RH-18

Pannexin 1 Induces Rhabdomyosarcoma Cell Fusion by Downregulating APOBEC2

Rhabdomyosarcoma (RMS) is an aggressive cancer thought to arise from impaired myogenesis. This can be substantially overcome by increasing the levels of pannexin 1 (PANX1), a critical component of the myogenic program, but the mechanism involved is unknown.

Using RNA-seq, we have previously found that overexpression of PANX1 dramatically reshapes the transcriptomic landscape of RMS including downregulation of a myogenic modulator, APOBEC2 (apolipoprotein B mRNA editing enzyme catalytic subunit 2). Following this clue, we investigated the regulation of APOBEC2 expression by PANX1 in RMS.

APOBEC2 levels were analyzed over eight days in our stable RMS cell lines in which PANX1 was overexpressed under the control of a cumate switch system. APOBEC2 levels increased in most control cells as they proliferate, which was significant after eight days in Rh28, Rh30, Rh41, and RD cells (Fig. 1A-L). Notably, PANX1 overexpression significantly decreased the expression of APOBEC2 in Rh28, Rh30, and RD cells compared to their respective controls but not in Rh36, Rh41 and Rh18 (Fig. 1A-L). The decrease in APOBEC2 protein levels in Rh28, Rh30 and RD cells was similarly associated with a significant decrease in its mRNA expression (Fig. 1M, N, R). Accordingly, APOBEC2 transcript expression was not affected by the upregulation of PANX1 expression in Rh41, Rh18, and Rh36 cells (Fig. 1O, P, Q). Western blot analysis showed a downregulation of APOBEC2 levels when PANX1 expression was increased in Rh30 xenografts (Fig. 1S, T), suggesting that this regulation also occurs in vivo. These results indicate that, in some RMS cell lines, increasing PANX1 levels leads to a downregulation of APOBEC2 expression at both the transcript and protein level.