Antagonizing the spindle assembly checkpoint silencing enhances paclitaxel and Navitoclax-mediated apoptosis with distinct mechanistic

A novel HDAC6 inhibitor interferes microtubule dynamics and spindle assembly checkpoint and sensitizes cisplatin-induced apoptosis in castration-resistant prostate cancer

BACKGROUND

Metastatic castration-resistant prostate cancer (CRPC), the most refractory prostate cancer, inevitably progresses and becomes unresponsive to hormone therapy, revealing a pressing unmet need for this disease. Novel agents targeting HDAC6 and microtubule dynamics can be a potential anti-CRPC strategy.

METHODS

Cell proliferation was examined in CRPC PC-3 and DU-145 cells using sulforhodamine B assay and anchorage-dependent colony formation assay. Flow cytometric analysis of propidium iodide staining was used to determine cell-cycle progression. Cell-based tubulin polymerization assay and confocal immunofluorescence microscopic examination determine microtubule assembly/disassembly status. Protein expressions were determined using Western blot analysis.

RESULTS

A total of 82 novel derivatives targeting HDAC6 were designed and synthesized, and Compound 25202 stood out, showing the highest efficacy in blocking HDAC6 (IC50, 3.5 nM in enzyme assay; IC50, 1.0 μM in antiproliferative assay in CRPC cells), superior to tubastatin A (IC50, 5.4 μM in antiproliferative assay). The selectivity and superiority of 25202 were validated by examining the acetylation of both α-tubulin and histone H3, detecting cell apoptosis and HDACs enzyme activity assessment. Notably, 25202 but not tubastatin A significantly decreased HDAC6 protein expression. 25202 prolonged mitotic arrest through the detection of cyclin B1 upregulation, Cdk1 activation, mitotic phosphoprotein levels, and Bcl-2 phosphorylation. Compound 25202 did not mimic docetaxel in inducing tubulin polymerization but disrupted microtubule organization. Compound 25202 also increased the phosphorylation of CDC20, BUB1, and BUBR1, indicating the activation of the spindle assembly checkpoint (SAC). Moreover, 25202 profoundly sensitized cisplatin-induced cell death through impairment of cisplatin-evoked DNA damage response and DNA repair in both ATR-Chk1 and ATM-Chk2 pathways.

CONCLUSION

The data suggest that 25202 is a novel selective and potent HDAC6 inhibitor. Compound 25202 blocks HDAC6 activity and interferes microtubule dynamics, leading to SAC activation and mitotic arrest prolongation that eventually cause apoptosis of CRPC cells. Furthermore, 25202 sensitizes cisplatin-induced cell apoptosis through impeding DNA damage repair pathways.

Maximizing Anticancer Response with MPS1 and CENPE Inhibition Alongside Apoptosis Induction

Antimitotic compounds, targeting key spindle assembly checkpoint (SAC) components (e.g., MPS1, Aurora kinase B, PLK1, KLP1, CENPE), are potential alternatives to microtubule-targeting antimitotic agents (e.g., paclitaxel) to circumvent resistance and side effects associated with their use. They can be classified into mitotic blockers, causing SAC-induced mitotic arrest, or mitotic drivers, pushing cells through aberrant mitosis by overriding SAC. These drugs, although advancing to clinical trials, exhibit unsatisfactory cancer treatment outcomes as monotherapy, probably due to variable cell fate responses driven by cyclin B degradation and apoptosis signal accumulation networks. We investigated the impact of inhibiting anti-apoptotic signals with the BH3-mimetic navitoclax in lung cancer cells treated with the selective CENPE inhibitor GSK923295 (mitotic blocker) or the MPS1 inhibitor BAY1217389 (mitotic driver). Our aim was to steer treated cancer cells towards cell death. BH3-mimetics, in combination with both mitotic blockers and drivers, induced substantial cell death, mainly through apoptosis, in 2D and 3D cultures. Crucially, these synergistic concentrations were less toxic to non-tumor cells. This highlights the significance of combining BH3-mimetics with antimitotics, either blockers or drivers, which have reached the clinical trial phase, to enhance their effectiveness.

