# Evidence that extra copies of chromosome 1q play a role in the early phases of pancreatic neoplasia

## TL;DR

This study shows that extra copies of a specific part of chromosome 1q, containing γ-secretase genes, are linked to early stages of pancreatic cancer development.

## Contribution

The study identifies γ-secretase genes on chromosome 1q as candidate oncogenes activated early in pancreatic neoplasia.

## Key findings

- Gains of 1q occurred in 39.8% of pancreatic ductal adenocarcinomas.
- Two ~3-megabase regions on 1q containing NCSTN and PSEN2 were frequently gained in high-grade precancerous lesions.
- Extra copies of NCSTN and PSEN2 were found in 49% of high-grade lesions but only 6% of low-grade lesions.

## Abstract

We searched for oncogenes activated by copy number increases using whole-genome sequencing data of 535 pancreatic ductal adenocarcinomas (PDACs). We found that gains of 1q were the second most common gain, occurring in 213 (39.8%) of PDACs. Single-cell analysis via fluorescence in situ hybridization on 33 cancers confirmed these results. A portion of 1q, rather than the entire 1q arm, was gained in 75 (14.0%) PDACs, allowing us to pinpoint two ~3-megabase regions of 1q that were nearly always gained. These two regions contained NCSTN and PSEN2, genes that code two subunits of the γ-secretase complex. Evaluation of 267 precancerous lesions revealed that extra copies of NCSTN and PSEN2 were common (49%) in noninvasive neoplasms (high-grade pancreatic intraepithelial neoplasms), which are at relatively high risk for progression to PDACs, but uncommon (6%) in low-grade pancreatic intraepithelial neoplasia lesions, which have low malignant potential. We hypothesize that γ-secretase genes are genetically activated oncogenes in the early phases of pancreatic neoplasia.

Copy number increases of the γ-secretase genes on 1q were identified as candidate oncogenes in pancreatic neoplasms.