Novel treatment strategies for breast, lung and cervical cancer

Hamid, Mogammad Baahith (2019-12)

Thesis (PhD)--Stellenbosch University, 2019.

Thesis

ENGLISH SUMMARY : Cancer continues to be a global health burden, especially in the economically developing regions. The complex nature of this cancer contributes to a range of clinical challenges. Breast, lung and cervical cancer are known to have the highest incidence and mortality rates globally. Although many therapeutic options are available to treat cancer, the efficacy of most therapies is hindered due to normal tissue toxicity and tumour resistance. Novel treatment strategies are thus warranted to address clinical challenges and significantly improve patient outcomes. More than 50% of cancer patients receive radiotherapy throughout their illness. DNA damage resulting in cell death, as a consequence of ionising radiation exposure, has assisted in clinical tumour management. However, inherent and acquired resistance as well as the manipulation of essential pathways, like cell metabolism, have aided cancer cells to evade the toxic effects of radiotherapy. Increasing the therapeutic window of this treatment modality may benefit a large number of patients. There is evidence to suggest that ionising radiation may activate cell survival signalling pathways. Targeting the components of these pathways may modify cell metabolism and significantly radiosensitise cancer cells. Therefore, combining targeted therapy and ionising radiation may be a viable therapeutic strategy. The objective of this study was to inhibit molecular targets of key pathways which regulate cell survival, and expose breast, lung, cervical cancer and normal cell lines to doses of radiation, so as to establish potential therapeutic targets that may be amenable to combined modality therapy, and formulate a cocktail of inhibitors to evaluate its radiosensitising capability and effect on cellular metabolic activity. In this study, clonogenic assays were performed to determine the relative sensitivity of 6 cell lines (cancer: MDA-MB-231 (breast), MCF-7 (breast), HeLa (cervix) and A549 (lung); apparently normal: L132 (lung) and MCF-12A (breast)) to ionising radiation and inhibitor therapy. Mathematic modelling was used to determine the mode of interaction between EGFR, PI3K/mTOR, and BcL-2 inhibitors, as well as, the modifying effects of inhibitors on the radiosensitivity and metabolic activity of the cell lines. This study found that potential therapeutic benefit might be obtained by treating MDA-MB-231, MCF-7, HeLa and A549 cells with X-rays. The MCF-7 cell line showed the highest potential of therapeutic benefit with a greater than 2-fold higher radiosensitivity, relative to the normal MCF-12A cells. The A549 cell line showed the lowest potential for therapeutic benefit, when compared with the L132 cell line. Inhibition of PI3K and mTOR with NVP-BEZ235 resulted in a significant therapeutic benefit for the lung and cervical cancer cell lines, minor therapeutic benefit in the MCF-7 cell line, and no benefit for the MDA-MB-231 cell line. Bcl-2 inhibition with ABT-263 had either no effect on the MDA-MB-231 and A549 cell lines or resulted in potential therapeutic benefits for MCF-7 and HeLa cell lines. Pre-treatment of breast (MDA-MB-231 and MCF-7) and lung (A549) cancer cell lines with a cocktail of an EGFR (AG-1478), PI3K/mTOR (NVP-BEZ235), or Bcl-2 (ABT-263) inhibitors had an enhancing effect on radiosensitivity and cellular metabolic activity. The same treatment provided radioprotection, and reduced the metabolic activity of the cervical cancer cell line, HeLa. These findings suggest that concurrent inhibition of EGFR, PI3K, mTOR, and Bcl-2 during radiotherapy might improve the treatment response of breast and lung cancer in patients. Future studies validating these findings for lower inhibitor concentrations might be more relevant in the clinical setting, as systemic toxicity is a major concern. A study exposing cells to fractionated radiotherapy, after inhibitor pre-treatment, may further reveal the therapeutic potential of the inhibitors used in this study. Evaluating the effect of inhibitor pre-treatment and radiofrequency field, which have been shown to exhibit radiomodulatory effects on cancer and normal cell lines, may provide insight into the development of a novel therapeutic strategy.