Perspectives and mechanisms for targeting mitotic catastrophe in cancer treatment

Mitotic catastrophe is distinct from other cell death modes due to unique nuclear alterations characterized as multi and/or micronucleation. Mitotic catastrophe is a common and virtually unavoidable consequence during cancer therapy. However, a comprehensive understanding of mitotic catastrophe remains lacking. Herein, we summarize the anticancer drugs that induce mitotic catastrophe, including microtubule-targeting agents, spindle assembly checkpoint kinase inhibitors, DNA damage agents and DNA damage response inhibitors. Based on the relationships between mitotic catastrophe and other cell death modes, we thoroughly evaluated the roles played by mitotic catastrophe in cancer treatment as well as its advantages and disadvantages. Some strategies for overcoming its shortcomings while fully utilizing its advantages are summarized and proposed in this review. We also review how mitotic catastrophe regulates cancer immunotherapy. These summarized findings suggest that the induction of mitotic catastrophe can serve as a promising new therapeutic approach for overcoming apoptosis resistance and strengthening cancer immunotherapy.

Inhibition of non-homologous end joining mitigates paclitaxel resistance resulting from mitotic slippage in non-small cell lung cancer

Mitotic slippage, which enables cancer cells to bypass cell death by transitioning from mitosis to the G1 phase without undergoing normal cytokinesis, is one likely mechanism of paclitaxel (PTX) resistance. DNA double-strand breaks (DSBs) in the G1 phase are mainly repaired through non-homologous end joining (NHEJ). Therefore, inhibiting NHEJ could augment the PTX-induced cytotoxicity by impeding the repair of PTX-induced DSBs during the G1 phase following mitotic slippage. We aimed to evaluate the effects of NHEJ inhibition on mitotic slippage after PTX treatment in non-small cell lung cancer (NSCLC). H1299, A549, H1975, and H520 NSCLC cell lines were employed. In addition, A-196 and JQ1 were used as NHEJ inhibitors. H1299 cells were PTX-resistant and exhibited an increased frequency of mitotic slippage upon PTX treatment. NHEJ inhibitors significantly augmented the PTX-induced cytotoxicity, DSBs, and apoptosis in H1299 cells. The newly generated PTX-resistant cells were even more prone to mitotic slippage following PTX treatment and susceptible to the combined therapy. Docetaxel further demonstrated synergistic effects with the NHEJ inhibitor in PTX-resistant cells. NHEJ inhibition may overcome intrinsic or acquired PTX resistance resulting from mitotic slippage by synergistically increasing the cytotoxic effects of antimitotic drugs in NSCLC.

Role of PCK2 in the proliferation of vascular smooth muscle cells in neointimal hyperplasia

Vascular smooth muscle cell (VSMC) proliferation is a hallmark of neointimal hyperplasia (NIH) in atherosclerosis and restenosis post-balloon angioplasty and stent insertion. Although numerous cytotoxic and cytostatic therapeutics have been developed to reduce NIH, it is improbable that a multifactorial disease can be successfully treated by focusing on a preconceived hypothesis. We, therefore, aimed to identify key molecules involved in NIH via a hypothesis-free approach. We analyzed four datasets (GSE28829, GSE43292, GSE100927, and GSE120521), evaluated differentially expressed genes (DEGs) in wire-injured femoral arteries of mice, and determined their association with VSMC proliferation in vitro. Moreover, we performed RNA sequencing on platelet-derived growth factor (PDGF)-stimulated human VSMCs (hVSMCs) post-phosphoenolpyruvate carboxykinase 2 (PCK2) knockdown and investigated pathways associated with PCK2. Finally, we assessed NIH formation in Pck2 knockout (KO) mice by wire injury and identified PCK2 expression in human femoral artery atheroma. Among six DEGs, only PCK2 and RGS1 showed identical expression patterns between wire-injured femoral arteries of mice and gene expression datasets. PDGF-induced VSMC proliferation was attenuated when hVSMCs were transfected with PCK2 siRNA. RNA sequencing of PCK2 siRNA-treated hVSMCs revealed the involvement of the Akt-FoxO-PCK2 pathway in VSMC proliferation via Akt2, Akt3, FoxO1, and FoxO3. Additionally, NIH was attenuated in the wire-injured femoral artery of Pck2-KO mice and PCK2 was expressed in human femoral atheroma. PCK2 regulates VSMC proliferation in response to vascular injury via the Akt-FoxO-PCK2 pathway. Targeting PCK2, a downstream signaling mediator of VSMC proliferation, may be a novel therapeutic approach to modulate VSMC proliferation in atherosclerosis.

