GJA1 and neoplasm: Together with the tumor-suppressing proteins such as CALR, ENO1, HSP, MSN, and UBC, which were enriched in tumor-suppressive CM, six recombinant proteins, such as HISTONE H4, PPIB, GJA1, CPE, S100A11, and PCOLCE, were identified as extracellular tumor-suppressing proteins.