GPC1 and neoplasm: Probing the immunoprecipitates of Fig. 5b,c with antibodies to the α1(V) chain of col(V) showed α1(V) chains to have co-precipitated with α3(V) chains and GPC1 (Fig. 5b,c), consistent with the probability that tumour α3(V) chains bind GPC1 in the context of α1(V)α2(V)α3(V) heterotrimers.