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

Modulation of autophagy and apoptosis can contribute to the anticancer effect of Abemaciclib/Celecoxib combination in colon cancer cells

Drug resistance and recurrence represent a great challenge in colorectal cancer management, highlighting the urgent need for novel therapeutics. Our objective is to evaluate the influence of Abemaciclib, Celecoxib, and their combination on both the autophagic and apoptotic machinery in an attempt to unravel the interplay between them in HCT-116 and Caco-2 cell lines. The MTT assay was used to assess the GI50 of the drugs. ELIZA was used to determine the protein levels of Beclin-1, LC3, Cox-2, and Bcl-2. Active Caspase-3 was determined by a colorimetric assay. Gene expression levels of ATG5, LC3, Beclin-1, and p62 were assessed by quantitative real-time PCR. In HCT-116 cells, the GI50s for Abemaciclib and Celecoxib were 15.86 and 92.67 μM, respectively, while for Caco-2 cells, the GI50s were 7.85 and 49.02 μM for Abemaciclib and Celecoxib, respectively. Upon treatment of HCT-116 and Caco-2 cells with Abemaciclib, Celecoxib, and their combinations, ATG5, p62, LC3, and Beclin-1 gene expression levels were up-regulated. The protein levels of Beclin-1, LC3, and Caspase-3 were significantly increased, while Bcl-2 was decreased in both cell lines due to single and combined treatments. Both drugs, either alone or in combination, decreased the migration ability of the cells in both cell lines. To conclude, the treatment protocol has the potential to induce cell cycle arrest, diminish the potentiality of cells for migration, and initiate apoptotic and autophagic cell death. Further research is recommended to unravel the potential antitumor effects of Abemaciclib/Celecoxib combination in different cancer types.

Deregulated E2F Activity as a Cancer-Cell Specific Therapeutic Tool

The transcription factor E2F, the principal target of the tumor suppressor pRB, plays crucial roles in cell proliferation and tumor suppression. In almost all cancers, pRB function is disabled, and E2F activity is enhanced. To specifically target cancer cells, trials have been undertaken to suppress enhanced E2F activity to restrain cell proliferation or selectively kill cancer cells, utilizing enhanced E2F activity. However, these approaches may also impact normal growing cells, since growth stimulation also inactivates pRB and enhances E2F activity. E2F activated upon the loss of pRB control (deregulated E2F) activates tumor suppressor genes, which are not activated by E2F induced by growth stimulation, inducing cellular senescence or apoptosis to protect cells from tumorigenesis. Deregulated E2F activity is tolerated in cancer cells due to inactivation of the ARF-p53 pathway, thus representing a feature unique to cancer cells. Deregulated E2F activity, which activates tumor suppressor genes, is distinct from enhanced E2F activity, which activates growth-related genes, in that deregulated E2F activity does not depend on the heterodimeric partner DP. Indeed, the ARF promoter, which is specifically activated by deregulated E2F, showed higher cancer-cell specific activity, compared to the E2F1 promoter, which is also activated by E2F induced by growth stimulation. Thus, deregulated E2F activity is an attractive potential therapeutic tool to specifically target cancer cells.

Cobimetinib Sensitizes Cervical Cancer to Paclitaxel via Suppressing Paclitaxel-Induced ERK Activation

<b><i>Introduction:</i></b> Chemoresistance remains the main cause of treatment failure in cervical cancer and novel therapeutic strategies are required. Cobimetinib, a potent yet selective inhibitor of MEK1 and 2, is currently used to treat melanoma clinically. In this work, we identified cobimetinib as a promising candidate for treating cervical cancer. <b><i>Methods:</i></b> The in vitro and in vivo efficacies of cobimetinib were examined using cervical cancer cell cultures and xenograft mouse model. Its combination with paclitaxel was analyzed using the combination index. Immunoblotting was performed on MAPK and ERK pathways. <b><i>Results:</i></b> Cobimetinib displays a potent anti-cervical cancer activity in a panel of cell lines regardless of cellular origin and HPV presence, and its combination with paclitaxel is synergistic in inhibiting cervical cancer cells. This is achieved by the growth inhibition and caspase-dependent apoptosis induction, through inhibiting MAPK/ERK activation. In addition, paclitaxel activates ERK in cervical cancer cells, and this can be reversed by cobimetinib. We finally confirm the efficacy of cobimetinib alone and its combination with paclitaxel in the cervical cancer xenograft mouse model. <b><i>Discussion/Conclusion:</i></b> Our preclinical findings will accelerate the initialization of clinical trials to use combination of cobimetinib and paclitaxel for treating cervical cancer. Our work also emphasizes the therapeutic value of targeting MAPK/ERK to overcome chemoresistance in cervical cancer.

