Cytodestructive Effects of Photodynamic Exposure in Primary Cultures of Malignant Glioma Cells

Abstract

Background. Photodynamic therapy (PDT) is a promising adjuvant method for the treatment of malignant gliomas (MG), including tumors with continued growth and tumor recurrences. For the clinical application of PDT, it is important to substantiate the effectiveness of the cytodestructive effect of the combined use of laser irradiation (LI) and photosensitizer (PS). Objective. To evaluate the cytodestructive effects of photodynamic exposure with the use of PS chlorine E6 on primary MG cell cultures. Methods. Primary cell cultures were obtained from samples of biopsy material from patients (n = 6) with a veri­fied diagnosis: 3 primary tumors (1 case of diffuse astrocytoma, NOS (G3), 1 – glioblastoma (GB), NOS (G4), 1 – gliosarcoma (G4)) and 3 – with continued tumor growth (1 – diffuse astrocytoma, NOS (G3), 1 – oligo­dendroglioma, NOS (G3) and 1 – GB, NOS (G4). Groups of cell cultures included: 1) control – cultured in a standard nutrient medium and experimental; 2) cultured with the addition of chlorine E6 (2.0 mg/ml); 3) cultivated without the addition of PS and subjected to LI; 4) cultivated with the addition of chlorine E6 and subsequent exposure to LI. After 24 h, morphological and morpho­metric studies were carried out. Results. The primary MG cultures were characterized by different growth dynamics; mitotic activity of tumor cells varied from the highest rate in the culture of primary GB to lower values – in cultures of recurrent GB and primary astrocytoma and gliosarcoma, and the lowest – in cultures of continued growth of astrocytoma and oligodendroglioma after combined treatment. Direct exposure to chlorine E6 and LI reduced the total number of cells in the culture and their mitotic activity. The greatest cytodestructive effect was achieved with the combined effect of chlorine E6 and LI: the effective dose in the case of primary astrocytoma cells is 10 J/cm2 in pulse mode; for cells of primary GB and gliosarcoma, recurrent astrocytoma and oligodendro­glioma, the effective dose is 25 J/cm2 in pulsed mode. In the case of GB cells, continued growth, a dose of 25 J/cm2 is effective for both continuous and pulsed modes of LI. Conclusions. Primary cell cultures of MG obtained directly from tumor tissue are an adequate model for evaluating the effectiveness of the cytodestructive effect of the combined use of LI and PS for PDT.

Keywords

• malignant glioma
• continued growth
• primary cultures
• photodynamic therapy
• chlorine E6
• laser irradiation