Benzothiazolo-quinazoline Congeners Function as Anti-microtubule Agents Triggering Mitotic Arrest in Cancer Cells

Background

Antimicrotubule agents effectively block cancer spread and are routinely employed as front-line chemotherapeutics. But patients, who receive Paclitaxel, suffer from peripheral neuropathy, which not only lowers quality of life but also can lead to treatment termination. Therefore, it is essential to identify novel microtubule inhibitors that can act as future front-line chemotherapeutics. In our previous study, we synthesized a cohort of 23 benzothiazolo[3,2-a] quinazoline derivatives employing a tandem copper catalyzed regioselective N-Arylation and aza-michael additions. However, the bioactive potential of the benzothiazolo-quinazoline derivatives are unknown. The synthesized benzothiazolo-quinazoline derivatives structurally resemble the microtubule inhibitors colchicine and CA-4. Therefore in this study; we asked whether benzothiazolo-quinazoline congeners act as microtubule inhibitors.

Materials and Methods

To answer the question, we treated benzothiazolo-quinazoline congeners in a panel of four cancer cell lines and elucidated the molecular mechanism of action of the hit compounds in vitro and in vivo.

Results

We found that benzothiazolo-quinazoline derivatives: 1-3, 6, 10, and 21-23 exhibited superior inhibitory effects with IC5₀ values ranging from 4.2-12.1 μM in HeLa cells. We observed that 1-3, 6, 10, and 21-23 arrest cells in G2/M phase and disrupt microtubule network. In addition, we found that the selected congeners increase transcript and protein levels of mitotic markers. As part of mechanism, we observed that the congeners 1-3, 6, 10, and 21-23 promote tubulin depolymerisation similar to nocodazole, a microtubule depolymerising agent. Further, molecular modelling studies have shown that the congeners occupy the colchicines binding pocket in microtubule. We observed that the congeners 1-3, 6, 10, and 21-23 disrupt blood vessel formation in chick eggs and arrest Zebrafish embryo development.

Conclusion

We conclude that the congeners 1-3, 6, 10, and 21-23 function as antimicrotubule agents. Based on observations, we suggest that the congeners can be lead-optimized to generate next generation of frontline chemotherapeutics.