A series of new papers in the journal Nature has revealed the most comprehensive gene map ever of the genes causing cancer. It shows departures from normal behaviour i.e. mutations trigger a cascade of genetic misbehaviours that eventually lead to cancer.

What is Mutation?

• A mutation is a change that occurs in our DNA sequence, either due to mistakes when the DNA is copied or as the result of environmental factors such as UV light and pollution etc.
• Structural variations mean deletion, amplification or reorganization of genomic segments that range in size from just a few bases to whole chromosomes.
• Bases are the structural units of genes.
• Over a lifetime our DNA can undergo changes or ‘mutations’ in the sequence of bases A, C, G and T.

Why study cancer?

• Cancer is known to be a disease of uncontrolled growth.
• The growth process, like all other physiological processes, has genetic controls so that the growth is self-limiting. When one or more genes malfunction, the growth process can go out of hand.
• Not just cancer, there are many other diseases with a genetic link in varying degrees.
• Just a handful of “driver” mutations could explain the occurrence of a large number of cancers, the researchers said, raising hopes of a cancer cure being nearer than ever.

How big is the cancer burden?

• Cancer is the second most-frequent cause of death worldwide, killing more than 8 million people every year; incidence of cancer is expected to increase by more than 50% over the coming decades.
• 1 in 10 Indians will develop cancer during their lifetime, and one in 15 Indians will die of cancer, according to the World Cancer Report by WHO.
• The Northeastern states, UP, Rajasthan, West Bengal, Haryana, Gujarat, Kerala, Karnataka and Madhya Pradesh account for 44% of the cancer burden in India, says a recent analysis, published in The Lancet.

Is the genetic link to cancer well established?

• Yes, it is. One such association, for example, is of breast cancer with the BRCA 1 and BRCA 2 genes; the actress Angelina Jolie, who discovered that she carried the former gene, chose to undergo a preventive double mastectomy.
• This is personalised therapeutics where, instead of traditional toxic medications like chemotherapy, drugs that specifically target the delinquent genetic mutation are already being used.
• Such therapy, however, remains very expensive.

What is the new study that has oncologists around the world excited?

• It is a major international collaboration called the Pan-Cancer Analysis of Whole Genomes (PCAWG), in which researchers has published a series of papers after analysing some whole-cancer genomes and their matching normal tissues across 38 tumor types.
• They concluded that on average, cancer genomes contained 4-5 driver mutations when combining coding and non-coding genomic elements.
• This is the largest genome study ever of primary cancer.
• Various kinds of cancers required to be studied separately because cancers of different parts of the body often behave very differently from one another; so much so that it is often said that cancer is not one disease but many.

Breakthrough achievement of the study

• The mutations identified by the team have been catalogued. Identification and cataloguing of the genes is a very crucial step and has taken science’s understanding of cancer and its genesis ahead by several leaps.
• The catalogue, which is already available online, allows doctors and researchers from all over the world to look things up, consult and find information about the cancer of a given patient.
• The study has discovered causes of previously unexplained cancers, pinpointed cancer-causing events and zeroed in on mechanisms of development, opening new vistas of personalized cancer treatment to strike at the root of the problem.
• When it comes to drug development, however, the gene mapping is but a first step.

The next step

• The process of drug development will have to now kick in with pharmaceutical companies first identifying the compound(s) that target these gene mutations and then it being subjected to the rigours of clinical trials to prove its safety and efficacy.
• That could take anything from a few decades to a few years to cover all the mutations identified.

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