Mechanisms of abemaciclib, a CDK4/6 inhibitor, induced apoptotic cell death in prostate cancer cells in vitro

The therapeutic effects of abemaciclib (ABE), an inhibitor of cyclin- dependent kinases (CDK) 4/6, on the proliferation of two types of prostate cancer (PC) cells were revealed. In this study, in vitro cytotoxic and apoptotic effects of ABE on metastatic castration-resistant prostate cancer (mCRPC) androgen receptor (AR) negative PC-3 and AR mutant LNCaP PC cells were analyzed with WST-1, Annexin V, cell cycle, reactive oxygen species (ROS), mitochondrial membrane potential, RT-PCR, western blot, and apoptosis protein array. ABE considerably inhibited the growth of PC cells in a dose-dependent manner (p<0.01) and caused significant apoptotic cell death through the suppression of CDK4/6-Cyclin D complex, ROS generation and depolarization of mitochondria membrane potential. However, PC-3 cells were more sensitive to ABE than LNCaP cells. Furthermore, the expression levels of several pro-apoptotic and cell cycle regulatory proteins were upregulated by ABE in especially PC-3 cells with the downregulation of apoptotic inhibitor proteins. Our results suggest that ABE inhibits PC cell growth and promotes apoptosis and thus ABE treatment may be a promising treatment strategy in especially mCRPC. Further preclinical and clinical studies should be performed to clarify the clinical use of ABE for the treatment of PC.

In vitro therapeutic effects of abemaciclib on triple-negative breast cancer cells

The cyclin-dependent kinases 4 and 6 have led to a significant improvement in the treatment of hormone-receptor-positive breast cancer. However, the therapeutic potential of abemaciclib in triple-negative breast cancer (TNBC) has not been definitively elucidated. Therefore, the objective of this study was to investigate abemaciclib mediated antiproliferative effects on MDA-MB-231 and MDA-MB-468 TNBC and MCF-10A cell line through annexin V, cell cycle, caspase-3, reverse transcription-polymerase chain reaction analysis, acridine orange, and DAPI staining, for the first time. In addition, the autophagy-related cell death was assessed by autophagy-LC3 assay and acidic vesicular organelles staining. Our findings demonstrated that abemaciclib treatment resulted in significant apoptotic cell death in TNBC cells via G0/G1 arrest, chromatin condensation, the upregulation of caspase-3 and Bax levels, and the downregulation of Bcl-2. However, the formation of a large number of cytoplasmic vacuoles was not associated with autophagy. Therefore, abemaciclib treatment could be an effective treatment for TNBC. However, further studies are needed to elucidate the molecular mechanism of abemaciclib-induced apoptotic as well as atypical cell death derived from lysosomes in TNBC.

Human Papillomavirus-Negative Cervical Cancer: A Comprehensive Review

Human papillomavirus (HPV) has been the leading cause of cervical cancer for over 25 years. Approximately 5.5–11% of all cervical cancers are reported to be HPV-negative, which can be attributed to truly negative and false-negative results. The truly HPV-negative cervical cancers are almost all cervical adenocarcinomas with unclear etiology. False HPV negativity can arise from histological misclassification, latent HPV infection, disruption of the targeting fragment, non-high risk HPV infection, and HPV testing methods. HPV-negative cervical cancers are often diagnosed at an advanced FIGO stage and have a poor prognosis; thus, the management of these cases requires greater attention.

