1) decreased sensitivity to Tc cells (decreased antigen presentation, anti-apoptotic state is resistant to Tc)
2) suppress the immune response (induce T-cell destruction via FasL, secrete cytokines to prevent immune activity, neutralize complement, block NK cell recognition, attract Treg cells or other suppressive immune cells to tumour site, express PDL-1 that activates PD-1 immune checkpoint receptor on T-cells)
3) hide from immune response (immuno-privileged tissues, tumor architecture)
4) outpace the immune respone