Polycomb protein family member CBX7 plays a critical role in cancer progression

Abstract

CBX7 is a polycomb protein that participates in the formation of polycomb repressive complex 1. Apart from few exceptions, CBX7 expression is lost in human malignant neoplasias and a clear correlation between its downregulated expression and a cancer aggressiveness and poor prognosis has been observed. These findings indicate a critical role of CBX7 in cancer progression. Consistently, CBX7 is able to differentially regulate crucial genes involved in cancer progression and in epithelial-mesenchymal transition, as osteopontin and E-cadherin. Recent evidences indicate a role of CBX7 also in the modulation of response to therapy. In conclusion, CBX7 represents an important prognostic factor, whose loss of expression in general indicates a bad prognosis and a progression towards a fully malignant phenotype.

Keywords: CBX7; cancer progression; polycomb group.

Figure 1

Mechanisms leading the loss of CBX7 expression in human cancers. Several miRNAs are involved in the repression of CBX7 expression. In particular, HMGA1 protein exerts a double negative control directly on CBX7 promoter and indirectly by inducing the expression of miR-181b.

Figure 2

Mechanisms of cell transformation involving CBX7. CBX7 prevents cell transformation by sustaining E-cadherin expression and repressing Cyclin E and Osteopontin expression, through a mechanism involving the interaction with HDAC2 and HMGA1, respectively. Dashed lines indicate loss of regulatory action.