Targeting colon cancer stem cells using novel doublecortin like kinase 1 antibody functionalized folic acid conjugated hesperetin encapsulated chitosan nanoparticles

The cancer stem cell (CSC) hypothesis is an evolving oncogenesis concept. CSCs have a distinct ability to self-renew themselves and also give rise to a phenotypically diverse population of cells. Targeting CSCs represents a promising strategy for cancer treatment. Plant-derived compounds are potent in restricting the expansion of CSCs. DCLK1 has been already reported as a colon CSC specific marker. Nanoparticles can effectively inhibit multiple types of CSCs by targeting specific markers. We have synthesized DCLK1 functionalized folic acid conjugated hesperetin encapsulated chitosan nanoparticles (CFH-DCLK1), specifically to target CSCs. In this regard, we have performed proliferation assay, colony formation assay, cell migration assay, apoptosis assay, flow cytometry analysis, real-time RT- PCR and western blot analyses to determine the effect of CFH-DCLK1 and CFH nanoparticles in HCT116-colon cancer cells. In our study, we have determined the median inhibitory concentration (IC50) of CFH (47.8 µM) and CFH-DCLK1 (4.8 µM) nanoparticles in colon cancer cells. CFH-DCLK1 nanoparticles induced apoptosis and inhibited the migration and invasion of colon cancer cells. Real time PCR and western blot results have demonstrated that the treatment with CFH-DCLK1 nanoparticles significantly reduced the expression of CSC markers such as DCLK1, STAT1 and NOTCH1 compared to the CFH alone in HCT116 colon cancer cells. Finally, in the 3D spheroid model, CFH-DCLK1 nanoparticles significantly inhibited the colonosphere growth. Overall, our results highlight the effectiveness of CFH-DCLK1 nanoparticles in targeting the colon cancer cells and CSCs. This study would lead to the development of therapies targeting both cancer cells and CSCs simultaneously using nanoformulated drugs, which could bring changes in the current cancer treatment strategies.

RNA binding protein PUM1 promotes colon cancer cell proliferation and migration

Colon cancer is the third leading cause of death worldwide and sixth in India, where it is the cause of 5.8% of the total deaths. Pumilio-1 (PUM1) is an RNA binding protein whose regulatory role is by binding to the consensus 5'UGUANAUA3' sequence on the 3'UTR of the mRNA targets and post-transcriptionally repressing their expression. This study is the first of its kind to report the expression or function of PUM1 in colon cancer. We found that PUM1 mRNA expression is high in primary and metastatic colon cancer cell lines when compared to the normal colon cell line. Immunohistochemistry analysis showed similar trend wherein compared to the normal colon tissue, PUM1 was found to be overexpressed in both adenocarcinoma and in metastatic carcinoma. This confirms the role of PUM1 in colon cancer progression. PUM1 overexpression study in HCT116 revealed that cells transfected with PUM1 plasmid show an increased rate of proliferation, migration and colony formation. Overexpressing PUM1 increases the number and size of spheroids indicating the role of PUM1 in maintaining cancer stem cells. Overall, this is the first study that has shown the role of PUM1 in colon cancer development.

Chitosan-based nano-formulation enhances the anticancer efficacy of hesperetin

Cancer is one of the major causes of increased morbidity and mortality in modern society. Colorectal cancer is the third leading cause for cancer related death worldwide. Current chemotherapeutics are not very effective and have severe side effects. Hesperetin is a bioflavonoid from citrus fruits and its clinical use is restricted because of the poor water solubility. Folate receptor is overexpressed in various cancer cells. Therefore, we synthesized the chitosan folate hesperetin nanoparticle (CFH) by covalently conjugating folic acid with chitosan molecules. The size of the CFH nanoparticles is around 450nm, which is advantageous for passively targeting the cancer cell specifically due to the leaky vasculature of the tumour. Particle surface and size were observed using SEM and TEM studies. The results show that hesperetin has an IC50 value of 190μM and it induces apoptosis in HCT15 cells, however, CFH is very potent in inhibiting the proliferation with the IC50 value of 28μM. In addition, CFH inhibited colony formation and induced apoptosis by regulating the expression of proapoptotic genes expression. Therefore, the chitosan - folic acid conjugation appears to be the suitable carrier for colorectal cancer cell-specific delivery of hesperetin.