RT-PCR-assisted quantification of type I IFN responses in irradiated cancer cells

It is now clear that radiation therapy (RT) can be delivered in doses and according to fractionation schedules that actively elicit immunostimulatory effects. While such effects are often sufficient to drive potent anticancer immunity culminating with systemic disease eradication, the immunostimulatory activity of RT stands out as a promising combinatorial partner for bona fide immunotherapeutics including immune checkpoint inhibitors (ICIs). Accumulating preclinical and clinical evidence indicates that the secretion of type I interferon (IFN) by irradiated cancer cells is a sine qua non for RT to initiate ICI-actionable tumor-targeting immune responses. Here, we detail a simple protocol to quantitatively assess type I IFN responses in irradiated mouse hormone receptor (HR)⁺ TS/A cells by RT-PCR. With minimal variations, the same technique can be straightforwardly adapted to quantify type I IFN-associated transcriptional responses in a variety of human and mouse cancer cells maintained in vitro.