However, in Cldn14-heterozygous mice (with loss of only one copy of Cldn14) we found the following major phenotypes: (1) disruption of cell-cell junctions in tumour blood vessel; (2) abnormal tumour blood vessel basement membrane organisation and reduced supporting cell association; (3) increased intratumoural leakage and decreased tumour hypoxia; (4) enhanced tumour angiogenesis but no significant difference in the proportion of lumenated tumour blood vessels; (5) no effect on syngeneic tumour growth and (5) increased endothelial cell proliferation in vivo, ex vivo and in vitro. Here, CLDN14 is linked to neoplasm.