Association of Salivary Amino Acid With Oral Squamous Cell Carcinoma Identified by Liquid Chromatography Mass Spectroscopy

1. Introduction:

Oral cancer is an abnormal growth of tissue, originates from the tissue in and around the mouth which is uncoordinated with that of the surrounding normal tissue. Among all oral cancers, oral squamous cell carcinoma (OSCC) is the most common (90%) malignant epithelial neoplasm of the oral cavity. It is an alarming public health problem in the world due to its prevalence, high incidence rate and mortality. According to the recent data of GLOBOCAN 2020, 377713 newly diagnosed lip and oral cavity squamous cell carcinoma patients diagnosed worldwide which is about 2% of all cancer reported. Oral squamous cell carcinoma (OSCC) is the 6th most common cancer worldwide. Recent global reports suggest that the largest portion of the reported cases are from Asia (65.8%), but in the South Asia region, oral cancer is the 3rd most common cancer. One of the critical factor of the high mortality rate of OSCC is that initially many of the lesion is asymptomatic. As a result, they come at the late stage of the disease to the physician and ultimately have a poor prognosis. Research showed that, when an OSCC is in stage I, the 5-year survival rate is 80% but it drops to 20-40% when the disease is in stage IV. For the diagnosis of OSCC, after the initial clinical examination, incisional biopsy followed by histopathological examination is still considered as a gold standard, but the method has many limitations. Invasive procedure needs special expertise for taking biopsy sample from the representative areas and need expert histopathologist for confirmation. Moreover, taking a tissue sample from behind the visible area such as the base of the tongue, posterior pillar and incase of restricted jaw opening is very difficult or sometimes impossible.

Human saliva is the secretion from three major salivary gland parotid, submandibular, sublingual and numerous minor glands lie just beneath the mucosa of the oral cavity. It consists of water (99.5%), inorganic salts and enzymes (0.2%) and proteins (0.3%). It is helpful for the diagnosis of periodontitis, diabetes mellitus, HIV, dengue, mumps even breast cancer, pancreatic cancer, gastric cancer, lung cancer and oral cancer. Additionally, taking saliva samples has many advantages. Taking saliva is easier, and needs no invasive procedure or expertise. Besides, it has a sufficient amount of production and can be taken by the patient himself making the sample taking procedure cheaper. Salivary amino acids are the important metabolites for the diagnosis of a cancer patient. Amino acid is the raw product of protein synthesis. For this, when a cancer patient passes through a hypermetabolic and hypercatabolic state, there is a chance of protein imbalance. As the investigators know that amino acids are the byproducts of protein, it can give us a hint for the state of imbalance due to any cancer including oral squamous cell carcinoma. In addition, changes in amino acid concentration in the body fluid of cancer patient is significant according to several studies Mass spectrometry is a currently used platform for proteomics or metabolomics in biomedical research. Like other spectrometry method such as gas chromatography-mass spectrometry (GC-MS), capillary electrophoresis-mass spectrometry(CE-MS), two-dimensional electrophoresis mass spectrometry (2DE-MS), matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) and surface enhanced laser desorption ionization time-of-flight mass spectrometry (SELDI-TOF), Liquid chromatography-mass spectrometry (LC-MS) is widely used nowadays. It allows a quick and efficient separation and characterization of analytes in a given sample. Thus, it can help in rapid diagnosis of any disease by automated analysis of amino acid profiles with minimum effort and expenses. Many studies were conducted using LC-MS machine for saliva analysis for the diagnosis of several diseases and found significant results. To the best of my knowledge, very few studies were done to find out the salivary amino acid level from the patient having suspected oral lesion by LC-MS. Moreover, no study was performed for oral lesion diagnosis by analysis of amino acid profile using LC-MS in Bangladesh. The aim of this study is to find out the association of specific salivary amino acid levels with the patient of OSCC by Liquid Chromatography-Mass Spectrometry (LC-MS). 2. Rationale:

OSCC is the 6th most common cancer worldwide, but in Asia the largest portion was reported recently and in South-east Asia, it is the 3rd most common cancer. Poor socio-economic condition, lack of consciousness and widely use of tobacco, betel quid chewing and alcohol intake are the main factors behind this. Research showed that early diagnosis of cancer reduces the mortality rate and hence can improve the treatment outcome. As a result, scientists are trying to find out an easy, quick and reliable method of diagnosis of OSCC.

Although scalpel (incisional) biopsy followed by histopathological examination is still the gold standard for the diagnosis of the oral lesion but in the case of behind the visible area and in restricted mouth opening it is very difficult to collect the representative specimen. Moreover, the procedure is invasive and needs special equipment and expertise. In this aspect, to avoid the risk of invasive procedures and pain, body fluid analysis is the area of interest of the researcher nowadays.