Activation of RhoA/ROCK2 signaling by hypoxia-inducible factor 1α in promoting tumor growth and metastasis in human colon cancer

Background: Recent evidence strongly suggests the profound role of the tumor microenvironment in cancer development and progression. A hypoxic microenvironment is widely acknowledged to be a typical feature of solid tumors, and altered hypoxia-inducible factor 1 alpha (HIF-1 alpha) expression has been associated with the formation and the progression of many solid tumors; however, the underlying mechanism of this relationship remains obscure. Methods: Clinical colorectal cancer tissue samples were collected to detect the differential expression of HIF-1 alpha, Ras homolog family member A (RhoA), and Rho-associated, coiled-coil containing protein kinase 2 (ROCK2). With hypoxic stress, small interfering RNA (siRNA) targeting HIF-1 alpha, lentivirus transfection of RhoA was used to study the mechanism of HIF-1 alpha and RhoA/ROCK2 signaling pathways in the growth and metastasis of colon cancer. Results: According to Cell Counting Kit 8, wound-healing, and Transwell assays, HIF-1 alpha expression activated the RhoA/ROCK2 pathway within colon cancer cell lines, accelerating their growth and expansion. In cells transfected with LV-RhoA, inactivating the RhoA/ROCK2 pathway with the specific inhibitor Y-27632 decreased tumor growth and metastasis under hypoxic conditions, while activating the RhoA/ ROCK2 pathway restored these biological properties. The Western blot results showed that the expression levels of pMYPT1, cyclin D1, and MMP2 in the siRNA + LV-RhoA group were also significantly increased compared with those in the siRNA group. Conclusions: For the first time, this study demonstrated that HIF-1 alpha can promote the growth and metastasis of colon cancer via directly affecting RhoA/ROCK2 signaling and thus represents a novel therapeutic target for colon cancer.