

Together, these validation data and mechanistic insights suggest that patients whose primary tumors express HOXA1 are among a high-risk metastasis subgroup that should be considered for anti-TGFβ therapy in adjuvant settings. Moreover, further analysis of HOXA1 target genes in melanoma may reveal new pathways or targets amenable to therapeutic intervention.

Citation Format: Joanna Wardwell-Ozgo, Turgut Dogruluk, Armel Gifford, Yiqun zhang, Remco van Doorn, Chad Creighton, Kenneth Scott. HOXA1 drives melanoma tumor growth and metastasis and elicits an invasion gene expression signature that prognosticates clinical outcome. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3881. doi:10.1158/1538-7445.AM2013-3881