Novel approach to target cancer stem cells for therapy

Anti-cancer activity of pyridoxal phosphate and metformin combination in human pancreatic cancer cells

Background: Pancreatic cancer is the foremost cause of cancer-related deaths in many developed countries with a poor prognosis. With advanced disease conditions chemotherapy, surgery followed by radiation is the regimen to prolong the survival. But a complete cure is questionable. Metformin is the first-line drug used for the treatment of type 2 diabetes in the world. Aim: The study aims to assess the anti-cancer activity of metformin with the combination of micronutrient pyridoxal phosphate (PLP) in the human pancreatic cancer cell line (PANC-1). Methods: Panc1 cells were maintained in vitro cell culture conditions. The IC50 concentrations of metformin and PLP were estimated and selected by using MTT assay. Morphological changes upon treatments were observed under microscope. Distribution of cells pattern was observed with propidium iodide dye in cell cycle assay. Different phases of cell distribution were studied with apoptosis assay. Results: More morphological changes were observed with PLP followed metformin. MTT assay revelled the IC50 concentrations of metformin and PLP were 20.95 ± 0.98 mM and 5.70 ± 0.07 mM. The cell cycle assay revealed that the percentage of cells was arrested in different phases with the treatments. Apoptosis assay revelled metformin increased necrosis population to 9.9%, whereas PLP has enhanced to 14.2% apoptosis. Tumour suppressor protein p53 levels had increased to 24.8% with PLP and 3.5% with metformin. Conclusion: In conclusion, PLP has significantly induced cell cycle arrest, apoptosis and enhanced p53 protein expression but a combination of PLP with metformin drug has not synergised anti-cancer activity in human PANC1 cells.

A Combination Therapy of pHRE-Egr1-HSV-TK/Anti-CD133McAb-131I/MFH Mediated by FePt Nanoparticles for Liver Cancer Stem Cells

It has been evidenced that liver cancer stem cells (LCSCs) are to blame hepatocellular carcinoma (HCC) occurrence, development, metastasis, and recurrence. Using iron-platinum nanoparticles (FePt-NPs) as a carrier and CD133 antigen as a target, a new strategy to targetly kill LCSCs by integrating HSV-TK suicide gene, 131I nuclide irradiation, and magnetic fluid hyperthermia (MFH) together was designed and investigated in the present study. The results showed that FePt-NPs modified with PEI (PEI-FePt-NPs) could bind with DNA, and the best binding ratio was 1 : 40 (mass ratio). Moreover, DNA binding to PEI-FePt-NPs could refrain from Dnase1 enzyme digestion and could release under certain conditions. LCSCs (CD133+ Huh-7 cells) were transfected with pHRE-Egr1-HSV-TK by PEI-FePt-NPs, and the transfection efficiency was 53.65±3.40%. These data showed a good potential of PEI-FePt-NPs as a gene transfer carrier.131I was labeled with anti-CD133McAb in order to facilitate therapy targeting. The combined intervention of pHRE-Egr1-HSV-TK/anti-CD133McAb-131I/MFH mediated by PEI-FePt-NPs could greatly inhibit LCSCs’ growth and induce cell apoptosis in vitro, significantly higher than any of the individual interventions (p<0.05). This study offers a practicable idea for LCSC treatment, and PEI-FePt-NPs may act as novel nonviral gene vectors and a magnetic induction medium.

Spironolactone inhibits the growth of cancer stem cells by impairing DNA damage response

The cancer stem cell (CSC) model suggests that a subpopulation of cells within the tumor, the CSCs, is responsible for cancer relapse and metastasis formation. CSCs hold unique characteristics, such as self-renewal, differentiation abilities, and resistance to chemotherapy, raising the need for discovering drugs that target CSCs. Previously we have found that the antihypertensive drug spironolactone impairs DNA damage response in cancer cells. Here we show that spironolactone, apart from inhibiting cancerous cell growth, is also highly toxic to CSCs. Notably, we demonstrate that CSCs have high basal levels of DNA double-strand breaks (DSBs). Mechanistically, we reveal that spironolactone does not damage the DNA but impairs DSB repair and induces apoptosis in cancer cells and CSCs while sparing healthy cells. In vivo, spironolactone treatment reduced the size and CSC content of tumors. Overall, we suggest spironolactone as an anticancer reagent, toxic to both cancer cells and, particularly to, CSCs.

Systemic mechanisms and effects of ionizing radiation: A new 'old' paradigm of how the bystanders and distant can become the players

Exposure of cells to any form of ionizing radiation (IR) is expected to induce a variety of DNA lesions, including double strand breaks (DSBs), single strand breaks (SSBs) and oxidized bases, as well as loss of bases, i.e., abasic sites. The damaging potential of IR is primarily related to the generation of electrons, which through their interaction with water produce free radicals. In their turn, free radicals attack DNA, proteins and lipids. Damage is induced also through direct deposition of energy. These types of IR interactions with biological materials are collectively called 'targeted effects', since they refer only to the irradiated cells. Earlier and sometimes 'anecdotal' findings were pointing to the possibility of IR actions unrelated to the irradiated cells or area, i.e., a type of systemic response with unknown mechanistic basis. Over the last years, significant experimental evidence has accumulated, showing a variety of radiation effects for 'out-of-field' areas (non-targeted effects-NTE). The NTE involve the release of chemical and biological mediators from the 'in-field' area and thus the communication of the radiation insult via the so called 'danger' signals. The NTE can be separated in two major groups: bystander and distant (systemic). In this review, we have collected a detailed list of proteins implicated in either bystander or systemic effects, including the clinically relevant abscopal phenomenon, using improved text-mining and bioinformatics tools from the literature. We have identified which of these genes belong to the DNA damage response and repair pathway (DDR/R) and made protein-protein interaction (PPi) networks. Our analysis supports that the apoptosis, TLR-like and NOD-like receptor signaling pathways are the main pathways participating in NTE. Based on this analysis, we formulate a biophysical hypothesis for the regulation of NTE, based on DNA damage and apoptosis gradients between the irradiation point and various distances corresponding to bystander (5mm) or distant effects (5cm). Last but not least, in order to provide a more realistic support for our model, we calculate the expected DSB and non-DSB clusters along the central axis of a representative 200.6MeV pencil beam calculated using Monte Carlo DNA damage simulation software (MCDS) based on the actual beam energy-to-depth curves used in therapy.