Current
ovarian cancer maintenance
therapy is limited by toxicity and no proven impact on overall survival. To study a maintenance strategy targeted at missense mutant p53, we hypothesized that the release of mutant p53 from
mortalin inhibition by the
SHetA2 drug combined with reactivation of mutant p53 with the PRIMA-1MET
drug inhibits growth and
tumor establishment synergistically in a mutant-p53 dependent manner. The
Cancer Genome Atlas (TCGA) data and serous ovarian
tumors were evaluated for TP53 and HSPA9/
mortalin status.
SHetA2 and PRIMA-1MET were tested in
ovarian cancer cell lines and fallopian tube secretory epithelial cells using isobolograms, fluorescent cytometry, Western blots and ELISAs. Drugs were administered to mice after peritoneal injection of MESOV mutant p53
ovarian cancer cells and prior to
tumor establishment, which was evaluated by logistic regression. Fifty-eight percent of TP53 mutations were missense and there were no
mortalin mutations in TCGA high-grade serous
ovarian cancers.
Mortalin levels were sequentially increased in serous benign, borderline and
carcinoma tumors.
SHetA2 caused p53 nuclear and mitochondrial accumulation in
cancer, but not in healthy, cells. Endogenous or exogenous mutant p53 increased
SHetA2 resistance. PRIMA-1MET decreased this resistance and interacted synergistically with
SHetA2 in mutant and wild type p53-expressing cell lines in association with elevated
reactive oxygen species/
ATP ratios.
Tumor-free rates in animals were 0% (controls), 25% (PRIMA1MET ), 42% (
SHetA2) and 67% (combination).
SHetA2 (p = 0.004) and PRIMA1MET (p = 0.048) functioned additively in preventing
tumor development with no observed toxicity. These results justify the development of
SHetA2 and PRIMA-1MET alone and in combination for
ovarian cancer maintenance
therapy.