COL3A1 and skin neoplasm: Hence, we analyzed the expression of selected ECM components in skin tumors by qRT-PCR and found that the mRNA levels of α1 chains of collagen I (Col1a1) and III (Col3a1) and Tnc were significantly higher in Itga11+/+ papillomas than in Itga11−/− papillomas (Figure 4A).