Anisomycin sensitizes non-small-cell lung cancer cells to chemotherapeutic agents and epidermal growth factor receptor inhibitor via suppressing PI3K/Akt/mTOR

The poor outcomes in advanced non-small-cell lung cancer (NSCLC) necessitate new treatments. Recent studies emphasize anisomycin as a promising anti-cancer drug candidate. In this work, we systematically investigated the efficacy of anisomycin alone and its combination with the standard-of-care drugs in NSCLC. We showed that anisomycin inhibited growth, migration, and survival in NSCLC cells regardless of genetic mutation status, and to a greater extent than in normal lung epithelial cells. Isobologram analysis showed that the combination of anisomycin with cisplatin, paclitaxel, or gefitinib was synergistic in NSCLC but not normal lung cells. We further demonstrated that anisomycin inhibited NSCLC growth in mice. The combination of anisomycin with cisplatin was more effective than cisplatin alone and completely arrested NSCLC growth throughout the whole duration of treatment. JNK and p38 MAPK were not required for anisomycin's action. In contrast, anisomycin inhibits PI3K/Akt/mTOR pathway. Overexpression of constitutively active Akt reversed the pro-apoptotic effect of anisomycin. Our work demonstrates the selective anti-NSCLC activity of anisomycin via suppressing PI3K/Akt/mTOR. Our findings provide preclinical evidence to initialize the clinical trial of using anisomycin to sensitize NSCLC to current therapy.

Novel sequential treatment with palbociclib enhances the effect of cisplatin in RB-proficient triple-negative breast cancer

Background

Triple-negative breast cancer (TNBC) is a highly aggressive malignancy that lacks sensitivity to chemotherapy, endocrine therapy or targeted therapy. CDK4/6 inhibitors, combined with endocrine therapy, have been shown to be effective in postmenopausal women with HR-positive, HER2-negative advanced or metastatic breast cancer. Therefore, we investigated whether the CDK4/6 inhibitor palbociclib (PD) could enhance the effects of cisplatin (CDDP) on TNBC.

Methods

The effects of different drug regimens consisting of PD and CDDP on MDA-MB-231 and RB-knockdown MDA-MB-231 (sh-MDA-MB-231) cells were assessed in vitro and in vivo. MDA-MB-468 and RB-overexpressing MDA-MB-468 cells were used to assess the effect of the PD-CDDP regimens in vitro. Immunoblotting illustrated the role of the cyclin D1/RB/E2F axis signalling pathway.

Results

PD induced G1 phase cell cycle arrest in the MDA-MB-231 cell line. However, synchronous treatment with PD and CDDP for 24 h, treatment with PD for 24 h followed by CDDP and treatment with CDDP for 24 h followed by PD had no influence on MDA-MB-231 cell apoptosis. We further investigated the effect of PD or CDDP withdrawal on the effects of sequential treatment and found that PD treatment for 48 h followed by withdrawal for 48 h and subsequent CDDP treatment (PD-CDDP) significantly increased apoptosis and inhibited the cell viability and colony formation of MDA-MB-231 cells, while with other regimens, PD and CDDP had an additive or antagonistic response. The preferential use of PD increased DNA damage induced by CDDP, as measured through γH2AX immunofluorescence. These findings were not observed in sh-MDA-MB-231 cells, and experiments to assess cell function in MDA-MB-468 and RB-overexpressing MDA-MB-468 cells yielded similar results, which indicated that PD enhanced the sensitivity of TNBC cells to CDDP in an RB-dependent manner. In vivo, compared with single drug treatment, combination treatment inhibited tumour growth and Ki-67 expression in MDA-MB-231 xenograft models. Western blot analysis revealed that PD enhanced sensitivity to CDDP through the CDK4/6-cyclin D1-RB-E2F pathway.

Conclusions

Pre-treatment with PD synchronized the tumour cell cycle through the CDK4/6-cyclin D1-RB-E2F pathway, which increased the antitumour effect of CDDP. Thus, PD-CDDP might be an effective treatment for RB-proficient TNBC patients.