Assessing the effects of vitamin D as a regulator of androgen intracrinology in prostate cancer using mass spectrometry imaging

Abstract

Castrate resistant prostate cancer (CRPC) relies on the supply of potent androgens such as dihydrotestosterone (DHT) from intratumoral conversion from the precursor dehydroepiandrosterone (DHEA) for growth. Vitamin D has been proposed as a chemotherapeutic agent by way of vitamin D receptor(VDR) activation. The mechanistic enzymes of the intracrine pathway are influenced by VDR activation and thus can have a beneficial effect of the outcome of androgen synthesis, by reducing the active androgens produced. In this thesis, I aimed to explore the metabolic outcomes of vitamin D treatment upon a CRPC translation model, by assessing the androgen intracrine conversions using mass spectrometry-based techniques and genetic changes. Employing an in vitro based assay, effects of vitamin D treatment were assessed for metabolic changes within the CRPC steroid pathway, using a semiquantitative method. Further evaluation of key metabolic gene changes was also undertaken. Findings confirm that vitamin D treatment decreased the levels of potent androgens, with increased hydroxylation, linked to the upregulation of the gene CYP3A4.

An in vivo prostate cancer xenograft was also evaluated for vitamin D treatment upon castration and DHEA introduction. Spatial distribution of endogenous androgens in prostatic cancerous tissue were assessed using mass spectrometry imaging. A method of chemical derivatisation for neutral endogenous androgens was developed using the ImagePrep device, enhancing ionisation efficiency for on-tissue analysis. Biological assays were also employed to determine any effects exhibited by the vitamin D treatment, such agene expression analysis and total androgen quantitation. Vitamin D was found to induce changes in slowing growth and lowering levels of potent androgens. To further explore vitamin D treatment assay capabilities, a novel chemical derivatisation method for mass spectrometry imaging was developed by screening numerous reagents for off and on-tissue analysis. Ion efficiency was enhanced for on-tissue endogenous vitamin D metabolites with successful imaging of derivatised 25-(OH)-D2 and 1,25-(OH)2-D3 in mouse kidneys.

Thesis is embargoed until 31st March 2022

Date of Award	Mar 2020
Original language	English
Supervisor	Diego Cobice (Supervisor) & Paul Thompson (Supervisor)