Binding modes of cabazitaxel with the different human β-tubulin isotypes: DFT and MD studies

Exploring Pyrrolo-Fused Heterocycles as Promising Anticancer Agents: An Integrated Synthetic, Biological, and Computational Approach

Five new series of pyrrolo-fused heterocycles were designed through a scaffold hybridization strategy as analogs of the well-known microtubule inhibitor phenstatin. Compounds were synthesized using the 1,3-dipolar cycloaddition of cycloimmonium N-ylides to ethyl propiolate as a key step. Selected compounds were then evaluated for anticancer activity and ability to inhibit tubulin polymerization in vitro. Notably, pyrrolo[1,2-a]quinoline 10a was active on most tested cell lines, performing better than control phenstatin in several cases, most notably on renal cancer cell line A498 (GI₅₀ 27 nM), while inhibiting tubulin polymerization in vitro. In addition, this compound was predicted to have a promising ADMET profile. The molecular details of the interaction between compound 10a and tubulin were investigated through in silico docking experiments, followed by molecular dynamics simulations and configurational entropy calculations. Of note, we found that some of the initially predicted interactions from docking experiments were not stable during molecular dynamics simulations, but that configurational entropy loss was similar in all three cases. Our results suggest that for compound 10a, docking experiments alone are not sufficient for the adequate description of interaction details in terms of target binding, which makes subsequent scaffold optimization more difficult and ultimately hinders drug design. Taken together, these results could help shape novel potent antiproliferative compounds with pyrrolo-fused heterocyclic cores, especially from an in silico methodological perspective.

Identification of Regulators for Ciliary Disassembly by a Chemical Screen

Cilia are organelles for cellular signaling and motility. They are assembled in G0/G1 and disassembled prior to mitosis. Compared to what is known about ciliary assembly, less is understood about ciliary disassembly. To uncover new mechanisms of ciliary disassembly, we performed an unbiased chemical screen. Chlamydomonas reinhardtii cells were experimentally induced for ciliary disassembly by treatment with sodium pyrophosphate. An FDA approved drug library (HY-L022P-1, MedChemExpress) was used for the screening. Primary screening with further experiments has identified microtubule stabilizer taxanes, CDK4/6 inhibitor abemaciclib and Raf inhibitor dabrafenib being effective in inhibiting ciliary disassembly induced experimentally but also under physiological conditions. In addition, their effects on ciliary disassembly in mammalian cells has also been confirmed. Thus, our studies have not only revealed new mechanisms in ciliary disassembly but also provided new tools for studying ciliary disassembly. These discovered drugs may be used for therapeutic interventions of disorders involving ciliary degeneration such as retinopathies.

Active targeting of orthotopic glioma using biomimetic liposomes co-loaded elemene and cabazitaxel modified by transferritin

BACKGROUND

Effective treatment of glioma requires a nanocarrier that can cross the blood-brain barrier (BBB) to target the tumor lesion. In the current study, elemene (ELE) and cabazitaxel (CTX) liposomes were prepared by conjugating liposomes with transferrin (Tf) and embedding the cell membrane proteins of RG2 glioma cells into liposomes (active-targeting biomimetic liposomes, Tf-ELE/CTX@BLIP), which exhibited effective BBB infiltration to target glioma.

RESULTS

The findings showed that Tf-ELE/CTX@BLIP was highly stable. The liposomes exhibited highly significant homologous targeting and immune evasion in vitro and a 5.83-fold intake rate compared with classical liposome (ELE/CTX@LIP). Bioluminescence imaging showed increased drug accumulation in the brain and increased tumor penetration of Tf-ELE/CTX@BLIP in orthotopic glioma model nude mice. Findings from in vivo studies indicated that the antitumor effect of the Tf-ELE/CTX@BLIP led to increased survival time and decreased tumor volume in mice. The average tumor fluorescence intensity after intravenous administration of Tf-ELE/CTX@BLIP was 65.2, 12.5, 22.1, 6.6, 2.6, 1.5 times less compared with that of the control, CTX solution, ELE solution, ELE/CTX@LIP, ELE/CTX@BLIP, Tf-ELE/CTX@LIP groups, respectively. Histopathological analysis showed that Tf-ELE/CTX@BLIP were less toxic compared with administration of the CTX solution.

