PTPRC and colorectal carcinoma: Because the frequency of NK cells, defined as CD45+CD56+CD3− cells, and CD16+ NK cells was indeed low (0.80% (SEM 0.03) and 0.19% (SEM: 0.06) of total CD45+ leukocytes, respectively) (Figure 6D,E), we tested the activity of C-7 not only in 7-day cultures of patient-derived dissociated CRC tumor cells (not selected for specific EGFR expression levels) alone but also in co-cultures of CRC tumor cells and autologous patient-derived PBMC.