Anti-Mitoticpotential Identification of Nyale (Eunice sp.) in The Tourism Area of Kuta Beach, Lombok Island, West Nusa Tenggara

BACKGROUND: BauNyale festival is a Lombok tradition that originated in the Kuta beach tourism area in Central Lombok. The locals of Lombok Island gathered in this location to harvest marine worms known as Nyale (Eunice sp.). The ability of marine worms to act as anticancer agents has received little attention in Indonesia. AIM: This study aimed to examine the biomolecules compounds of Nyale as antimitotic candidates. METHODS: This was a preliminary study using post-test only with a control group design. The sample of this study was Nyale (Eunice sp.), and sea urchin (Tripneustes ventricosus) collected from Kuta beach, Central Lombok. The Nyale was extracted with 96% ethanol as the solvent. Gas Chromatography-Mass Spectrometry (GCMS) was used to determine the content of bioactive compounds. Sea urchin embryos were divided into four treatment groups (control; 10 mg, 100 mg, and 1000 mg; 1000 mg of Nyale extract). After 2 h of fertilization incubation, the number of cell division phases (2–32 cells) was counted. The data were analyzed using ANOVA. RESULTS: The results of the GCMS test revealed that there were ten different compounds in the Nyale ethanol extract. There was a tendency for cleavage when testing the anti-mitotic potential of Nyale extract in each group. There was a significant difference in the percentage of cell changes in all treatments (control, 10 mg, 100 mg, and 1000 mg) (p < 0.005). CONCLUSION: Bioactive compounds found in marine worms (nyale) influence the percentage of cell division (anti-mitotic) in sea urchin embryos.

Navitoclax Enhances the Therapeutic Effects of PLK1 Targeting on Lung Cancer Cells in 2D and 3D Culture Systems

The efficacy of antimitotics is limited by slippage, whereby treated cells arrested in mitosis exit mitosis without cell division and, eventually, escape apoptosis, constituting a serious resistance mechanism to antimitotics. Strategies to overcome slippage should potentiate the cancer cell killing activity of these antimitotics. Such strategies should accelerate cell death in mitosis before slippage. Here, we undertook a mechanistic analysis to test whether the apoptosis activator Navitoclax potentiates apoptosis triggered by the antimitotic BI2536, a potent inhibitor of Polo-like kinase 1 (PLK1) with the goal of overcoming slippage. We found that cancer cells in 2D cultures treated with BI2536 alone accumulate in mitosis, but a significant fraction of arrested cells undergo slippage and survive. Remarkably, combining BI2536 with Navitoclax dramatically reduces slippage, shifting the cell fate to accelerated death in mitosis. The results are confirmed in 3D spheroids, a preclinical system that mimics in vivo tumor drug responses. Importantly, in 3D spheroids, the effect of the BI2536/Navitoclax combination requires a lower therapeutic dosage of each drug, underlying its potential to improve the therapeutic index. Our results highlight the relevance of apoptosis potentiators to circumvent slippage associated with antimitotics. The combination of BI2536 with Navitoclax shows in vitro synergy/additive effect, which warrants further clinical research.

BP-M345, a New Diarylpentanoid with Promising Antimitotic Activity

Previously, we reported the in vitro growth inhibitory effect of diarylpentanoid BP-M345 on human cancer cells. Nevertheless, at that time, the cellular mechanism through which BP-M345 exerts its growth inhibitory effect remained to be explored. In the present work, we report its mechanism of action on cancer cells. The compound exhibits a potent tumor growth inhibitory activity with high selectivity index. Mechanistically, it induces perturbation of the spindles through microtubule instability. As a consequence, treated cells exhibit irreversible defects in chromosome congression during mitosis, which induce a prolonged spindle assembly checkpoint-dependent mitotic arrest, followed by massive apoptosis, as revealed by live cell imaging. Collectively, the results indicate that the diarylpentanoid BP-M345 exerts its antiproliferative activity by inhibiting mitosis through microtubule perturbation and causing cancer cell death, thereby highlighting its potential as antitumor agent.

Generation of Two Paclitaxel-Resistant High-Grade Serous Carcinoma Cell Lines With Increased Expression of P-Glycoprotein

