Hypoxia in Breast Cancer-Scientific Translation to Therapeutic and Diagnostic Clinical Applications

Breast cancer has been the leading cause of female cancer deaths for decades. Intratumoral hypoxia, mainly caused by structural and functional abnormalities in microvasculature, is often associated with a more aggressive phenotype, increased risk of metastasis and resistance to anti-malignancy treatments. The response of cancer cells to hypoxia is ascribed to hypoxia-inducible factors (HIFs) that activate the transcription of a large battery of genes encoding proteins promoting primary tumor vascularization and growth, stromal cell recruitment, extracellular matrix remodeling, cell motility, local tissue invasion, metastasis, and maintenance of the cancer stem cell properties. In this review, we summarized the role of hypoxia specifically in breast cancer, discuss the prognostic and predictive value of hypoxia factors, potential links of hypoxia and endocrine resistance, cancer hypoxia measurements, further involved mechanisms, clinical application of hypoxia-related treatments and open questions.

Cancer stemness contributes to cluster formation of colon cancer cells and high metastatic potentials

The ability of cancer cells to form clusters is a characteristic feature in the development of metastatic tumours with drug resistance. Several studies demonstrated that clusters of circulating tumour cells (CTCs) have a greater metastatic potential to establish new tumours at secondary sites than single CTCs. However, the mechanism of cluster formation is not well understood. In this study, we investigated whether cancer stemness would contribute to cluster formation. We used a tumour sphere culture method to enrich cancer stem cells (CSCs) from colon cancer cells and found that during the second generation of sphere culture, clusters (between 3 and 5 cells) formed within the first 24 hours, whereas the rest remained as single cells. The clusters were analysed for stemness and metastatic potential, including gene expressions for cancer stemness (CD133 and Lgr5), epithelial-mesenchymal transition (E-cadherin and TGF-β 1-3) and hypoxia-induced factors (HIF-1α and HIF-2α). The results showed that the clusters expressed higher levels of these genes and colon CSC surface markers (including CD24, CD44 and CD133) than the single cells. Among these markers, CD24 seemed the major contributor linking the cells into the clusters. These clusters also showed a stronger ability to both form colonies and migrate. Our data collectively suggest that colon cancer stemness contributes to cluster formation and that clustered cells exhibit a great metastatic potential. Our study thus provides a method to study the CTC clusters and derive insight into oncogenesis and metastasis.

Nanodelivery of doxorubicin for age-related macular degeneration

OBJECTIVE

Polymeric nanoparticles (NPs) containing doxorubicin (DOX) were prepared for the inhibition of hypoxia-induced factor 1α (HIF-1α).

SIGNIFICANCE

HIF-1α is responsible for the upregulation of several angiogenic factors, including vascular endothelial growth factor (VEGF). DOX inhibits HIF-1α but is highly toxic. By encapsulating DOX in NPs, drug delivery will be sustained and toxicity will be reduced without limiting efficacy.

METHODS

DOX NPs were prepared using both polylactic coglycolic acid (PLGA) and chitosan. PLGA NPs were prepared via nanoprecipitation (NPC) and single and double emulsion diffusion (SE; DE). Chitosan NPs were formulated using ionic gelation (IG), and complex coacervation (CC). Size, polydispersity index (PDI), and zeta potential (ZP) were determined via dynamic light scattering (DLS) (n = 3). The encapsulation efficiency (EE), drug loading capacity (DLC) (n = 3) and in vitro drug release profiles (IVR) at 37 °C (n = 4) were analyzed via spectroscopy at 480 nm (λ_max). The cytotoxicity of each formulation as well as free DOX solution in ARPE-19 cells was determined via MTT assay after 24 h (n = 3). HIF-1α and VEGF inhibition in ARPE-19 cells were measured via ELISA (n = 3).

RESULTS

The results were consistent with the hypothesis; the NP formulations decreased HIF-1α and VEGF-A expression in ARPE-19 cells with reduced cytotoxicity. SE, DE, and CC demonstrated low ZP as well as the most rapid drug release of the tested formulations. FTIR confirmed the presence of DOX on the SE NP surface, indicating instability.

CONCLUSIONS

SE, DE, and CC destabilized. NPC was the most efficient formulation for the nanodelivery of DOX for AMD.