Cancer of the oral cavity including cancer of tongue is highly prevalent in India, probably because of high prevalence of risk factors leading to oral cancer like tobacco chewing, alcohol consumption, etc. Cancer is curable if detected early and if appropriate treatment is taken at early stages.
For cancer of the tongue, appropriate treatment is surgical removal of cancer from mouth along with removal of structures in the neck like lymph channels and lymph nodes, muscles etc, if there is evidence of spread of cancer in the neck. Spread of tongue cancer to neck requires extensive surgery involving removal of neck structures, a process called neck dissection. This spread can be either visible to eyes or it is not visible to eyes and seen only under microscope by a pathologist. However at present time the surgeons don’t have a method to find out if cancer has spread in the neck unless they do a neck dissection. So every patient of tongue cancer, irrespective of the fact that he has spread of cancer to neck, at present has to undergo invasive neck dissection. If he had a spread it’s beneficial to him to undergo neck dissection but if he does not have a spread the process is not only futile for him but he also faces various risks of neck dissection.
A research finding from Integrated Genomics Laboratory, ACTREC, Tata Memorial Centre, Navi Mumbai has provided some insights to find a way out of this dilemma for surgeons. Their study on 57 patients who had tongue cancer in early stages have shown that expression of a gene producing a protein called MMP10 (Matrix Metallic Proteinase 10) can serve as proxy marker of spread of cancer of tongue to neck.
Same gene is found to have abnormal high expression in various other cancers like breast, lung and colorectal in various previous reaserch studies. Interestingly the same gene expression is known to promote invasion and spread of cancer from one site to other site in previous studies. So the authors of this study have hypothesised that this protein MMP10 is responsible for spread of tongue cancer to neck. The authors have used sophisticated techniques like high throughput screening of samples collected from the patients using methods of whole exome sequencing and transcriptions sequencing. They have also used gene expression meta-analysis and validated candidate genes using immunohistochemical analysis.
In simple terms, this study suggest that when surgeon is operating on tongue cancer patient, he may first remove the cancerous tissue from tongue and before heading to neck dissection he can look for amount of MMP10 protein in cancerous tissue. This amount is detected with technique of immunohistochemical analysis where one applies a dye to colour the protein and depending upon the amount of colour one decides the amount of protein MMP10.
Higher amounts of MMP10 will mean that cancer has spread to neck and doctors can perform neck dissection. However if low amounts of MMP10 are found in cancerous tissue from tongue, the doctor need not do unnecessary neck dissection as it will be highly likely that no spread to neck has occurred. It is to be mentioned that this fact still requires to be proved on much larger number of patients than included in this study.
The strengths of this study is that it is among the first studies in research archives to investigate early stage of tongue cancer. Earlier studies from various parts of the world have investigated only late stages of tongue cancer when already the cancer has spread to neck. The limitation of this study is lack of survival data of patients and also the association of MMP10 expression with poor survival in early stage of tongue cancer remains to be verified in a larger sample set.
Though the research finding seems more academic, studies like this enrich scientific literature and are grounds on which future knowledge, research works and treatment methods evolve. We need to fund our scientists enough so that their research findings get converted to products that impact our healthcare and economy as well.