CLPP and cancer: Furthermore, the reduction of cell growth by simultaneous silencing of LONP1 and ClpP was significantly more pronounced following SHIN1 treatment compared with that in separate silencing experiments, whereas control siRNA-transfected cells showed only a marginal effect following SHIN1 treatment (Fig. 6G) These results demonstrate that SHMT2 is a key substrate of LONP1 and ClpP in cancer growth and resistance to cellular stress.