Abstract:
The search for novel anti-cancer compounds which can circumvent chemotherapeutic drug
resistance and limit systemic toxicity remains a priority. 2-Ethyl-3-O-sulphamoyl-estra-1,3,5(10)15-
tetraene-3-ol-17one (ESE-15-one) and 2-ethyl-3-O-sulphamoyl-estra-1,3,5(10)16-tetraene (ESE-16) are
sulphamoylated 2-methoxyestradiol (2-ME) analogues designed by our research team. Although
their cytotoxicity has been demonstrated in vitro, the temporal and mechanistic responses of the
initiated intracellular events are yet to be determined. In order to do so, assays investigating the
compounds’ effects on microtubules, cell cycle progression, signalling cascades, autophagy and
apoptosis were conducted using HeLa cervical- and MDA-MB-231 metastatic breast cancer cells.
Both compounds reversibly disrupted microtubule dynamics as an early event by binding to the
microtubule colchicine site, which blocked progression through the cell cycle at the G1/S- and
G2/M transitions. This was supported by increased pRB and p27Kip1 phosphorylation. Induction of
apoptosis with time-dependent signalling involving the p-JNK, Erk1/2 and Akt/mTOR pathways
and loss of mitochondrial membrane potential was demonstrated. Inhibition of autophagy attenuated
the apoptotic response. In conclusion, the 2-ME analogues induced a time-dependent cross-talk
between cell cycle checkpoints, apoptotic signalling and autophagic processes, with an increased
reactive oxygen species formation and perturbated microtubule functioning appearing to connect the
processes. Subtle differences in the responses were observed between the two compounds and the
different cell lines.
