1661P - Evaluation of photodynamic treatment effects on cancer stem cells in vitro

Date 28 September 2014
Event ESMO 2014
Session Poster Display session
Topics Basic Science
Presenter Elena Selivanova
Citation Annals of Oncology (2014) 25 (suppl_4): iv564-iv573. 10.1093/annonc/mdu359
Authors E.I. Selivanova, S. Makarenko, O. Matchuk, A. Mihailovskaya, I. Zamulaeva
  • Ministry Of Health Of The Russian Federation, FEDERAL STATE INSTITUTION “MEDICAL RADIOLOGICAL RESEARCH CENTER” (MRRC), 249036 - Obninsk/RU

Abstract

Aim

Cancer stem cells (CSC), detected in variety of malignant tumors and cancer cell lines are supposed to determine long-term effect of cancer therapy. CSC have been shown to be more resistant to the low-LET radiation and to a number of anticancer agents in comparison to the other cancer cells. However effects of photodynamic treatment (PT) on CSC have been poorly studied. The aim of this work was to compare accumulation of the photosensitizer (PS) in CSC and non CSC as well as death of these cell populations after PT in vitro.

Methods

CSC were identified by flow cytometry as the side population (SP) of Hoescht33342-excluding cells in melanoma B16 and breast cancer MCF-7 cell cultures. Accumulation of PS “Photolon” (RYP, Belarus) in SP and nonSP cells was studied by flow cytometry for a total period of 2h. In the study of cell death, SP and non-SP cells were sorted, incubated with PS for 1h and exposed to laser light at 661 nm (0.06 W) for 30-60 seconds. Cellular death was assessed with propidium iodide staining 30 min after the irradiation.

Results

In a wide range of PS concentrations (0.7-15.0 mg/ml) a direct linear correlation was observed between the intracellular content of the drug and its concentration in the medium for SP and non-SP cells of both cell lines (r>0.93;p<0.01).The temporal dynamics of PS accumulation was nonlinear and differed in SP and non-SP cells. SP cells accumulated PS significantly weaker than the other cells (1.8-fold for both lines 1h after the addition of the drug, p<0.05) that indicates the ability of SP to actively exclude this compound. However the levels of postradiation death of the SP and non-SP cells did not differ upon various experimental conditions.

Conclusions

These results for the first time experimentally justify the high effectiveness of PT toward CSC elimination. This work was supported by grant of Russian Foundation of Basic Research # 13-04-01721.

Disclosure

All authors have declared no conflicts of interest.