[5][6] STARD13 serves as a Rho GTPase-activating protein (GAP), a type of protein that regulates members of the Rho family of GTPases.

[7] It selectively activates RhoA and CDC42 and suppresses cell growth by inhibiting actin stress fiber assembly.

The protein was identified in part through its differential expression in cancers.

A low level of STARD13 was observed in less differentiated hepatocellular carcinoma tissue with higher RhoA expression.

A small patient study finds that the absence of STARD13 in hepatocellular carcinomas correlates with higher levels of RhoA and a poorer prognosis than patients with carcinomas that were STARD13-positive.