Influence of Extracellular Acidosis on Matrix Protein Homeostasis in Tumour Cells and Fibroblasts

Pathogenesis of tumour development comprises among others changes of its microenvironment that can be caused by tumour cells or stroma cells like fibroblasts and include extracellular acidosis. Acidosis then may have impact on tumour cells, fibroblasts and their cross-talk, leading for example to an altered matrix protein homeostasis. The mentioned changes can support tumour progression. In the present study the influence of metabolic acidosis on matrix proteins in tumour cells, fibroblasts and their co-culture was evaluated. The experiments were performed in rat tumour cells (AT-1), normal rat kidney fibroblasts (NRKF) and their co-culture. Cells were exposed to acidic media for up to 48 h. Changes of collagen I and fibronectin were measured: mRNA content by RT-PCR, intracellular protein by immune blot and extracellular proteins by direct ELISA. In AT-1 cells acidosis led to decreased secretion of collagen I and fibronectin. The mRNA of both was unchanged and intracellular collagen I was decreased. In NRKF extracellular collagen I was increased and fibronectin unchanged. The collagen I and fibronectin mRNA was unchanged and intracellular collagen I was increased. In the co-culture media, collagen I changes vanished and fibronectin was decreased. In co-culture the mRNA content of collagen I and fibronectin in AT-1 was unchanged but both were increased in NRKF. In AT-1 and NRKF mono-culture extracellular matrix protein changes seem to be the result of posttranscriptional regulation.