Breast tumour cell-induced down-regulation of type I collagen mRNA in fibroblasts
The tumour stroma in cases of ductal infiltrating carcinoma of the mammary gland contains substantial amounts of collagen type I trimer, besides the regular collagen types. Reconstituted collagen trimer consists of fibrils that are significantly thinner than reconstituted fibrils of type I collagen. The axial periodicity is somewhat longer due to widening of the c-d and d-e regions. Transmission EM of the tumours shows characteristic phenomena at the stromal-tumour cell junctions: frequent absence of a basal lamina and thin disordered collagen fibrils that show frequent direct contacts with tumour cells. On the basis of literature data concerning the interaction between stroma and epithelia under physiological and pathological conditions it is hypothesized that the interaction of collagen type I trimer fibrils with tumour cells is instrumental in augmenting tumour cell progression and that the trimer may provide contact guidance for invasive growth.