PTGFRN and cancer: Fig 4C shows that, compared to the saporin IgG negative control, PTGFRN-positive human cancer cells treated with the 33B7-ADC resulted in a 61% ± 2% reduction of proliferation in A431 cells, and a 51% ± 6% reduction on proliferation in DAOY cells. No growth inhibitory effect of the 33B7-ADC was observed for the PTGFRN-negative cell lines (TOV-21G, MDA-MB-231). Fig 4D further indicates a dose-dependent inhibition of A431 cell proliferation.