CONCLUSION

These findings indicate that the active-targeting biomimetic liposome, Tf-ELE/CTX@BLIP, is a promising nanoplatform for delivery of drugs to gliomas.

Dichotomous role of microtubule associated protein tau as a biomarker of response to and a target for increasing efficacy of taxane treatment in cancers of epithelial origin

Cancer is the second leading cause of death worldwide, and the World Health Organization estimates that one in six deaths globally is due to cancer. Chemotherapy is one of the major modalities used to treat advanced cancers and their metastasis. However, the existence of acquired and intrinsic resistance to anti-cancer drugs often diminishes their therapeutic effect. In order to pre-select patients who could benefit the most from these treatments, the efforts of many research groups have been focused on identification of biomarkers of therapy response. Taxanes paclitaxel (Taxol) and docetaxel (Taxotere) have been introduced as chemotherapy for treatment of cancers of ovary in 1992 and breast in 1996, respectively. Since then, clinical use of taxanes has expanded to include lung, prostate, gastric, head and neck, esophageal, pancreatic, and cervical cancers, as well as Kaposi sarcoma. Several independent molecular mechanisms have been shown to support taxane chemoresistance. One such mechanism is dependent on microtubule associated protein tau. Tau binds to the same site on the inner side of the microtubules that is also occupied by paclitaxel or docetaxel, and several studies have demonstrated that low/no tau expression significantly correlated with better response to the taxane treatment, suggesting that levels of tau expression could have a predictive value in pre-selecting patient cohorts that are likely to benefit from the treatment. However, several other studies have found no correlation between tau expression and taxane response, introducing a controversy and precluding its wide use as a predictive biomarker. Based on the knowledge of tau biology accumulated thus far, in this review we attempt to critically analyze the studies that evaluated tau as a biomarker of taxane response. Further, we identify yet unknown aspects of tau biology understanding of which is necessary for improvement of development of tau as a biomarker of response and a target for increasing response to taxane treatment.

Conformers, Properties of the Anticancer Drug Plocabulin, and its Binding Mechanism with p-Glycoprotein: DFT and MD Studies

Plocabulin (PM060184) is a promising new anticancer drug as a microtubule inhibitor. The conformational structure and properties of plocabulin have been studied theoretically. The initial structure was screened by the B3LYP/3-21G* method, and then 32 unique conformations were further optimised with the B3LYP/6-311G* method. The single-point energies were determined at the M06-L/6-311G(2df,p) level. The UV excitation of the most stable plocabulin conformation in methanol was studied by the TD-CAM-B3LYP/6-311G(2df,p) method. High-quality human p-glycoprotein model was obtained through homology modelling. The binding interaction between p-glycoprotein and plocabulin was studied by docking and MD simulation. LEU65, TYR310, ILE340, THR945, PHE983, MET986, and GLN990 were found to be important amino acid residues in the interaction. From a certain perspective, the ‘reverse exclusion’ mechanism of plocabulin with p-glycoprotein was illustrated, and this mechanism provides theoretical guidance for the structural modification of plocabulin and for design of drug’s to avoid p-glycoprotein-mediated drug resistance.

Mechanisms of Taxane Resistance

The taxane family of chemotherapy drugs has been used to treat a variety of mostly epithelial-derived tumors and remain the first-line treatment for some cancers. Despite the improved survival time and reduction of tumor size observed in some patients, many have no response to the drugs or develop resistance over time. Taxane resistance is multi-faceted and involves multiple pathways in proliferation, apoptosis, metabolism, and the transport of foreign substances. In this review, we dive deeper into hypothesized resistance mechanisms from research during the last decade, with a focus on the cancer types that use taxanes as first-line treatment but frequently develop resistance to them. Furthermore, we will discuss current clinical inhibitors and those yet to be approved that target key pathways or proteins and aim to reverse resistance in combination with taxanes or individually. Lastly, we will highlight taxane response biomarkers, specific genes with monitored expression and correlated with response to taxanes, mentioning those currently being used and those that should be adopted. The future directions of taxanes involve more personalized approaches to treatment by tailoring drug-inhibitor combinations or alternatives depending on levels of resistance biomarkers. We hope that this review will identify gaps in knowledge surrounding taxane resistance that future research or clinical trials can overcome.