Indian scientists peep into individual oral cancer cells

Indian biologists on Thursday reported gaining a critical insight into the behaviour of individual oral cancer cells, paving the way for development of diagnostic tools in future to screen oral cancer patients requiring specific types of treatment and management strategies.

The breakthrough happened when the scientists teaming up with doctors could manage to look at individual cancer cells and studied the “gene expression” level in single cells collected from oral cancer tissues.

“In earlier studies on oral cancer, we always got an overall picture as we saw a large number of different types of cells. This is like listening to chorus music where you don’t get to know much about individual singers,” Arindam Maitra, a senior scientist at the National Institute of Biomedical Genomics, Kalyani and one of the corresponding authors of the study, told DH.

“But now we can figure out how individual cells behave. This is akin to knowing about the ability of individual singers from a chorus.”

Oral cancer is the most frequent cancer among men in India. Every year around 77,000 new cases and 52,000 deaths are reported annually, which is approximately one-fourth of global incidences. Most of the oral cancers are detected late and come with a high degree of recurrence and mortality.

In the sub-continent, the disease is mainly caused by tobacco-chewing. While many of them die, the facial features of those who survive are terribly distorted since the tumour has to be surgically removed. Also in many patients, cells from the oral tumour migrate to other organs, notably lymph nodes, such as tonsils, leading to lymph node cancer, which is also highly fatal.

Over the years, doctors have noticed that all oral cancer patients don’t respond to the treatment similarly. There is a lot of variability in clinical features and progression among oral cancer patients.

It has long been surmised that such a variability occurs mainly because cancer tissues across patients have significant differences in types and numbers of different cells that express different sets of genes.

The NIBMG team working together with doctors at Dr R Ahmed Dental College and Hospital, Kolkata now offers a scientific validation of such a surmise.

“For years, cancer clinicians have noted and lamented that they do not understand why different oral cancer patients show such highly variable paths of progression. Our work provides considerable insight on this aspect. This shows cellular diversity and ecology of gene expression are so very different from one oral cancer patient to another,” said co-author Partha Majumder, National Science Chair (Scientific Excellence), Science & Engineering Board and founder director of NIBMG.

“This is India’s first study on gene expression levels in single cells collected from an oral cancer tissue. Such single-cell molecular biology studies provide deep insights on cancers and will result in better management and even treatment,” he added.

The researchers who have been studying cancer genomics for more than a decade said that the technology to carry out sequencing in individual cells and look at how genes orchestrate different cellular functions would provide insights into varying responses to cancer treatments. This will help clinicians to manage the patients efficiently.

This study has shown that the cellular ecosystem in oral cancer is highly variable from one patient to another.

Different types of cells in the human body perform different functions. When normal cellular function in a group of cells in an individual gets disrupted because of exposure to substances such as tobacco, these cells start to behave abnormally and are called malignant cells or simply cancer cells. This study has shown that the types and numbers of cancer cells in oral cancer patients are highly variable.

“Cancer cells are very dynamic in nature. In many patients they even recapitulate the behaviour of cancer stem cells which may be a dangerous reality for these patients,” Majumder said.

The scientists said better understanding of individual cell behaviour can be used for developing diagnostic assays that doctors can use. “What we used to see earlier in cancer tissues is only the tip of an iceberg. Most of the iceberg remained hidden under the water,” said Maitra.

The study has been published in the journal Cancer Science.