Abstract 1232: Paclitaxel induces immunogenic cell death in ovarian cancer via TLR4-independent and dependent pathways
Authors: Lau Tat-San , Chan Loucia Kit-Ying , Man Gene Chi-Wai , Kwong Joseph 
Published: August 2019

Immunogenic cell death refers to a phenomenon in which some of the cytotoxic chemotherapeutics kills the tumor cells and induces these dying cells to be immunogenic. The aim of this study is to investigate if the standard-of-care chemotherapy (carboplatin and paclitaxel) induces immunogenic cell death in ovarian cancer. We found that paclitaxel, but not carboplatin, induces multiple molecular determinants of immunogenic cell death (namely calreticulin exposure, ATP secretion, HMGB1 release, ANXA1 expression, and upregulation of CXCL10) in ID8 mouse ovarian cancer cells. By tumor vaccination assay in immunocompetent syngeneic mice, our results showed paclitaxel induces immunogenic cell death in the mice with ID8 ovarian tumor. Since toll-like receptor 4 (TLR4) is a receptor for paclitaxel, we generated isogenic derivatives of ID8 cells with Tlr4 knockout (KO) to investigate if paclitaxel induces immunogenic cell death is dependent on TLR4. Our results showed that the paclitaxel-induced molecular determinants of immunogenic cell death were diminished in the TLR4 KO clones when compared to wild-type controls. Moreover, the tumor vaccination assay showed that paclitaxel was not able to induce immunogenic cell death in mice with ovarian tumor with TLR4 KO. These results indicated that the paclitaxel requires TLR4 to induce immunogenic cell death. To explore the mechanisms of how paclitaxel induces immunogenic cell death through TLR4, we investigated the activation of PERK and phosphorylation of eIF2a in ER stress since they are the first two enumerate elements of the pathways that mediated calreticulin exposure in response to immunogenic anticancer chemotherapeutics. Our results, however, showed that paclitaxel induces activation of PERK and phosphorylation of eIF2a in ovarian cancer cells is independent on TLR4. We then investigate if paclitaxel induces SNARE-dependent exocytosis in mouse ovarian cancer cells because SNARE-dependent exocytosis is the final step of the pathways that mediated calreticulin exposure in immunogenic cell death. Our results showed that paclitaxel induces SNARE-dependent exocytosis of ATP-containing vesicles in mouse ovarian cancer cells via TLR4-mediated IKK2 activation. In summary, our results showed that paclitaxel induces immunogenic cell death in ovarian cancer through TLR4-independent and dependent pathways, in which paclitaxel-induced exocytosis is essential for the release of multiple molecular determinants of immunogenic cell death. Our results provide new evidence that the antitumor effect of paclitaxel occurs in part via activation of an immune response against cancer by inducing immunogenic cell death and provide a rationale for a new combination of paclitaxel and immunotherapies as an anticancer treatment.

Citation Format: Tat-San Lau, Loucia Kit-Ying Chan, Gene Chi-Wai Man, Joseph Kwong. Paclitaxel induces immunogenic cell death in ovarian cancer via TLR4-independent and dependent pathways [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1232.