TY - JOUR AB - Cancer cells have developed numerous strategies to maintain their proliferative capacity and to withstand different kinds of stress. The mitochondrial stress‑70 protein named glucose regulated protein 75 (GRP75), also known as mortalin, is an intriguing cancer pro‑survival factor. It is constitutively expressed in normal tissues but is upregulated in many tumors, and was shown to be a cancer prognostic biomarker. Mortalin is an inhibitor of complement‑dependent cytotoxicity (CDC) and may therefore protect cells from antibody‑based immunotherapy. To target mortalin for cancer therapy, our laboratory designed several mortalin mimetic peptides with sequences predicted to be involved in mortalin binding to its client proteins. The peptides were synthesized with a C‑terminal transactivator of transcription sequence. By using cell death methodologies, the mechanism of action of the mortalin mimetic peptides on cancer cells was studied. Two peptides in particular, Mot‑P2 and Mot‑P7, were found to be highly toxic to lymphoma and ovarian, breast and prostate carcinoma cells. The analysis of their mode of action revealed that they may induce, within minutes, plasma membrane perturbations and mitochondrial stress. Furthermore, Mot‑P2 and Mot‑P7 activated necrotic cell death, leading to plasma membrane perforation, mitochondrial inner membrane depolarization and decrease in ATP level. In addition, Mot‑P7, but not Mot‑P2, required extracellular calcium ions to fully mediate cell death and was partially inhibited by plasma membrane cholesterol. At sub‑toxic concentrations, the two peptides moderately inhibited cancer cell proliferation and blocked cell cycle at G2/M. Both peptides may bind intracellularly to mortalin and/or a mortalin‑binding protein, hence knocking down mortalin expression reduced cell death. Combining treatment with Mot‑P2 or Mot‑P7 and CDC resulted in increased cell death. This study identified highly cytotoxic mortalin mimetic peptides that may be used as monotherapy or combined with complement‑activating antibody therapy to target mortalin for precision cancer therapy. AD - Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel Department of Biochemistry and Molecular Biology, Medical University of Lublin, Lublin 20-093, Poland Institute of Hematology, Davidoff Cancer Center, Rabin Medical Center - Beilinson Hospital, Petach Tikva 49100, and the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel AU - Jubran,Ritta AU - Saar-Ray,Moran AU - Wawruszak,Anna AU - Ziporen,Lea AU - Donin,Natalie AU - Bairey,Osnat AU - Fishelson,Zvi DA - 2020/10/01 DO - 10.3892/ijo.2020.5101 EP - 1026 IS - 4 JO - Int J Oncol KW - mortalin peptides complement-dependent cytotoxicity cell death mitochondria PY - 2020 SN - 1019-6439 1791-2423 SP - 1013 ST - Mortalin peptides exert antitumor activities and act as adjuvants to antibody-mediated complement-dependent cytotoxicity T2 - International Journal of Oncology TI - Mortalin peptides exert antitumor activities and act as adjuvants to antibody-mediated complement-dependent cytotoxicity UR - https://doi.org/10.3892/ijo.2020.5101 VL - 57 ER -