Melanoma cells downregulate keratinocyte Dsg1 through paracrine signaling. Primary human keratinocytes were treated for 24 h with conditioned media from melanocytes (MC) or the melanoma cell lines WM1341D (labeled as 1341D in figures), WM1366 (labeled as 1366 in figures), WM3211 (labeled as 3211 in figures), YUMAC, and 501mel, and RNA or protein was collected. (A and B) RT-PCR (A) and Western blots (B) were performed for Dsg1, Ecad, and Dsg3. Significantly lower mRNA and protein expression of Dsg1, but not Ecad or Dsg3, was observed. n = 3. Mean ± SEM depicted. *P < 0.05; **P < 0.01; ***P < 0.001. One-way ANOVA. (C) Melanocytes or WM1341D melanoma cells were seeded with normal primary keratinocytes and grown as 3D organotypic raft cocultures for up to 10 d. Paraffin sections were costained for Dsg1 or Ecad and Mel-A. The dashed line indicates the basement membrane. (D) Pixel intensities were determined and the ratio of proximal to distant intensities plotted. A significant decrease in Dsg1, but not Ecad, intensity proximal to the WM1341D lesions was observed. Mean ± SEM depicted. n = 6. *P < 0.05, Student’s t test. Source data are available for this figure: SourceData F2.