Two of the main limitations of conventional cancer drugs are their lack of ability to discriminate between cancer and normal cells, producing the well-known side effects, and the resistance to radio- and chemotherapy. The resistance is mainly due to the presence of hypoxic (low oxygen) regions in tumours where the Hypoxia Inducible Factor (HIF) transcriptional system regulates the expression of hypoxia-dependent pro-survival and drug resistance genes. The development of a delivery system capable of specifically targeting and penetrating tumours is a promising strategy to overcome these issues. Currently, one of the most investigated agents for cancer targeting is hyaluronic acid (HA), since its main receptor, CD44, is overexpressed in many cancers. However, it is still unclear which cell-related factors influence HA binding and internalisation (collectively called âuptakeâ) into CD44 expressing cells. To address this, the expression of CD44 (standard and variants isoforms, CD44s and CD44v respectively) was evaluated in human dermal fibroblasts (HDF) as healthy control and in a large panel of cancer cell lines. It was found that the expression of CD44v can negatively influence the uptake of HA but, interestingly, the healthy control HDF that expressed high levels of CD44s were less efficient in taking up HA when compared to high expressing CD44s cancer cells. Starting from this knowledge, HA-coated chitosan (CS)-based nanoparticles (NPs), engineered to contain siRNAs to knockdown HIF-1, were used to target CD44s expressing pancreatic cancer cell lines (MIA PaCa-2 and PANC-1). Two different NPs were formulated using low or high molecular weight (LMW or HMW) CS evaluating differences in their internalisation by cells and correlating that with gene silencing studies. Cells showed a slower internalisation of HMW CS/HA NPs compared to the LMW counterpart. However, the latter were slightly more efficient in HIF-1Î± and its downstream target genes knockdown. LMW CS/HA NPs were able to penetrate deeply into multicellular spheroids, but when injected intravenously in tumour bearing mice they resulted not completely stable (with potential decomplexation) as 48 hours post-injection most of HA was detected in the liver and the siRNA in the kidneys. In conclusion, these results provide some understanding on the interplay between CD44 expression, its functionality and the underlying mechanism(s) for HA uptake and importantly, demonstrate that factors other than the amount of CD44 receptor can play a role in the interaction with HA. However, other methods for preparation or in vivo administration of HA/CS NPs need to be evaluated to assess the system stability in a route different from intravenous.
|Date of Award||1 Aug 2019|
- The University of Manchester
|Supervisor||Ian Stratford (Supervisor), Kaye Williams (Supervisor) & Roben Gieling (Supervisor)|