Evaluation of the effect of low and intermediate frequency electromagnetic waves on radiosensitivity

Chinhengo, Angela (2016-12)

Thesis (MSc)--Stellenbosch University, 2016.

Thesis

ENGLISH SUMMARY : The incidence of epidemic Kaposi’s sarcoma in HIV/AIDS patients is high due to their compromised immune system. HIV-positive individuals presenting with cancer tend to be more sensitive to ionizing radiation and are at a higher risk of developing severe side effects during radiotherapy, and there is a need to develop non-invasive methods to preferentially sensitize cancer cells and reduce therapeutic doses. Here, the effects of 100 and 1000 Hz electromagnetic fields (EMF) broadcast via an argon plasma ray tube at 50 W on the radio sensitivity of apparently normal Chinese hamster lung fibroblasts (V79) and human malignant melanoma cells (MeWo) were evaluated using the colony forming assay. Pre-exposure of the fibroblasts to both fields had no effect on their radio sensitivity, if X-ray irradiation followed within 2 h or at 6 h. Significant radio sensitization was observed when X-rays were administered 4 h after EMF exposure. For the MeWo cells, pre-exposure to 100 Hz resulted in a significant radioprotection when irradiation followed within 6 h. However, treatment of these cells with a 1000 Hz field significantly potentiated the effect of X-rays. When cells were irradiated prior to EMF exposure, the V79 cells were marginally protected by the 100 Hz field and sensitized by the 1000 Hz field. In contrast, the melanoma cells were slightly protected by the 1000 Hz field and sensitized by the 100 Hz field. The survival rate of the normal fibroblasts when treated with 2 Gy, in two fractions of 1 Gy 6 h apart, was similar to those obtained when cells received an acute dose of 2 Gy 6 h prior to or after exposure to both EMF frequencies. On the other hand, the melanoma cells were significantly sensitized when they were either treated with a combination of X-rays and then 100 Hz EMF 6 h later or with a combination of either of the EMF frequencies and then X-rays 6 h later. These data suggest that use of electromagnetic fields may sensitize tumours to radiation therapy and reduce normal tissue toxicity. Informed and well-designed combinations of low-medium frequency electromagnetic fields and radiation therapy might be beneficial in the management of cancers, especially epidemic Kaposi’s sarcoma.

AFRIKAANSE OPSOMMING : Die insidensie van epidemiese Kaposi-sarkoom in pasiente met MIV/VIGS is hoog weens die gekompromitteerde immuunstelsel. MIV-positiewe persone met kanker neig om meer gevoelig te wees vir ioniserende bestraling en loop die hoer risiko om ernstige nuwe-effekte op te doen gedurende bestraling. Daar is dus ‘n behoefte om nie-indringende metodes te ontwikkel wat kankerselle by voorkeur meer kwesbaar maak en daardeur terapeutiese bestralingsdosisse te kan verminder. Die navorsing illustreer die gevolge van blootstelling aan 100Hz en 1000Hz elektromagnetiese velde (EMV), geproduseer deur ‘n argon-plasmastraalbuis van 50W, op die radiosensitiwiteit van skynbaar normale long-fibroblaste (V79) van Chinese hamsters en mens melanoomselle (MeWo), gemeet deur gebruik te maak van kolonievormende toetse. Fibroblaste, vooraf blootgestel aan 100Hz en 1000Hz elektromagnetiese velde, het geen uitwerking teen bestraling getoon indien die bestraling binne 2 en 6 uur plaasgevind het nie. Aansienlike radiosensitiwiteit is waargeneem toe X-strale aangewend is 4 uur na EMV-blootstelling. MeWo-selle vooraf blootgestel aan 100Hz EMV en binne 6 uur opgevolg met bestraling, het opmerklike sensitisering vir bestraling getoon. Behandeling van hierdie selle met ‘n 1000Hz-veldsterkte het egter die effek van X-strale aansienlik versterk. Toe selle bestraal is voor EMV-blootstelling, is die V79-selle marginaal deur die 100Hz-veld beskerm en gesensitiseer deur die 1000Hz-veld. In teenstelling is die melanoomselle tot ‘n mate beskerm deur die 1000Hz-veld en gesensitiseer deur die 100Hz-veld. Die oorlewingstempo van die normale fibroblaste behandel met 2Gy, in twee fraksies van 1Gy, ses uur na mekaar, was soortgelyk aan dié toe selle ‘n akute dosis van 2Gy ontvang het ses uur voor of na hul blootstelling aan beide EMV-frekwensies. In teenstelling, is die melanoomselle merkwaardig gesensitiseer toe hul behandel is met ‘n kombinasie van X-strale en dan 100Hz EMV ses uur later, of met ‘n kombinasie van die EMV-frekwensies en X-strale ses uur later. Hierdie data suggereer dat die gebruik van elektromagnetiese velde tumore gevoelig mag maak vir stralingsterapie, terwyl dit toksisiteit vir normale weefsel verminder. Ingeligte en weldeurdagte kombinasies van laagmediumfrekwensie elektromagnetiese velde en stralingsterapie mag moontlik voordelig wees vir die behandeling van maligniteite, veral epidemiese Kaposi-sarkoom.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/100190
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