Synthesis and Preclinical Evaluation of Indole Triazole Conjugates as Microtubule Targeting Agents that are Effective against MCF-7 Breast Cancer Cell Lines
Authors: Yele Vidyasrilekha , Pindiprolu Sai Kiran S.S. , Sana Sravani , Ramamurty D.S.V.N.M. , Madasi Jayanthi R.K. , Vadlamani Swapna 
Published: September 2020

Background:

Microtubules are considered to be an important therapeutic target for most of the anticancer
drugs. These are highly dynamic structures comprising of α-tubulin and β-tubulin which are usually
heterodimers and found to be involved in cell movement, intracellular trafficking, and mitosis inhibition of
which might kill the tumour cells or inhibit the abnormal proliferation of cells. Most of the tubulin polymerization
inhibitors, such as Vinca alkaloids, consist of Indole as the main scaffold. The literature also suggests using
triazole moiety in the chemical entities, potentiating the inhibitory activity against cell proliferation. So, in our
study, we used indole triazole scaffolds to synthesize the derivatives against tubulin polymerization.

Objective:

The main objective of this study to synthesize indole triazole conjugates by using environmentally
friendly solvents (green chemistry) and click chemistry. To carry out the MTT assay and tubulin polymerization
assay for the synthesized indole triazole conjugates.

Methods:

All the synthesized molecules were subjected to molecular docking studies using Schrodinger suite
and the structural confirmation was performed by Mass, proton-NMR and carbon-NMR, documented in DMSO
and CDCL3. Biological studies were performed using DU145 (prostate cancer), A-549 (lung cancer) and, MCF-7
(breast cancer), cell lines obtained from ATCC were maintained as a continuous culture. MTT assay was performed
for the analogues using standard protocol. Cell cycle analysis was carried out using flow cytometry.

Results:

The Indole triazole scaffolds were synthesized using the principles of Green chemistry. The triazole
formation is mainly achieved by using the Click chemistry approach. Structural elucidation of synthesized compounds
was performed using Mass spectroscopy (HR-MS), Proton-Nuclear Magnetic Spectroscopy (1H-NMR)
and Carbon-Nuclear Magnetic Spectroscopy (13C-NMR). The XP-docked poses and free energy binding calculations
revealed that 2c and 2g molecules exhibited the highest docking affinity against the tubulin-colchicine
domain (PDB:1SA0). In vitro cytotoxic assessment revealed that 2c and 2g displayed promising cytotoxicity in
MTT assay (with CTC50 values 3.52μM and 2.37μM) which are in good agreement with the computational
results. 2c and 2g also arrested 63 and 66% of cells in the G2/M phase, respectively, in comparison to control
cells (10%) and tubulin polymerization inhibition assay revealed that 2c and 2g exhibited significant inhibition
of tubulin polymerization with IC50 values of 2.31μM, and 2.62μM, respectively in comparison to Nocodazole, a
positive control, resulted in an IC50 value of 2.51μM.

Conclusion:

Indole triazole hybrids were synthesized using click chemistry, and docking studies were carried
out using Schrodinger for the designed molecules. Process Optimization has been done for both the schemes.
Twelve compounds (2a-2l) have been successfully synthesized and analytical evaluation was performed using
NMR and HR-MS. In vitro evaluation was for the synthesized molecules to check tubulin polymerization inhibition
for antiproliferative action. Among the synthesized compounds, 2c and 2g have potent anticancer activities
by inhibiting tubulin polymerization.