New York, Sep 25 : Scientists have identified a single, small strand of microRNA, or miRNA, that plays a critical role in fighting cancer. The team at the University of Massachusetts-Amherst in the US found that the microRNA, called let-7, also has the ability to recognise and remember tumour cells like T-cells. This cellular memory is the basis for how vaccines work. The study, published in the journal Nature Communications, can help build new strategies for the next generation of cancer-fighting immunotherapies, the team said. 'Our bodies have T-cells, which are white blood cells that specialise in fighting both pathogens, think of the common cold, and altered cells of the organism itself, like tumour cells,' said Leonid Pobezinsky, associate professor of veterinary and animal sciences at UMass Amherst and the paper's senior author. When the T-cells recognise foreign antigens in our bodies, they turn into killer T-cells and attack whatever the pathogen may be, from the sniffles to Covid, or even cancer. After the killer T-cells have won their battle, most of them die. "Somehow a few survive, transform into memory cells and form an elite task force called the 'memory pool' -- they remember what that particular antigen looked like, so that they can be on the lookout for the next time it invades the body," said Pobezinsky. But, cancerous tumour cells work by tricking the killer T-cells, turning them off before they can attack and create a memory pool, leaving the cancer to metastasize unchecked. "What we've discovered is that a tiny piece of miRNA, let-7, which has been handed down the evolutionary tree since the dawn of animal life, is highly expressed in memory cells. The more let-7 a cell has, the less chance that it will be tricked by cancerous tumour cells, and the greater chance it has of turning into a memory cell," Pobezinsky said. If the memory cell isn't tricked by the cancer, then it can fight and, crucially, remember what that cancerous cell looks like. "Memory cells can live for a very long time," adds Pobezinskaya. "They possess stem-cell-like features and can live for 70 years," Pobezinsky said. Understanding how let-7 is regulated during treatment to enhance the memories and capabilities of our own immune systems is a promising avenue for further research, the scientists said. /IANS