MACC1, Metastasis associated in colon cancer 1, is a newly identified prognostic biomarker for colorectal cancer metastasis and patient survival, when determined in the primary tumor or patient blood. MACC1 induces cell motility and proliferation in cell culture and metastasis in mouse models. MACC1 acts as a transcriptional regulator of the receptor tyrosine kinase gene Met via binding to its promoter. However, no information about the promoter of the MACC1 gene and its transcriptional regulation has been reported so far. Here we report the identification of the MACC1 promoter using a promoter luciferase construct that directs transcription of MACC1. To gain insights into the essential domains within this promoter region, we constructed 5' truncated deletion constructs. Our results show that the region from -426 to -18 constitutes the core promoter and harbors functional motifs for the binding of AP-1, Sp1, and C/EBP transcription factors as validated by site directed mutagenesis study. Using electrophoretic mobility shift assay and chromatin immunoprecipitation assay, we demonstrated the physical interaction of these transcription factors to a minimal essential MACC1 core promoter sequence. Knock down of these transcription factors using RNAi strategy reduced MACC1 expression (P < 0.001), and resulted in decrease of cell migration (P < 0.01) which could be specifically rescued by ectopic overexpression of MACC1. In human colorectal tumors, expression levels of c-Jun and Sp1 correlated significantly to MACC1 (P = 0.0007 and P = 0.02, respectively). Importantly, levels of c-Jun and Sp1 also showed significant correlation to development of metachronous metastases (P = 0.01 and P = 0.001, respectively). This is the first study identifying the MACC1 promoter and its transcriptional regulation by AP-1 and Sp1. Knowledge of the transcriptional regulation of the MACC1 gene will implicate in enhanced understanding of its role in cancer progression and metastasis.

Metastasis is a multistep molecular network process, which is lethal for more than 90% of the cancer patients. Understanding the regulatory functions of metastasis-inducing molecules is in high demand for improved therapeutic cancer approaches. Thus, we studied the post-transcriptional regulation of the crucial carcinogenic and metastasis-mediating molecule metastasis associated in colon cancer 1 (MACC1). In silico analysis revealed MACC1 as a potential target of miR-218, a tumor suppressor miRNA. Expression of these two molecules inversely correlated in colorectal cancer (CRC) cell lines. In a cohort of CRC patient tissues (n = 59), miR-218 is significantly downregulated and MACC1 is upregulated compared with normal mucosa. Luciferase reporter assays with a construct of the MACC1-3′-UTR harboring either the wild type or the mutated miR-218 seed sequence confirmed the specificity of the targeting. miR-218 inhibited significantly MACC1 protein expression, and consistently, MACC1-mediated migration, invasion and colony formation in CRC cells. Anti-miR-218 enhanced the MACC1-mediated migration, invasion and colony formation. Similar findings were observed in the gastric cancer cell line MKN-45. Further, we performed methylation-specific PCR of the SLIT2 and SLIT3 promoter, where miR-218 is encoded in intronic regions. The SLIT2 and SLIT3 promoters are hypermethylated in CRC cell lines. miR-218 and SLIT2 expressions correlated positively. Methyltransferase inhibitor 5-Azacytidine induced miR-218 expression and inhibited the expression of its target MACC1. We also determined that MACC1 has alternative polyadenylation (APA) sites, which results in different lengths of 3′-UTR variants in a CRC cell line. Taken together, miR-218 is post-transcriptionally inhibiting the MACC1 expression and its metastasis-inducing abilities.

The S100 calcium-binding protein A4 (S100A4) induces epithelial mesenchymal transition, migration, invasion, angiogenesis and metastasis. Its induced expression in several cancer types correlates with poor prognosis. Apart from the functional and transcriptional regulatory aspects of S100A4, its post-transcriptional regulation is not yet clearly elucidated. In this study, we show that microRNAs (miR) miR-505-5p and miR-520c-3p target the 3′-UTR of S100A4 and inhibits its expression and its mediated migration and invasion. 5-Aza treatment significantly increased miR-520c-3p expression and reduced the S100A4 protein amounts. The upstream promoter region of miR-520c is hypermethylated irrespective of the metastasis status of colorectal cancer (CRC) patient tissues and in all analyzed CRC cell lines. Moreover, in a cohort of CRC patient specimen (n = 59), miR-520c-3p was significantly downregulated. miR-520c-3p stably expressing HCT116 cells showed a reduced metastasis formation in livers after implanting in mice spleen. Taken together, our findings demonstrate that S100A4 is post-transcriptionally regulated by tumor suppressor miRs, miR-505c-5p and miR-520c-3p, and particularly miR-520c-3p expression is epigenetically silenced in CRC.