COL1A1 and melanoma: Although it remains unclear whether COL1A1 is secreted in the form of a homotrimer or heterotrimer and what arrangement it takes, similar bipolar cellular morphology and restricted cell motility were observed when melanoma cells were cultured on an exogenous type I collagen matrix.[62, 63] Therefore, we speculate that when trapped by type I collagen, cells extend in a unipolar manner back and forth, producing a cellular morphology similar to that of Schwann cells cultured in vitro.