Mutational Signature Linked to Smoking Identified

New research has uncovered increased variation in the number and types of changes between individuals, indicating that a wide range of factors influence how bladder cancer develops.

New research has uncovered increased variation in the number and types of changes between people, indicating that a wide range of factors influence how bladder cancer develops. The findings of the study are published in Science. //

The study, conducted by scientists at the Wellcome Sanger Institute, the University of Cambridge, and their collaborators, provides an unprecedented view of bladder cancer's first steps.

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Bladder cancer occurs due to abnormal cell growth in the urinary bladder. The most common kind usually is urothelial cancer or transitional cell carcinoma.

The research provided fresh insights into the association between smoking and bladder cancer.

The study used DNA sequencing to better understand the genetic changes in healthy and diseased bladder tissue. University of Cambridge clinicians provided donated bladder tissue from five people with bladder cancer and 15 people with no cancer history.

DNA from 2,097 biopsies from the tissue samples was genome sequenced, and the sequences were analyzed to characterize the landscape of somatic mutations.

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High variability in the number and types of mutations and the frequency of 'cancer-driving' mutations between individuals suggested that a wide range of factors affect the accumulation of mutations in the bladder.

A new mutational signature is linked to smoking, shedding light on why tobacco is the single most significant risk associated with bladder cancer.

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Andrew Lawson, first author of the study from the Wellcome Sanger Institute, said: "One of the questions we sought to answer with this study was why bladder cancers have some of the highest mutation rates and cancer-driving mutations of any cancer type, even though the cells in the bladder divide slowly, reducing the chance of a genetic error. The high patient-to-patient variation in which genes were mutated and in the types of mutations may be consistent with the wide variety of factors that can contribute to bladder cancer. Further studies on the causes behind this variation could help uncover hidden causes of bladder cancer."

Mutations in essential cancer genes such as TP53, FGFR3, and TERT were mostly absent from healthy bladder tissue.

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Thomas Mitchell, a senior author of the study from Cambridge University Hospitals and the Wellcome Sanger Institute, said: "Like many cancers, early diagnosis of bladder cancer gives the patient a much greater chance of survival. The presence of mutations in key cancer genes in bladder tumours that are usually absent in normal tissue opens up the possibility of looking for these changes in fragments of DNA that are present in urine. These 'liquid biopsies' could be a non-invasive way to screen for bladder cancer earlier, which could help reduce the number of people who die from this disease."

Bladder Cancer Facts & Figures

By the end of 2020, an estimated 81,400 adults in the United States will be diagnosed with bladder cancer.
Smoking accounts for 47% of bladder cancer cases.
Ninety percent (90%) of people with bladder cancer are older than 55.

Source-Medindia