Centromere protein A knockdown inhibits rectal cancer through O6-methylguanine DNA methyltransferase/protein tyrosine phosphatase nonreceptor type 4 axis

Abstract

BACKGROUND

Centromere protein A (CENPA) exhibits an increased expression level in primary human rectal cancer tissues, but its role has not been investigated.

AIM

To clarify the specific role and mechanism of CENPA in rectal cancer progression.

METHODS

CENPA protein expression in rectal cancer tissues and cell lines were detected. CENPA was overexpressed and knocked down in SW837 and SW480 cells, and proliferation, invasion, apoptosis and epithelial-mesenchymal transition (EMT) marker protein levels were examined. O6-methylguanine DNA methyltransferase (MGMT) promoter methylation was assessed with methylation-specific polymerase chain reaction. Co-immunoprecipitation assay verified the interaction between MGMT and protein tyrosine phosphatase nonreceptor type 4 (PTPN4). SW837 cells with CENPA knockdown were injected subcutaneously into mice, and tumor growth was examined.

RESULTS

CENPA was upregulated in rectal cancer tissues and cell lines. CENPA overexpression promoted proliferation, invasion and EMT, and inhibited apoptosis in rectal cancer cells. Whereas CENPA knockdown showed the opposite results. Moreover, CENPA inhibited MGMT expression by promoting DNA methyltransferase 1-mediated MGMT promoter methylation. MGMT knockdown abolished the CENPA knockdown-mediated inhibition of rectal cancer cell progression. MGMT increased PTPN4 protein stability by inhibiting PTPN4 ubiquitination degradation via competing with ubiquitin-conjugating enzyme E2O for interacting with PTPN4. PTPN4 knockdown abolished the inhibitory effects of MGMT overexpression on rectal cancer cell progression. Moreover, CENPA knockdown inhibited xenograft tumor growth in vivo.

CONCLUSION

CENPA knockdown inhibited rectal cancer cell growth and attenuated xenograft tumor growth through regulating the MGMT/PTPN4 axis.

Keywords: Rectal cancer; Centromere protein A; O6-methylguanine DNA methyltransferase; Protein tyrosine phosphatase nonreceptor type 4; Proliferation; Invasion

Core Tip: This study suggested that centromere protein A (CENPA) was upregulated in rectal cancer tissues and cell lines. CENPA overexpression promoted proliferation, invasion and epithelial-mesenchymal transition, and inhibited apoptosis in rectal cancer cells. Whereas CENPA knockdown showed the opposite results. Additionally, CENPA knockdown inhibited xenograft tumor growth in vivo. Mechanistically, CENPA inhibited O6-methylguanine DNA methyltransferase (MGMT) expression by promoting DNA methyltransferase 1-mediated MGMT promoter methylation. MGMT interacted with protein tyrosine phosphatase nonreceptor type 4 (PTPN4) and increased PTPN4 protein stability. CENPA knockdown inhibited rectal cancer progression through regulating the MGMT/PTPN4 axis.