CHEK2 and Cancer Risk: A Moderate-Penetrance Gene

CHEK2 in the DNA-Damage Response

The CHK2 kinase is activated by ATM after DNA double-strand breaks. It phosphorylates targets including CDC25 phosphatases, BRCA1 and p53, contributing to cell-cycle checkpoints, DNA repair and apoptosis.

Loss of CHK2 function modestly weakens the damage response rather than abolishing it, which fits with the moderate cancer risk that pathogenic variants confer.

Breast Cancer Risk

Pathogenic CHEK2 variants are associated with roughly a two- to threefold relative increase in breast cancer risk, giving an estimated lifetime risk in the region of 20 to 30 percent, modified substantially by family history.

Risk is higher for oestrogen-receptor-positive disease. Because the absolute risk is moderate, management typically emphasises enhanced screening rather than risk-reducing surgery.

The 1100delC Variant and Missense Variants

The CHEK2 c.1100delC truncating variant is a well-studied founder allele in European populations and much of the risk data comes from it. Some recurrent missense variants, such as I157T, appear to carry lower risk than truncating variants.

Treating all CHEK2 variants as equivalent overstates risk for the lower-impact alleles, so the specific variant should be identified.

Other Associations

Smaller increases in risk have been reported for colorectal, prostate, thyroid and kidney cancers, and for a second contralateral breast cancer. These associations are less firmly quantified than the breast cancer link.

CHEK2 is not associated with the high, syndromic risks seen in Li-Fraumeni syndrome despite CHK2 acting upstream of p53.

Interpretation Notes

A CHEK2 result should be managed through clinical genetics, using variant-specific and family-history-adjusted risk rather than a single population figure.

Monoallelic CHEK2 findings do not indicate a recessive syndrome, and a variant of uncertain significance is not actionable as a risk result.

Key Takeaways

• ·CHK2 is an ATM-activated checkpoint kinase; loss modestly weakens the damage response.
• ·Pathogenic variants give a moderate, family-history-modified breast cancer risk.
• ·Truncating variants (e.g. 1100delC) carry more risk than some missense variants (e.g. I157T).
• ·Management usually means enhanced screening, not risk-reducing surgery.