Lichen planus is a common chronic inflammatory mucocutaneous disease and the involvement of oral mucosa is often seen in 50% of cases. So far, the etiopathogenesis of oral lichen planus (OLP) has still been poorly understood, but T cell-mediated immunity and inflammatory pathways play a role in its pathogenesis [1]. Many studies proposed autoimmune properties of OLP such as interaction with other autoimmune diseases, reduced immune-suppressing activity in patients with OLP, and the presence of auto-toxicity cells cause them to be selected for research about inflammation and autoimmunity [2] From the first reported squamous cell carcinomas (SCC) developed from LP so far, several studies have focused on malignant transformation of OLP lesions to oral SCC (OSCC), as it has become a concerning topic in the world’s health. Nowadays, the term “oral lichen planus” is known as a precancerous condition, using the World Health Organization (WHO) classification. The molecular mechanisms underlying the development of oral cancer are not clearly known in patients with OLP, but OLP lesions can evolve from normal epithelium or precancerous lesions and the basement membrane disruption may trigger the apoptotic keratinocytes [3].
OSCC is the most common neoplasia of the oral cavity and is a serious worldwide health problem; so, understanding the SCC biomarkers is essential for early diagnosis as well as better prognosis and prevention of disease recurrence and is a good way to decrease the mortality of patients. Malignant transformation of oral mucosa due to gene mutation in cell growth and its regulation causes increased proliferation of cells, abnormal keratinization, epithelial dysplasia, increased cell motility, and angiogenesis. Cancer occurs by genetic changes that cause deregulation of protein, poor cell division, and tissue differentiation, invasion, and metastasis [4].
Tumor indicators have been recently recognized for the early diagnosis of malignancy. In oral cavity carcinomas, different serum indicators including oncofetal proteins (alpha photoprotein CEA), B proteins and enzymes (LDH) have been studied. One of the most significant indicators is β2 microglobulin which is a protein with low molecular weight (11800 kDa). It is found on every cell’s surface except for erythrocytes which are considered as a light unchangeable chain of compatible histologic antigens [5]. It is abundant in monocytes and lymphocytes [6]. In the normal physiologic state, some amounts of β2microglobulin can be secreted to the cell or serum due to intracellular release and it is often extracted from the blood by kidneys [7–11]. Thus, β2net concentration of microglobulin (β2M) is measured by its production and secretion to serum and the amount of extraction by kidneys [12]. β2M concentration increases as the kidney's function reduce and cells' turnover increases [13]. Thus, in individuals with a healthy kidney, an increase in the β2M amount indicates the proliferation of the changed cells. Increasing β2M amount in serum was observed in some pathologic cases including kidney diseases, immunity deficiency, and autoimmune disease. Besides, there was a high level of β2M in some solid and hematologic cancers in the time of diagnosis [14, 15]. Saliva-based analysis has been proposed in recent years and the potentially abnormal markers of oral cavity appear in saliva directly or indirectly. Therefore, its application as a diagnostic fluid can be of special significance. Saliva is a diagnostic tool to assess markers due to its several advantages: a low-cost tool for monitoring, safe collection, non-invasive, convenient, simple and reproducible without causing discomfort for the patient [16–18].
Baliah et al., (2017) determined the β2M level in serum in patients with oral leukoplakia, oral submucous fibrosis and oral squamous cell carcinoma and compared to the control group. In total, 100 individuals were classified in four groups: the first group contained patients with oral leucoplakia based on the clinical and histopathological reports; the second group consists of patients with oral submucous fibrosis; the third group was diagnosed to have oral squamous cell carcinoma (OSCC) and the last one was the control group. Results have indicated that the mean level of β2M in the serum of the leukoplakia, oral submucous fibrosis, OSCC patients and in the control group was 2597 ± 148.6, 2187.68 ± 678.6, 3166.04 ± 357.7, and 1542.60 ± 377.70 ng/mL, respectively. There was a significant increase in the mean level of β2M concentration in the first and the third groups compared to the control group. However, an increase in β2M concentration in patients with oral submucous fibrosis was not statistically significant. The present study has supported the hypothesis of using β2M concentration as an indicator in patients with oral leukoplakia and oral squamous cell carcinoma [19].
Diwan et al., (2016) studied the role of β2M as a tumor indicator in OSCC and leucoplakia. For this purpose, 30 OSCC patients, 23 leukoplakia patients, and 20 normal individuals in the control group were analyzed. Using the logistic regression model, the effect of age and gender was removed from samples due to their influence on β2M concentration. Results showed that β2M concentration was higher in OSCC and leukoplakia patients compared to the control group. Thus, β2microglobulin in serum can be used as an indicator in the diagnosis of these diseases. Increasing the concentration of β2microglobulinwas positively correlated with grading the histology of OSCC [18].
Thus, considering the high prevalence of oral cancers and oral lichen planus in Zahedan, the lack of similar study, and proving that saliva is safe and useful as a diagnostic method of oral cancer and Lichen planus, we have analyzed the β2M concentration in these patients.