Debulking surgery followed by chemotherapy are the standard of care for high-grade serous carcinoma. After an initial good response to treatment, the majority of patients relapse with a chemoresistant profile, leading to a poor overall survival. Chemotherapy regimens used in high-grade serous carcinomas are based in a combination of classical chemotherapeutic drugs, namely, Carboplatin and Paclitaxel. The mechanisms underlying drug resistance and new drug discovery are crucial to improve patients’ survival. To uncover the molecular mechanisms of chemoresistance and test drugs capable of overcoming this resistant profile, it is fundamental to use good cellular models capable of mimicking the chemoresistant disease. Herein, we established two high-grade serous carcinoma cell lines with intrinsic resistance to Carboplatin and induced Paclitaxel resistance (OVCAR8 PTX R C and OVCAR8 PTX R P) derived from the OVCAR8 cell line. These two chemoresistant cell line variants acquired an enhanced resistance to Paclitaxel-induced cell death by increasing the drug efflux capacity, and this resistance was stable in long-term culture and following freeze/thaw cycles. The mechanism underlying Paclitaxel resistance resides in a significant increase in P-glycoprotein expression and, when this drug efflux pump was blocked with Verapamil, cells re-acquired Paclitaxel sensitivity. We generated two high-grade serous carcinoma cell lines, with a double-chemoresistant (Carboplatin and Paclitaxel) phenotype that mimics the majority of tumor recurrences in ovarian cancer context. This robust tool is suitable for preliminary drug testing towards the development of therapeutic strategies to overcome chemoresistance.

Do Lipid-based Nanoparticles Hold Promise for Advancing the Clinical Translation of Anticancer Alkaloids?

Since the commercialization of morphine in 1826, numerous alkaloids have been isolated and exploited effectively for the betterment of mankind, including cancer treatment. However, the commercialization of alkaloids as anticancer agents has generally been limited by serious side effects due to their lack of specificity to cancer cells, indiscriminate tissue distribution and toxic formulation excipients. Lipid-based nanoparticles represent the most effective drug delivery system concerning clinical translation owing to their unique, appealing characteristics for drug delivery. To the extent of our knowledge, this is the first review to compile in vitro and in vivo evidence of encapsulating anticancer alkaloids in lipid-based nanoparticles. Alkaloids encapsulated in lipid-based nanoparticles have generally displayed enhanced in vitro cytotoxicity and an improved in vivo efficacy and toxicity profile than free alkaloids in various cancers. Encapsulated alkaloids also demonstrated the ability to overcome multidrug resistance in vitro and in vivo. These findings support the broad application of lipid-based nanoparticles to encapsulate anticancer alkaloids and facilitate their clinical translation. The review then discusses several limitations of the studies analyzed, particularly the discrepancies in reporting the pharmacokinetics, biodistribution and toxicity data. Finally, we conclude with examples of clinically successful encapsulated alkaloids that have received regulatory approval and are undergoing clinical evaluation.

Aurora B Tension Sensing Mechanisms in the Kinetochore Ensure Accurate Chromosome Segregation

The accurate segregation of chromosomes is essential for the survival of organisms and cells. Mistakes can lead to aneuploidy, tumorigenesis and congenital birth defects. The spindle assembly checkpoint ensures that chromosomes properly align on the spindle, with sister chromatids attached to microtubules from opposite poles. Here, we review how tension is used to identify and selectively destabilize incorrect attachments, and thus serves as a trigger of the spindle assembly checkpoint to ensure fidelity in chromosome segregation. Tension is generated on properly attached chromosomes as sister chromatids are pulled in opposing directions but resisted by centromeric cohesin. We discuss the role of the Aurora B kinase in tension-sensing and explore the current models for translating mechanical force into Aurora B-mediated biochemical signals that regulate correction of chromosome attachments to the spindle.

Using Budding Yeast to Identify Molecules That Block Cancer Cell 'Mitotic Slippage' Only in the Presence of Mitotic Poisons

Research on the budding yeast Saccharomyces cerevisiae has yielded fundamental discoveries on highly conserved biological pathways and yeast remains the best-studied eukaryotic cell in the world. Studies on the mitotic cell cycle and the discovery of cell cycle checkpoints in budding yeast has led to a detailed, although incomplete, understanding of eukaryotic cell cycle progression. In multicellular eukaryotic organisms, uncontrolled aberrant cell division is the defining feature of cancer. Some of the most successful classes of anti-cancer chemotherapeutic agents are mitotic poisons. Mitotic poisons are thought to function by inducing a mitotic spindle checkpoint-dependent cell cycle arrest, via the assembly of the highly conserved mitotic checkpoint complex (MCC), leading to apoptosis. Even in the presence of mitotic poisons, some cancer cells continue cell division via 'mitotic slippage', which may correlate with a cancer becoming refractory to mitotic poison chemotherapeutic treatments. In this review, knowledge about budding yeast cell cycle control is explored to suggest novel potential drug targets, namely, specific regions in the highly conserved anaphase-promoting complex/cyclosome (APC/C) subunits Apc1 and/or Apc5, and in a specific N-terminal region in the APC/C co-factor cell division cycle 20 (Cdc20), which may yield molecules which block 'mitotic slippage' only in the presence of mitotic poisons.