RGS5, a protein that promotes apoptosis and resists tumour cell proliferation, is also a member of the RGS R4 family, is involved in the negative regulation of the GPCR cycle and is a hallmark molecule of tumour-associated pericytes; however, in the tumour microenvironment, proapoptotic RGS5 can be restricted by other regulatory signals or can even be converted to antiapoptotic RGS5 to enhance pericyte survival, and high expression in several cancers is associated with poor tumour growth and prognosis [125, 126]. Here, RGS5 is linked to cancer.