AFRIKAANSE OPSOMMING : Kanker is steeds 'n wêreldwye gesondheidslas, veral in die ekonomies ontwikkelende streke. Die ingewikkelde aard van kanker dra by tot 'n verskeidenheid kliniese uitdagings. Dit is bekend dat bors-, long- en servikale kanker wêreldwyd die hoogste voorkoms en sterftesyfers het. Alhoewel daar baie terapeutiese opsies beskikbaar is om kanker te behandel, word die doeltreffendheid van die meeste terapieë ingeboet weens normale weefseltoksisiteit en gewasweerstand. Nuwe behandelingsstrategieë sal dus in alle waarskynlikheid kliniese uitdagings aanspreek en pasiëntuitkomste beduidend verbeter. Meer as 50% van kankerpasiënte ontvang radioterapie regdeur hul siekte. DNA-skade as gevolg van blootstelling aan ioniserende bestraling, wat lei tot seldood, het gehelp met die beheer van kliniese gewasse. Inherente en verworwe weerstand en die manipulering van noodsaaklike paaie, soos selmetabolisme, het kankerselle egter gehelp om die giftige effekte van radioterapie te ontduik. Die vergroting van die terapeutiese venster van hierdie behandelingsmodaliteit kan moontlik 'n groot aantal pasiënte bevoordeel. Daar is bewyse wat daarop dui dat ioniserende bestraling selle se oorlewingseingewingpaaie kan aktiveer. Die teikening van die komponente van hierdie paaie kan selmetabolisme moontlik verander en kankerselle beduidend sensitiseer vir radioterapie. Daarom kan die kombinasie van geteikende terapie en ioniserende bestraling 'n haalbare terapeutiese strategie wees. Die doel van hierdie studie was om molekulêre teikens van sleutelpaaie wat seloorlewing reguleer, te inhibeer, en bors-, long-, servikale kanker en normale sellyne bloot te stel aan dosisse bestraling, om moontlike terapeutiese teikens daar te stel wat geskik is vir gekombineerde modaliteitsterapie, en 'n mengsel van inhibeerders te formuleer om die radiosensitiserende-vermoë en effek daarvan op sellulêre metaboliese aktiwiteit te evalueer. In hierdie studie is klonogene ondersoeke uitgevoer om die relatiewe sensitiwiteit van 6 sellyne (kanker: MDA-MB-231 (bors), MCF-7 (bors), HeLa (serviks) en A549 (long) te bepaal; blykbaar normaal: L132 (long) en MCF-12A (bors)) tot ioniserende bestraling en inhibitorterapie. Wiskundige modellering is gebruik om die interaksiemodus tussen EGFR, PI3K / mTOR en BcL-2-inhibitors te bepaal, sowel as die modifiserende effekte van inhibitors op die radiosensitiwiteit en metaboliese aktiwiteit van die sellyne. Hierdie studie het bevind dat potensiële terapeutiese voordele verkry kan word deur MDA-MB-231, MCF-7, HeLa en A549 selle met X-strale te behandel. Die MCF-7- sellyn het die grootste potensiaal vir terapeutiese voordele getoon met 'n meer as twee keer hoër radiosensitiwiteit, relatief tot die normale MCF-12A-selle. Die A549-sellyn het die laagste potensiaal vir terapeutiese voordele getoon in vergelyking met die L132-sellyn. Die inhibering van PI3K en mTOR met NVP-BEZ235 het 'n beduidende terapeutiese voordeel ingehou vir die long- en servikale kankersellyne, geringe terapeutiese voordele in die MCF-7-sellyn, en geen voordeel vir die MDAMB-231-sellyn nie. Bcl-2-inhibering met ABT-263 het óf geen effek op die MDA-MB-231 en A549-sellyne gehad nie, óf dit het potensiële terapeutiese voordele vir MCF-7- en HeLa-sellyne ingehou. Voorbehandeling van bors- (MDA-MB-231 en MCF-7) en long(A549)-kankerselle met 'n mengsel van 'n EGFR (AG-1478), PI3K/mTOR (NVP-BEZ235), of Bcl-2 (ABT-263) inhibeerders het 'n verhoogde uitwerking op radiosensitiwiteit en sellulêre metaboliese aktiwiteit gehad. Dieselfde behandeling het radiobeskerming en verlaagde metaboliese aktiwiteit van die servikale kankersellyn, HeLa, gebied. Hierdie bevindings dui daarop dat gelyktydige inhibering van EGFR, PI3K, mTOR en Bcl-2 tydens radioterapie die behandelingsrespons van bors- en longkanker by pasiënte kan verbeter. Toekomstige studies wat hierdie bevindings vir laer inhibitorkonsentrasie bevestig, kan meer relevant in die kliniese omgewing wees, aangesien sistemiese toksisiteit 'n groot bron van kommer is. 'n Studie wat selle blootstel aan gefraksioneerde radioterapie, ná voorbehandeling van die inhibitor, kan moontlik die terapeutiese potensiaal van die inhibitors wat in hierdie studie gebruik is, openbaar. Evaluering van die effek van inhibitorvoorbehandeling en radiofrekwensieveld, wat getoon het dat dit radiomodulatoriese effekte op kanker en normale sellyne kan hê, kan insig bied in die ontwikkeling van 'n nuwe terapeutiese strategie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/107190
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