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Tobacco and alcohol responsible for head and neck cancers among people from North East India, shows study

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8 Mar 2018

Cancer, the silent killer, comes in various types and forms. One of them is the head and neck cancer -- a group of cancers that start within the mouth, nose, throat, larynx, sinuses or salivary glands. It is the most commonly diagnosed cancer worldwide, and about 90% of all head and neck cancers are squamous cell carcinomas (HNSCC), says a report from the World Health Organization. Squamous cell carcinoma is an uncontrolled growth of abnormal cells arising in the squamous cells, which compose most of the skin’s upper layers.

Studies show that in India, people from the northeastern states--Assam, Manipur, Mizoram, Tripura and Nagaland -- have the highest incidence of head and neck cancers in the country. Now, a study by researchers from the Assam University, University of Science and Technology, Meghalaya; University of Kalyani, and the Institute of Advanced Study in Science and Technology, Guwahati, explores some of the reasons behind this observation. The study, published in Tumor Biology: Journal International Society for Oncology and Biomarkers, also suggest biomarkers for early, efficient and comprehensive diagnosis of HNSCC.

The researchers collected data from 50 healthy individuals and 50 individuals suffering from head and neck cancers about their age group, gender, lifestyle and tobacco-consumption habits. They then analysed this data and found that lifestyle and tobacco-consumption habits played a significant role in the incidence of cancer.

“The practice of betel quid chewing, primarily consumed with betel leaf and slaked lime, along with using smokeless tobacco products (khaini, zarda and gutkha) and cigarette smoking, contribute to the risk of HNSCC in these states. Also, using a kitchen with minimal ventilation and continuous exposure to household smoke from burning firewood plays a big role", says Dr. Rosy Mondal, a scientist at the Institute of Advanced Study in Science and Technology, Guwahati, and an author of the study.

For the study, the researchers also isolated ‘cell-free mitochondrial DNA’ from the blood plasma of the two study groups -- one that had healthy individuals, and the other with those who suffered from HNSCC. “Cell-free mitochondrial DNA is the freely circulating mitochondrial DNA. They are also referred to as cell-free DNA because they are not present inside the cell, rather circulate freely in the bloodstream”, explains Dr. Mondal.

The researchers then studied the relationship between the content of mitochondrial cell-free DNA, the nuclear DNA present in the cells, with the habit of using quid chewing, smoke and smokeless tobacco. It was done to establish the potential use of these DNAs as an early diagnostic marker. The results showed that there was a significant difference in the level of the cell-free DNA between HNSCC cases and control.

So what are the benefits of using cell-free DNA as a biomarker for detecting cancer? “The presence of certain changes in a tissue obtained invasively, via biopsy, for example, are considered biomarkers in cancer. These biomarkers could show some abnormality, or it could show the presence or absence of a membrane receptor, which could indicate cancer. Cell-free DNA acts as a non-invasive analysis of tumour-derived genetic material”, explains Dr. Mondal. “A non-invasive biomarker is simply one that can be obtained easily and without ‘harming’ the patient. It could lead to efficient screening and comprehensive monitoring of HNSCC, which could be very beneficial for the management of the corresponding disease burden in the states of northeast India”, she adds.

This study is the first of its kind that relates the increased cell-free mitochondrial DNA content in patients with HNSCC, to the habits of betel quid chewing, using smoke and smokeless tobacco, and other lifestyle habits. The study also shows the likely use of cell-free DNA as a non-invasive biomarker in detecting cancer early on.