Fundamental & Clinical Pharmacology

Repurposing Asparaginase Therapy to Target Cisplatin‐Resistant Cancer Cells

ABSTRACT Background Cisplatin and its derivatives remain a cornerstone in the treatment of solid malignancies. Resistance is a major factor limiting their clinical utility. Objectives In the present study, we set out to interrogate therapeutic approaches to target cisplatin‐resistant cancer cells. We focused on therapies exploiting metabolic pathways that are altered in drug‐resistant cells. We sought to find an existing therapy that has monotherapy efficacy against cisplatin‐resistant cancer cells that can also re‐sensitize to cisplatin. Methods We used lung and ovarian cancer cell lines with acquired resistance to cisplatin together with drug sensitivity assays, conducted both with monotherapies and cisplatin combinations. Results We show that cancer cell lines with acquired resistance to cisplatin have altered levels of enzymes involved in glutamine metabolism, which can result in differential sensitivity to targeted agents. We show that expression of one of these enzymes—the glutamate‐cystine antiporter SLC7A11, up‐regulated 6‐fold in a cisplatin‐resistant lung cancer cell line—has potential prognostic significance in lung cancer but not ovarian cancer. After identifying a common dependency of cisplatin‐resistant cancer cells upon extracellular glutamine, we then evaluate the utility of the long‐standing anti‐leukemic therapy asparaginase (ASNase)—which possesses both asparaginase and glutaminase activity—as a potential approach. We show ASNase preferentially inhibits the proliferation of cisplatin‐resistant cancer cells and can potentially re‐sensitize these cells to cisplatin. Conclusions Our results underpin the prevalence of altered metabolism in cisplatin‐resistant cells and highlight the potential utility of re‐purposing ASNase to target these cells, warranting further investigation.

Hydrogen Sulfide Treatment Enhanced Paclitaxel's Anticancer Effect on the ID8 Murine Epithelial Ovarian Cancer Cell Line

ABSTRACT Background Paclitaxel is a potent agent against ovarian cancer. Hydrogen sulfide (H 2 S) is of particular interest in cancer treatment research. It is known that H 2 S has apoptotic and antiproliferative effects. Objectives We aimed to examine the potential effects of H 2 S donor NaHS and paclitaxel, both individually and when co‐administered, on the ID8 murine epithelial ovarian cancer cell line. Methods We examined the effects of the co‐administration of paclitaxel and NaHS on cell viability, cytotoxicity, reactive oxygen species (ROS) levels, mitochondrial membrane potential (MMP), apoptosis, and proliferation in the ID8 ovarian cancer cell line. 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide and lactate dehydrogenase tests were performed to ascertain the effect of NaHS and paclitaxel on cell viability and cytotoxicity. Caspase 3/7 levels were quantified in order to detect whether apoptosis is caspase dependent. Quantitative real‐time polymerase chain reaction (qPCR) method was used to ascertain relative mRNA levels of Bcl‐2, Bcl‐xL, Bax, and Bak genes. Results The viability of ID‐8 cells showed a significant reduction following the co‐administration of paclitaxel and NaHS, compared to the paclitaxel administration only. The results of qPCR analysis demonstrated significant alterations in the Bcl‐2, Bcl‐xL, Bax, Bak, Casp3, Casp8, and Casp9 genes' mRNA levels following cotreatment. In contrast to paclitaxel alone, its co‐administration with NaHS resulted in increased apoptosis and decreased ROS levels. The presence of NaHS has been observed to enhance the apoptotic impact of paclitaxel by amplifying the decline in MMP. Conclusion These data indicate that co‐administration of H 2 S with paclitaxel could be useful as a potential agent in the treatment of ovarian cancer. We found that the presence of H 2 S enhanced the antitumor efficacy of paclitaxel.

The cyclin‐dependent kinase inhibitor AT7519 augments cisplatin's efficacy in ovarian cancer via multiple oncogenic signaling pathways

AbstractAlthough cisplatin is the most active drug for the treatment of ovarian cancer, majority of patients develop resistance and ultimately relapse. Enhancing the efficacy of cisplatin could represent a promising strategy to improve the clinical outcome of patients with ovarian cancer. AT7519 is a multitargeted cyclin‐dependent kinase (CDK) inhibitor and displays potent anticancer activities. In this work, we show that the combination of AT7519 with cisplatin is much more superior to cisplatin alone in inhibiting ovarian cancer. AT7519 at nanomolar concentrations inhibits proliferation and migration and induces apoptosis of multiple ovarian cancer cell lines. In contrast, AT7519 at the same concentrations either does not affect survival or is significantly less effective in inhibiting proliferation and migration in normal ovarian cells and fibroblast cells. AT7519 significantly augments the inhibitory effects of cisplatin in ovarian cancer cells in a dose‐dependent manner. Mechanistic studies suggest that AT7519 (i) inhibits proliferation via decreasing activities of CDK1 and 2, and via inhibiting RNA transcription; (ii) inhibits migration via suppressing epithelial–mesenchymal transition (EMT); and (iii) induces apoptosis via decreasing Mcl‐1 and increasing Bim in ovarian cancer cells. Using a human ovarian cancer xenograft mouse model, we confirm the in vivo efficacy of AT7519 alone, and the synergistic effects of AT7519 and cisplatin in combination, at doses that cause minimal toxicity in mice. Our findings provide systematic preclinical evidence to support the initialization of clinical trials of the AT7519 and cisplatin combination for the treatment of ovarian cancer.

