The knocking down of Cx43 or the inhibition of Cx43 channels using the Cx43 mimetic peptide gap27 leads to a decrease in this intercellular communication and, subsequently, to the GrzmB activity in the melanoma target cells, suggesting that Cx43-GJ formation is necessary for an efficient CTL-mediated tumor cell killing. The gene discussed is GJA1; the disease is neoplasm.