Melanoma metastasis suppression by chromosome 6: Evidence for a pathway regulated by CRSP3 and TXNIP

Loss of genetic material on chromosome 6 has been associated with progression of human melanomas. We showed previously that introducing chromosome 6 into metastatic human melanoma cell lines suppresses metastasis without affecting the ability of the hybrids to form progressively growing tumors. By subtractive hybridization comparing nonmetastatic chromosome 6-containing (neo6/C8161) versus parental (C8161) metastatic cells, the KISS1 metastasis suppressor gene was isolated. However, KISS1 mapped to chromosome 1q32. To identify upstream regulator(s) of (and downstream effectors of) KISS1, microarray hybridization comparing C8161 and neo6/C8161 variants was performed. TXNIP/VDUP1, a thioredoxin-binding protein, was expressed more highly in neo6/C8161 and in nonmetastatic melanomas. Increased TXNIP expression inhibited metastasis and up-regulated KISS1. Surprisingly, TXNIP also mapped to chromosome 1q. PCR karyotyping that refined the region on chromosome 6 identified CRSP3/DRIP130, a transcriptional coactivator, as a metastasis suppressor. CRSP3 transfectant cells had up-regulated KISS1 and TXNIP expression and were suppressed for metastasis. Quantitative real-time reverse-transcription PCR of clinical melanoma samples showed that loss of CRSP3 expression correlated with decreased KISS1 expression and increased metastasis. Thus, we implicated a specific gene on chromosome 6 in the etiology of melanoma metastasis and identified potential up-stream regulators of KISS1 and TXNIP.