Causal Inference between Rheumatoid Arthritis and Breast Cancer in East Asian and European Population: A Two-Sample Mendelian Randomization

Choonghyun Ahn; Sangjun Lee; Sue K Park

doi:10.3390/cancers12113272

Causal Inference between Rheumatoid Arthritis and Breast Cancer in East Asian and European Population: A Two-Sample Mendelian Randomization

Cancers (Basel). 2020 Nov 5;12(11):3272. doi: 10.3390/cancers12113272.

Authors

Choonghyun Ahn^{1

2

3}, Sangjun Lee^{1

2

4}, Sue K Park^{1

4

5}

Affiliations

¹ Department of Preventive Medicine, Seoul National University College of Medicine, Seoul 03080, Korea.
² Department of Biomedical Science, Seoul National University Graduate School, Seoul 03080, Korea.
³ Tokyo University Hospital, Tokyo 1130033, Japan.
⁴ Cancer Research Institute, Seoul National University, Seoul 03080, Korea.
⁵ Convergence Graduate Program in Innovative Medicine Science, Seoul National University College of Medicine, Seoul 03080, Korea.

Abstract

Previous studies have been reported that the association between rheumatoid arthritis (RA) and breast cancer remains inconclusive. A two-sample Mendelian randomization (MR) analysis can reveal the potential causal association between exposure and outcome. A two-sample MR analysis using the penalized robust inverse variance weighted (PRIVW) method was performed to analyze the association between RA and breast cancer risk based on the summary statistics of six genome-wide association studies (GWAS) targeting RA in an East Asian population along with summary statistics of the BioBank Japan (BBJ), Breast Cancer Association Consortium (BCAC), and Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA) targeting breast cancer. We found that the direction of the effect of RA on breast cancer varied among GWAS-summary data from BBJ, BCAC, and CIMBA. Significant horizontal pleiotropy based on a penalized robust MR-Egger regression was observed only for BBJ and CIMBA BRCA2 carriers. As the results of the two-sample MR analyses were inconsistent, the causal association between RA and breast cancer was inconclusive. The biological mechanisms explaining the relationship between RA and breast cancer were unclear in Asian as well as in Caucasians. Further studies using large-scale patient cohorts are required for the validation of these results.

Keywords: Mendelian randomization; breast cancer; causal inference; genetics; rheumatoid arthritis.