We previously described diaryl trifluorothiazoline compound 1a (hereafter referred to as fluorizoline) as a first-in-class small molecule that induces p53-independent apoptosis in a wide range of tumor cell lines. Fluorizoline directly binds to prohibitin 1 and 2 (PHBs), two proteins involved in the regulation of several cellular processes, including apoptosis. Here we demonstrate that fluorizoline-induced apoptosis is mediated by PHBs, as cells depleted of these proteins are highly resistant to fluorizoline treatment. In addition, BAX and BAK are necessary for fluorizoline-induced cytotoxic effects, thereby proving that apoptosis occurs through the intrinsic pathway. Expression analysis revealed that fluorizoline induced the upregulation of Noxa and Bim mRNA levels, which was not observed in PHB-depleted MEFs. Finally, Noxa−/−/Bim−/− MEFs and NOXA-downregulated HeLa cells were resistant to fluorizoline-induced apoptosis. All together, these findings show that fluorizoline requires PHBs to execute the mitochondrial apoptotic pathway.

A new class of small molecules, with an unprecedented trifluorothiazoline scaffold, were synthesized and their pro-apoptotic activity was evaluated. With an EC50 in the low micromolar range, these compounds proved to be potent inducers of apoptosis in a broad spectrum of tumor cell lines, regardless of the functional status of p53. Fast structure-activity relationship studies allowed the preparation of the strongest apoptosis-inducing candidate. Using a high performance affinity purification approach, we identified prohibitins 1 and 2, key proteins involved in the maintenance of cell viability, as the targets for these compounds.

Ovarian cancer (OVCa) is the leading cause of death from gynecological malignancies. Although treatment for advanced OVCa has improved with the introduction of taxane-platinum chemotherapy, the majority of patients will develop resistance to the treatment, leading to poor prognosis. One of the causes of chemoresistance is the reduced ability to undergo apoptosis. Cisplatin is a genotoxic drug that leads cells to apoptosis through the activation of the p53 pathway. Defective signaling in this pathway compromises p53 function, and thus cisplatin does not induce apoptosis. A new group of nongenotoxic small molecules called Nutlins have been developed to inhibit p53-Mdm2 binding, inducing apoptosis in chemoresistant tumors through the activation of the p53 pathway. The wild-type p53 cisplatin-resistant ovarian cancer cell-line A2780cis was used to test the effect of Nutlin-3a (Nut3a) on apoptosis response. The results showed that Nut3a synergized with cisplatin, inducing cell-cycle arrest in G2/M and potentiating apoptotic cell death. Increased apoptosis was also induced in wild-type TP53 primary OVCa cultures by double cisplatin-Nut3a treatment. In conclusion, Nut3a appears to sensitize chemoresistant OVCa cells to cisplatin, inducing apoptosis. As increased response was generalized in primary tumors, this cisplatin-Nut3a combination could be useful for the treatment of patients harboring wild-type TP53 who do not respond to standard chemotherapy.Ovarian cancer (OVCa) kills~115,000 women annually worldwide. The majority of patients with OVCa are diagnosed with advanced disease and managed with surgical cytoreduction followed by platinum and taxane-based chemotherapy, 1 but the majority of them will eventually recur and die as a consequence of metastatic spread. Crystalline cis-dichlorodiammine platinum (II) [cisplatin (CDDP)] is the cytotoxic agent used as therapy, but it leads to chemoresistance, the largest obstacle in treating patients with recurrent disease. Multidrug resistance, DNA mismatch repair and alterations in the p53 pathway are examples of tumor-cell features that may lead to CDDP resistance. 2Defects in apoptosis are one of the mechanisms that can lead to chemoresistance. The p53 protein is recognized as an important cell-regulatory element that arrests the growth of cells containing damaged DNA. Cell-cycle control and activation of apoptosis appear to be tightly linked functions of p53. The importance of p53 in human malignances was highlighted by the detection of abnormal p53 in more than 50% of human cancers. 3,4 Mutations in TP53 are associated with a lack of response to high-dose CDDP therapy in OVCa patients. 5The short-lived protein p53 and its cellular levels are controlled by the rate at which it is degraded. Although several U3 ubiquitin ligases have been implicated in p53