Autocrine Transforming Growth Factor-β (TGFβ) modulates the 120 kD and 105 kD Retinoblastoma (RB) protein species in CBS colon carcinoma cells as revealed by an anti-sense TGFβ1 expression vector

Specific RB protein species modulated by autocrine TGFβ are unknown. CBS NEO (with autocrine TGFβ) and antisense TGFβ1 transfected CBS RSVAS cells were compared for mitogenesis and RB species modulation. Significantly, high MW (120, 130 kD) were abundant relative to low MW (116, 110, 105 kD combined) RB species. CBS NEO required growth factors (GF) for maximal DNA synthesis (14-fold). 120 kD and 105 kD were significantly modulated in CBS NEO-GF. Nutrients (N) were sufficient to maximally stimulate CBS RSVAS (8-fold). 130 kD and 116-110 low MW species were moderately induced by both N (CBS RSVAS-N) and GF (CBS NEO-GF), independent of autocrine TGFβ. In conclusion, autocrine TGFβ (CBS) has a role in modulation of 120 kD and 105 kD RB species which may play a role in the inhibitory action of autocrine TGFβ pathway.