Harnessing the immune response for the treatment of cancer by inducing immunogenic cell death through inhibition of a group II chaperonin

Abstract

Abstract Immunotherapy is a promising treatment for cancer but lacks broad application. One way to enhance immunotherapy is by inducing immunogenic cell death (ICD). ICD is characterized by a unique molecular signature, involving the release of molecules that sensitize cancer cells to killing by the immune system. However, most ICD-inducing agents are not effective at clinically relevant doses. We developed a novel cytotoxic peptide, CT20p, that is delivered to cells using nanoparticles (NPs), which causes regression of tumors in mice at nanomolar concentrations. CT20p-treated cancer cells upregulated markers characteristic of ICD, such as calreticulin (Crt) and HSP70. The intracellular target of CT20p is a group II chaperonin called chaperonin containing-TCP-1 (CCT) that is essential for the folding of actin, tubulin and other proteins like STAT3. The CCT complex is composed of eight subunits (CCT1-8). That CT20p cytotoxicity is driven by CCT was proven by inhibiting or overexpressing CCT2 in susceptible or resistant cells, respectively. Disruption of CCT activity by CT20p caused endoplasmic reticulum (ER) stress that initiated intracellular pathways, such as PERK and IRE-1, generating danger signals associated with ICD. As a result, increased phagocytosis of dying cancer cells and enhanced NK cell killing was observed. Importantly, normal epithelial cells, macrophages or NK cells were unaffected. Using the CRISPR-CAS9 system, the genes for CCT were edited. Loss of CCT2 altered the levels of other CCT subunits as well as client proteins such as STAT3, while increasing membrane-exposed Crt. These studies revealed that inhibiting CCT induces ICD to stimulate immune functions essential for generating a robust anti-cancer immune response.