by ecancer reporter Janet Fricker

Pancreatic ductal adenocarcinoma (PDAC) has been revealed to contain two types of tumour cells and two types of stromal cells, finds a study in Nature Genetics.

The findings, the US investigators suggest, could help oncologists to individualise treatment.

A hallmark of PDAC, a disease with five-year survival rates of only 4%, is extensive stromal involvement making it difficult to pinpoint the molecular changes that occur specifically in cancer cells.

For the study Jen Jen Yeh and colleagues, from UNC Lineberger Comprehensive Cancer Center, Chapel Hill, North Carolina, used a mathematical approach, known as ‘blind source separation’ to digitally separate tumour, stromal and normal gene expression.

The team explored gene expression patterns for 145 primary and 61 metastatic tumours, 17 cell lines, as well as 46 normal pancreatic samples and 88 samples of normal, non-cancerous tissue outside of the pancreas.

The results revealed two subtypes of pancreatic cancer tumours – ‘basal-like’ and ‘classical’.

They found that the two subtypes had markedly different outcomes – 44% of patients with the basal-like subtype lived one year following surgery compared to 70% with the classical subtype.

Furthermore, the team uncovered two subtypes of pancreatic stroma labelled ‘normal’ and ‘activated’.

Patients with the activated subtype had worse survival outcomes.

“Right now, we still treat pancreatic cancers as one entity, while for some other cancers, we personalize treatment based on an individual patient’s tumour genetics or other characteristics,” said Yeh.

“We believe these results will set the groundwork for future clinical trials, allow treatments to be assigned based on the subtypes, and guide the development of new therapies.”

Reference: R Moffitt, R Marayati, E Flate, et al. Virtual microdissection identifies distinct tumor-and stroma subtypes of pancreatic ductal adenocarcinoma. Nature Genetics. doi:10.1038/ng.3398