There is no evidence that multiple sclerosis (MS) directly causes most cancers, but according to a new study in China, having the condition may slightly increase the risk of cervical cancer.
The study found no causal relationship between MS and 15 types of cancer except cervical cancer, the researchers wrote.
However, the team emphasized that their “robust” analysis “showed that MS was associated with only a marginally increased risk of cervical cancer.”
Study, “Association between multiple sclerosis and cancer risk: a two-sample Mendelian randomization studypublished in PLoS One.
Using Mendelian analysis to investigate the relationship between MS and cancer
MS occurs when the body’s immune system mistakenly attacks the protective covering of nerve fibers in the brain and spinal cord, leading to a wide range of symptoms. It is not yet clear why this happens, but it may be caused by a combination of environmental and genetic factors.
Research on MS and cancer has shown mixed results. While some studies suggest that MS may protect against cancer, others suggest that it may increase the risk of such diseases.
Now, a team from the Sun Yat-sen University Cancer Center in Guangzhou turned to Mendelian randomization to better assess the causal effect of MS on cancer—without potential confounders that could affect the results. A confounder is an unmeasured variable that affects both the hypothesized cause and effect of a study.
Mendelian randomization is a type of analysis that uses genetic variation as a proxy for the exposure of interest—in this case, genetic variation associated with increased susceptibility to multiple sclerosis as a proxy for MS—to examine the association between exposure and outcome.
If there is a causal relationship between the two, this relationship should also be seen between genetic variants associated with greater susceptibility to MS and cancer.
MS genetic data from more than 115,000 samples were obtained from the International Multiple Sclerosis Genetics Consortium, while cancer data from UK Biobank, a database of genetic and health information from more than 500,000 volunteers. has been achieved
Overall, the researchers identified 107 single nucleotide polymorphisms (SNPs), or changes at a single position in DNA, that were strongly associated with MS. However, five cases were associated with smoking and Epstein-Barr virus, which are risk factors for MS and cancer, and were therefore excluded from the analysis.
More research is needed on the biological mechanisms underlying this link
The researchers then sought to determine whether the remaining 102 SNPs were associated with any of the 15 cancers recorded in the UK Biobank. These included prostate, breast, bladder, brain, cervix, throat, liver and lung cancers. Other types such as ovarian, colorectal and melanoma (a skin cancer) were also included.
The results showed no causal link between MS and most cancers – specifically 14.
However, the researchers found that people with MS variants were 0.04 percent more likely to develop cervical cancer than those without these genetic changes.
The complex biological mechanisms underlying this relationship remain elusive and warrant further exploration.
The scientists wrote that “it is suspected that the incidence of premalignant conditions and cervical cancer may be related to drugs used in the treatment of MS.” But, the team noted, more research is needed to better understand this link.
“The complex biological mechanisms underlying this relationship remain elusive and warrant further exploration,” they wrote.
Overall, the team concluded, “This study suggests that MS is only causally associated with a marginally increased risk of cervical cancer and no association with other types of cancer.”
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