Genetic variant in SPDL1 reveals novel mechanism linking pulmonary fibrosis risk and cancer protection

Idiopathic Pulmonary Fibrosis (IPF) is a rare disease with poor prognosis. By contrast, cancer is common in any elderly population and a leading killer, but is now often curable. Of note, whereas IPF is driven by cellular senescence, cancer is characterized by uncontrolled cell division. Using data available from two large biobank-based studies (Finnish FinnGen study and UK biobank), we conducted a comprehensive analysis of the shared genetic background of IPF and cancer. In a population sample of 218,792 Finns with complete longitudinal health histories, we estimated the effect of individual genetic variants to the lifetime risk of IPF and cancer. We extend the analysis from IPF-GWAS to pan-cancer meta-analysis over FinnGen and UK Biobank and finally to the identification of genetic drivers of somatic chromosomal alterations. We detected six loci (SPDL1, MAD1L1, MAP2K1, RTEL1-STMN3, TERC-ACTRT3, OBFC1) associated with both IPF and cancer, all closely related to cellular division. However, each individual signal is found with opposite effects over the two diseases, termed as antagonistic pleiotropy. Several of these loci (TERC-ACTRT3, RTEL1-STMN3, OBFC1) are among the strongest inherited factors for constitutive telomere length variation and consistently indicate that shorter telomere length would increase the risk for IPF but protect from malignancy. However, a Finnish enriched SPDL1 missense variant and a common MAD1L1 intronic variant had no effect on telomere length but were shown to protect individuals from accumulation of somatic mutations. The decreased risk of cancer in SPDL1 and MAD1L1 variant carriers might result from a lower number of chromosomal alterations accumulated over time, conversely leading to fibrosis in the lung due to cellular senescence-induced inflammation. We hypothesize that the SPDL1 missense variant functions as gain-of-function mutation, leading to cellular senescence, a barrier to cancer and a driver of fibrosis in IPF. If translated to therapy, these findings might not only be able to offer relief to individuals with IPF, but also to protect from onset of cancer.