Study of fibronectin mRNA in human laryngeal and ectocervical carcinomas by IN SITU hybridization and image analysis

The expression of fibronectin (FN) mRNA was studied in histological sections of surgical biopsies from human laryngeal and ectocervical invasive carcinomas of different grading stages by in situ hybridization and image analysis. This approach made it possible to identify the cell types synthesizing FN mRNA in the tissue sections and to compare semi‐quantitatively the FN mRNA levels expressed in the different specimens. The carcinoma cells synthesized low levels of FN mRNA, comparable to those detected in control epithelia and connective‐tissue fibroblasts. Well‐differentiated (G1) laryngeal and ectocervical carcinomas induced the synthesis of FN mRNA—to levels 7 to 13 times higher than in control connective tissues—in the stromal fibroblasts surrounding the tumors. In carcinoma samples analysed, the amount of FN mRNA detected in the stroma decreased in relation to tumor grading (from G1 to G3) and the stromal destruction. FN mRNA was not detectable in the endothelial cells of venules while it was present in large amounts in those surrounding the capillaries present in the stroma. These data indicate that FN, usually observed around carcinomas, is produced by stromal fibroblasts, which are induced to express FN mRNA, presumably in response to diffusible factors produced by the tumor cells, and/or by endothelial cells of the infiltrating capillary vessels. The induction of FN mRNA, inversely proportional to the tumor grading, may be useful in evaluating the invasion potential of the tumor. © 1992 Wifey‐Liss, Inc.