“Evaluation of The Effect of Cisplatin and Low-Level Laser Irradiation on Head and Neck Squamous Cell Carcinoma Cell Line” In Vitro Study

Abstract

Cisplatin is a potent and widely used first-line chemotherapeutic agent for HNC. Anticancer action of cisplatin is principally mediated through induction of mitochondrial (intrinsic) apoptosis. Cisplatin accumulates preferentially in the mitochondria and cross-links mitochondrial DNA to form nonfunctional adducts, causing transcription blockage and impaired synthesis of many ETC elements. Subsequently, ROS build up to incite a state of mitochondrial oxidative stress, leading to p53-dependent upregulation of proapoptotic Bax protein, which allows for the exodus of Cyt c to the cytosol in order to further activate the executioner caspases 3, 6 and 7. Despite its well-verified efficacy, cisplatin has catastrophically toxic side effects, such as nephrotoxicity, ototoxicity, hepatotoxicity and myelotoxicity, especially when administered at high doses. So, novel combination therapies have been continuously improvised to overcome the limitations of the high-dose chemotherapy by potentiating its effect, precluding the need for application of such large doses. One of the emerging treatment modalities for cancer is laser photochemotherapy, which combines LLLI with chemotherapy. The results of this approach proved fruitful in experimental studies. LLLI or PBM is a therapeutic procedure, in which laser light photons in the visible red or NIR spectrum is utilized to create biological alterations in the irradiated cells, through induction of a photochemical reaction, after being absorbed by the mitochondrial chromophore (Cox). Manipulating some LLL parameters, like fluence, in a way that inflicts phototoxic damage on irradiated cells (according to the biphasic dose-response law), made some researchers employ PBM as a potential anticancer modality, even when used solely. HF-LLLI-associated apoptosis has been found to be, like cisplatin, mitochondrially driven. PBM at high fluence causes overstimulation of Cox, to the extent that Cox may get inactivated, resulting in disturbed flow of electrons inside the mitochondria. The end result is accumulation of ROS, generating a mitochondrial oxidative stress, that signals in the same manner like that of cisplatin. Therefore, the mitochondrion serves as a common target for both cisplatin and LLLI, making them a perfect combination. The aim of the present study was to investigate the effect of cisplatin and LLLI (at a fluence of 190.91 J/cm2), individually and in combination with each other, on cultured HEp-2 cells. The primary aim was to explore if PBM can exert a joint effect on cisplatin apoptosis-inducibility in HEp-2 cells. The evaluation of their effects was at the molecular level by assessment of the levels of two surrogate markers for mitochondrial apoptosis, Bax gene expression (by qRT-PCR) and Cyt c release (by ELISA), in addition to the evaluation of apoptosis at the cytomorphologic