Identification of SOX4 novel transcriptional targets

The SOX4 gene belongs to a family of transcription factors and we previously unveiled SOX4 gene amplification and over-expression in a subset of lung cancers, indicating it may constitute a driver oncogene. Here, we searched for SOX4 transcriptional targets and investigate their involvement in lung development and carcinogenesis. We abrogated SOX4 expression in the NIH-H522 lung cancer cell line, carrying SOX4 amplification and over-expression, using an inducible short-hairpin system. Global analysis of gene expression identified about 90 genes down-regulated after SOX4 abrogation many of them related to neural development. We also demonstrated recruitment of SOX4 to many of these promoters, evidencing their nature as direct transcriptional targets of SOX4. Most of these transcripts were significantly increased in lung cancer cells with ectopic SOX4 over-expression and in lung tumors with high levels of SOX4. Conversely, many of them exhibited significant low expression levels in embryonic fibroblasts from Sox4-/- mice. We generated H522-derived cells that down-regulate SOX4 in an inducible manner. The H522 cells were transfected with a tetracycline (tet) repressor expression construct and a tet-repressor-controlled expression vector (tet-on) containing a shSOX4. An stable clone, H522Tr-shSOX4-1, which down-regulate SOX4 expression by 90%, 48 hours after adding doxycycline, was chosen for further analysis. To determine the gene expression profile characteristic of SOX4 depleted expression we compared the global gene expression of the parental H522 cells to the H522Tr-shSOX4-1 cells at 0, 24 and 96 hrs after inducing the shSOX4 with doxycycline using the Whole Human Genome Microarray from Agilent.