Investigation on mechanism of wavelength-dependent laser on stimulative effects of prostate cancer

The use of laser therapy in urology against cancer has been increasing because of its advantages of minimal invasiveness and high accuracy. However, delivery of maldistribution of optical energy can lead to undesired stimulation of cancer cells, resulting in tumor recurrence and secondary tumor development. Therefore, this study aims to investigate the mechanism of the stimulative effects of wavelength-dependent laser exposure on prostate cancer. The human-derived prostate cancer cell line DU145 was injected on the back of a mouse and exposed to four different laser wavelengths (405, 532, 635, and 808nm) at a dose of 10J/cm². After the laser irradiation, histological analysis was performed to verify the angiogenic effects of the laser irradiation. In addition, molecular analysis using western blot and qPCR was conducted to confirm the mechanism of modulation effects on tumors after laser exposure. Among the wavelengths, the 808nm laser significantly increased relative tumor volume (V/V₀) up to 150% while the control group increased V/V₀ up to 45%. The results of histological analysis using HE and immunohistochemistry (IHC) staining showed that 808 nm laser increased the expression of angiogenesis-related factors and blood vessel formation in the tumor section. Furthermore, ERK signaling pathway and gene expressions were activated by 808nm laser. The current findings showed that, depending on the wavelength, photo-modulation effects may stimulate tumor growth in the tumor microenvironment. In addition, the molecular mechanism of modulatory effects was examined through the signaling pathway and genetic factors. Further studies will establish laser irradiation methods to minimize tumor stimulation and confirm the tumor-stimulating effect of the laser irradiation under various parameters against urological cancer.