In situ molecular profilling of the microenvironment of breast carcinoma

Sammanfattning: High stromal PDGF receptor B expression was shown to have strong prognostic value in a studyinvolving over 600 breast cancer patients however, the molecular role of the receptor in tumordevelopment remains unclear. In this project we studied the spatial distribution and expressionlevels of a panel genes and markers associated with PDGF signaling, in breast cancer tumormicroenvironment (TME) using a newly developed technique -in situ sequencing. The techniquerelies on padlock probes which we validated with corresponding RNA sequencing, microarray,and immunohistochemistry data. Our results showed that high PDGF receptor B mRNA colocalizedwith markers of two pathways, TGFβ and Hedgehog signaling; this suggests that theymight contribute to the PDGF-receptor B-driven tumor growth. We also showed that stromalPDGF signaling is stimulated predominantly by tumor cells. Finally, further expression profilingof each individual gene revealed that CXCL14 was mainly expressed in the stroma, ACTA2expression was enriched in the tumor/stroma boundary while the stem-cell marker, OCT3, wasexpressed in the interior of the tumor cells.