9‐Ethynyl noscapine induces G2 /M arrest and apoptosis by disrupting tubulin polymerization in cervical cancer

Abstract

Noscapine is a phthalide isoquinoline alkaloid present in the latex of Papaver somniferum and has demonstrated potent antitumor activity in various cancer models. Structural changes in the core molecule of noscapine architecture have produced a number of potent analogs. We have recently synthesized the novel noscapine analogs (3, 4, and 5) with different functional groups appended at ninth position of natural noscapine. The anticancer activity of these compounds has been investigated using various human cancer cell lines such as HeLa (cervical cancer), DU‐145 (prostate cancer), MCF‐7 (breast cancer), and IMR‐32 (neuroblastoma). One of the compounds in this series, 9‐ethynyl noscapine (5), has demonstrated good anticancer activity against HeLa cells. Biological studies demonstrated that compound 5 decreased cell viability and colony formation in HeLa cells in a concentration dependent manner. To further uncover the mechanism in detail, we evaluated compound 5 effect on cell cycle progression, microtubule dynamics, and apoptosis. Cell cycle and western blotting analysis revealed that 9‐ethynyl noscapine treatment resulted in cell cycle arrest at G2/M and decreased CDK1 and cyclinB1 protein expression. We also observed that 9‐ethynyl noscapine (5) treatment leads to disruption in tubulin polymerization and induction of apoptosis by decreasing expression of bcl2, pro‐caspase 3, and activation of cytochrome C. Taken together, our results indicate that 9‐ethynyl noscapine (5) effectively supresses the growth of cervical cancer cells (HeLa) by disrupting tubulin polymerization, cell cycle progression leading to apoptosis.

An Overview of Natural and Synthetic Phthalides Involved in Cancer Studies: Past, Present, and Future

“…Regarding the mechanism of antitumor action, the antimicrotubule agents have gained considerable attraction as an emerging class of compounds for cancer treatment owing to their improved patient compliance and minimal side effects. [132,165,169,201] Among these, tubulin-binding drugs have been proposed for treatment of various types of treat malignancies [36,40,177] e. g., leukemia, [174,200] ovarian cancer, [166,167] and T-cell lymphoma, [130,167] breast cancer, [148,175,176,202,203] cervical, [132] gastric, [170] and colon cancer, [127,166,204] pancreatic cancer, [166,168] liver, [36,126] lung cancer, [169,171,175] and gliablastoma. [37,166,172] Currently proposed mechanism for the activity of microtubule-targeting drugs in use is based on either promoting excessive stability of microtubules, like the taxane family (e. g., Paclitaxel and Docetaxel) or inducing depolymerization of microtubules such as the vinca alkaloids (e. g., vinblastine, vinorelbine, and vincristine).…”

“…[37,166,172] Currently proposed mechanism for the activity of microtubule-targeting drugs in use is based on either promoting excessive stability of microtubules, like the taxane family (e. g., Paclitaxel and Docetaxel) or inducing depolymerization of microtubules such as the vinca alkaloids (e. g., vinblastine, vinorelbine, and vincristine). [37,132,161,165,173] On the other hand, the mechanism of action of phthalide analogs as a stabilizer or destabilizer microtubules has not been clearly determined and understood, [161,173,199] and the studies to gain more insights onto the anticancer mechanisms of phthalideinduced angiogenesis and apoptosis are still in progress. [173] Despite that, it has been revealed by the ongoing studies that the phthalide analogs only affect the microtubule dynamics [170,173,175,201,204] rather than altering the steady-state monomer polymer equilibrium of microtubule assembly in cells.…”

“…[36,37,40,126,127,130,132,148,161,[165][166][167][169][170][171][172][174][175][176][177] Anticancer properties of noscapine through microtubule dynamics [170,173,175] are based on the binding ability of noscapine to tubulin which is a heterodimeric guanine nucleotide-binding protein. [132,161] It alters the tubulin conformation leading to the formation of a dynamic cytoskeletal filament called microtubules so that cell cycle progression at mitosis has been diminished. [37,165,174,204] In contrast to other microtubule-interacting agents such as Paclitaxel, Noscapine (2) modifies microtubule dynamics without changing the net equilibrium between the monomer and the polymer distribution of tubulin within the cell and without affecting total tubulin polymer mass.…”

“…Regarding the mechanism of antitumor action, the antimicrotubule agents have gained considerable attraction as an emerging class of compounds for cancer treatment owing to their improved patient compliance and minimal side effects [132,165,169,201] . Among these, tubulin‐binding drugs have been proposed for treatment of various types of treat malignancies [36,40,177] e. g., leukemia, [174,200] ovarian cancer, [166,167] and T‐cell lymphoma, [130,167] breast cancer, [148,175,176,202,203] cervical, [132] gastric, [170] and colon cancer, [127,166,204] pancreatic cancer, [166,168] liver, [36,126] lung cancer, [169,171,175] and gliablastoma [37,166,172] .…”

“…Despite that, it has been revealed by the ongoing studies that the phthalide analogs only affect the microtubule dynamics [170,173,175,201,204] rather than altering the steady‐state monomer polymer equilibrium of microtubule assembly in cells [37,165,176] . In other words, such drugs do not change the ratio of tubulin monomer to polymer, hence circular and neuronal toxicity is avoided [132,173] . This superior feature in comparison to the other anti‐microtubule drugs which polymerize microtubules and break down polymers into monomers let these drug candidates highly beneficial for cancer treatment with little or no effect on organs and blood parameters with low toxicity [132] .…”