Clinical and therapeutic significance of sirtuin-4 expression in colorectal cancer

Several members of the sirtuin family (SIRT1-7), which are a highly conserved family of NAD+-dependent enzymes, play an important role in tumor formation. Recent studies indicate that SIRT4 acts as a tumor suppressor by regulating glutamine metabolism. In the present study, we investigated the expression and activity of SIRT4 in colorectal cancer. Using a tissue microarray of 89 colorectal cancer cases, we found that SIRT4 was significantly downregulated in colorectal cancer tissues compared with that noted in the corresponding normal tissue (P<0.001). Lower SIRT4 levels were associated with worse pathological differentiation (P=0.031) and poorer post-operative overall survival rate (P=0.041). We found that SIRT4 overexpression inhibited the proliferation of colorectal cancer cells in vitro and in vivo. SIRT4 inhibited the glutamine metabolism of colorectal cancer cells and synergistically with glycolysis inhibitors induced cell death. SIRT4 also increased the sensitivity of colorectal cancer cells to chemotherapeutic drug 5-fluorouracil by inhibiting the cell cycle. Together, these results highlight the prognostic value of SIRT4 in colorectal cancer and the potential application of SIRT4 in colorectal cancer treatment.