THERAPEUTIC TARGETING OF CDK4 KINASE IN PANCREATIC CANCER WITH SINGLE-WALLED CARBON NANOTUBES

Luc CHAVIGNON

This thesis explores the chemical, optical, and electronic properties of single-walled carbon nanotubes (SWNT) as carriers for drug delivery . Two drugs were studied: (1) Doxorubicin (DOX), an anthracycline that is well documented in the literature, characterized byintense absorption and fluorescence spectroscopic signals, used as a model drug to investigate adsorption on SWNTs through a multi-spectroscopic approach and (2) Abemaciclib (Ab), an ATP-competitive inhibitor of CDK4 and CDK6 kinases that is hyperactivated in pancreatic cancer, which was characterized in complementary spectroscopic, biochemical and biological tests. SWNT were first dispersed in carboxymethylcellulose (CMC), a biocompatible polyelectrolyte used as a dispersing and stabilizing agent for SWNT. Drugs were then adsorbed onto their surface to form SWNT/CMC/DOX and SWNT/CMC/Ab complexes. Adsorption and subsequent desorption of drugs at different temperatures were monitored and verified by studying the FL signal of SWNT in the near IR using Raman/FL spectroscopy. These were then complemented by UV-vis-NIR absorption and fluorescence spectroscopy studies for Doxorubicin, and kinase activity tests for Abemaciclib. The potential of SWNT/CMC/Ab complexes to inhibit proliferation of pancreatic cancer cell cultures (PANC1) was determined in comparison with Abemaciclib in solution and SWNT/CMC complexes. Typical structures of SWNT/CMC/drug complexes can be imagined from our spectroscopic studies performed at different drug concentrations. Several models of Doxorubicin organization on SWNT/CMC can be imagined accounting for the ability of Doxorubicin to self-associate: sub-monolayer, monolayer, and multilayer. A model accounting for adsorption of several layers of Doxorubicin reveals that approximately 90% of Doxorubicin can be loaded onto SWNT complexes, heating these complexes at 60°C promotes release of approximately 20% adsorbed Doxorubicin, a process that is reversible when the temperature returns to 20°C. For SWNT/CMC/Ab complexes, as Abemaciclib does not self-associate, we imagine a structure in which it preferentially adsorbs onto the surface of SWNTs to form a homogeneous monolayer, implying a lower ratio of adsorbed Abemaciclib than Doxorubicin, between 40 and 80%. Spectroscopic studies following heating of SWNT/CMC/Ab complexes at 60°C tend to show reversible temperature desorption similar to that of SWNT/CMC/DOX complexes, kinase activity tests did not confirm any release of Abemaciclib for CDK4 inhibition. Proliferation tests with SWNT/CMC/Ab complexes showed that the complexes have no greater inhibitory potential than Abemaciclib in solution.