Low-level laser selectively inhibiting colorectal cancer cell metabolic activity and inducing apoptosis for delaying the development of intestinal cancer

Low-level laser irradiation (LLLI) is a novel approach that shows promise for the treatment of colorectal cancer (CRC). However, the molecular mechanisms underlying its biochemical effects and gene expression remain unclear. Here, LLLI (632.8 nm) was used to treat CRC RKO cells and normal small intestinal NCM460 cells. LLLI showed a significant dose- and time-dependent effect on cell viability, in which a single dose of irradiation at 15 J/cm2 selectively inhibited the growth of RKO cells but largely unaffected the activity of NCM460 cells. And then, LLLI produced an internal response, effectively reducing the level of H2O2 in tumor cells, downregulating the mitochondrial membrane potential, and improving the efficiency of apoptosis in CRC, but no internal response was observed in NCM460 cells under the same conditions. Furthermore, the expression of several important genes in the classical WNT pathway was significantly downregulated, and the pathway was inactivated after LLLI intervention, thereby inhibiting tumor cell growth. Simultaneously, TNF-α was effectively activated to stimulate the caspase family members of the death effector to initiate apoptosis led by the extrinsic pathway. LLLI successfully achieves tumor cell normalization while delivering a potent anticancer effect, expected to be a novel therapeutic modality for CRC.