TOKYO -- Researchers have identified through genetic testing six categories of liver cancer occurring among Japanese, a discovery having broad implications toward developing diagnoses and treatments for the disease.
The findings have been published in the U.S. scientific journal Nature Genetics.
Liver cancer is caused in part by genetic mutations occurring during cell replication. Scientists from Japan's National Cancer Center, the Riken research institute, the University of Tokyo and elsewhere mapped out the genomes of liver cancer tissues surgically removed from 300 patients and compared them with genomes of healthy livers. Supercomputers pinned down six types of liver cancers based on where the mutations occur.
A five-year survival rate of 80% is possible depending on the type of liver cancer. But one type affecting the p53 gene, a tumor suppressor, has a mere 20% survival rate. That category appears in one-fifth of the patients. Another cancer arising from mutated ARID2 suppressor genes has a 0% survival rate.
The researchers also discovered that a liver cancer cell contains 10,000 mutations on average. In addition, the scientists unearthed more than 10 new genes thought to be connected to the outbreak and advancement of cancer.
Normally, one group of anticancer drugs is used universally to treat the same cancer. But targeted therapies, which interfere with cancer-causing proteins generated by mutated genes, have emerged in recent years. Those types of treatments have been effective against chronic myeloid leukemia and cancers affecting the lungs, breasts and other parts of the body. The therapies also come with fewer side effects.
However, no targeted therapy exists for liver cancer. The identification of six types of mutations common among Japanese for that cancer has spurred hope for the development of such treatments.
About 40,000 people are diagnosed with liver cancer in Japan yearly, with over 30,000 dying from the disease. The Japanese Association of Clinical Cancer Centers reports an overall five-year survival rate of roughly 35% and a 10-year survival rate of about 15%.