Therapeutic targeting of DNA damage repair pathways guided by homologous recombination deficiency scoring in ovarian cancers

AbstractThe susceptibility of cells to DNA damage and their DNA repair ability are crucial for cancer therapy. Homologous recombination is one of the major repairing mechanisms for DNA double‐strand breaks. Approximately half of ovarian cancer (OvCa) cells harbor homologous recombination deficiency (HRD). Considering that HRD is a major hallmark of OvCas, scholars proposed HRD scoring to evaluate the HRD degree and guide the choice of therapeutic strategies for OvCas. In the last decade, synthetic lethal strategy by targeting poly (ADP‐ribose) polymerase (PARP) in HR‐deficient OvCas has attracted considerable attention in view of its favorable clinical effort. We therefore suggested that the uses of other DNA damage/repair‐targeted drugs in HR‐deficient OvCas might also offer better clinical outcome. Here, we reviewed the current small molecule compounds that targeted DNA damage/repair pathways and discussed the HRD scoring system to guide their clinical uses.

FKA‐A NPs enhances PTX‐A NPs efficacy to suppress ovarian cancer via regulating Skp2/YAP pathway

AbstractRecurrence and distant metastasis after paclitaxel (PTX)‐based chemotherapy in ovarian cancer (OC) patients remains a clinical obstacle. Flavokawain A (FKA) is a novel chalcone from kava plant that can induce G2/M arrest and inhibit invasion and metastasis in different tumor cells. In this study, we examined the effects and the molecular mechanism of sodium aescinate (Aes)‐stabilized nanoparticles FKA‐A NPs in enhancing the efficacy of PTX‐A NPs in vitro and in vivo. We showed that FKA‐A NPs combined with PTX‐A NPs notably inhibited the proliferation and migration and reduced the expression of EMT‐related markers in OCs. YAP nuclear translocation and its downstream signaling pathway were remarkably activated after PTX‐A NPs treatment in OCs. FKA‐A NPs obviously inhibited YAP nuclear translocation and reduced the transcriptional activity of YAP target genes. Simultaneously, FKA‐A NPs dose and time dependently inhibited Skp2 expression in A2780 and Skov3 cells. In contrast, overexpression of Skp2 significantly attenuated the inhibition of FKA‐A NPs on YAP nuclear translocation. In OC homograft mice, treatment with FKA‐A NPs and PTX‐A NPs significantly suppressed the growth of homograft tumor compared with PTX‐A NPs but did not decrease mice's body weight. In summary, we demonstrate that FKA‐A NPs enhance the efficacy of PTX‐A NPs against OCs in vitro and in vivo via reducing Skp2 expression, thus suppressing YAP nuclear translocation and activity of its target genes.

Abemaciclib sensitizes HPV‐negative cervical cancer to chemotherapy via specifically suppressing CDK4/6‐Rb‐E2F and mTOR pathways

ABSTRACTCervical cancer is the second most common malignancy in women, and the novel therapeutic treatment is needed. Abemaciclib is a FDA‐approved drug for breast cancer treatment. In this work, we identified that abemaciclib has potent anti‐cervical cancer activity. We demonstrate that abemaciclib is the most effective drug against human papillomavirus (HPV)‐negative cervical cancer cells compared to ribociclib and palbociclib, with its IC50 at nanomolar concentration range. This is achieved by the inhibition of proliferation and induction of apoptosis, through specifically suppressing CDK4/6‐Rb‐E2F and mTOR pathways by abemaciclib in HPV‐negative cervical cancer cells. Of note, the combination of abemaciclib with paclitaxel and cisplatin at sublethal concentration results in much greater efficacy than chemotherapy alone. In addition, we confirm the efficacy of abemaciclib and its combination with paclitaxel or cisplatin at the doses that are not toxic to mice in HPV‐negative cervical cancer xenograft mouse model. Interestingly, we show that abemaciclib and other CDK4/6 inhibitors are not effective in targeting HPV‐positive cervical cancer cells, and this is likely to be associated with the high p16 and low Rb expression in HPV‐positive cervical cancer cells. Our work is the first to provide the preclinical evidence to demonstrate the potential of abemaciclib for the treatment of HPV‐negative cervical cancer. The mechanism analysis highlights the therapeutic value of inhibiting CDK4/6 in HPV‐negative but not HPV‐positive cervical cancer.

Simvastatin enhances chemotherapy in cervical cancer via inhibition of multiple prenylation‐dependentGTPases‐regulated pathways

AbstractAberrant activation ofGTPases is common in cervical cancer, and their proper biological functions largely depend on a post‐translational modification termed prenylation. Simvastatin is a cholesterol‐lowering drug via inhibitingHMG‐CoA reductase, thereby inhibiting protein prenylation. In this study, we show that simvastatin selectively inhibits proliferation and induces apoptosis in cervical cancer cells while sparing normal cervical epithelial cells. This is achieved by depleting geranylgeranyl pyrophosphate, inhibiting prenylation, decreasingGTPases activities and suppressing the activation of downstream Ras and RhoA signaling. The combination of simvastatin and paclitaxel remarkably augments in vitro as well as in vivo efficacy of either drug alone in cellular system and xenograft mouse model. Importantly, we show that cervical cancer cells have higher level ofHMG‐CoA reductase and elevated activities ofGTPases, suggesting that cervical cancer cells may be more dependent on prenylation than normal cervical epithelial cells. This might explain the selective inhibitory effects of simvastatin in cervical cancer. Since simvastatin is already available for clinic use, these results suggest that simvastatin is a promising drug candidate in combination with chemotherapy for the treatment of cervical cancer. Our findings also emphasize the therapeutic value of prenylation inhibition and provide preclinical evidence to evaluate prenylation‐targeted drugs in cervical cancer.