Investigating inhibition of porphyrin (heme) synthesis as a novel treatment option for prostate cancer

Prostate cancer (PC) affects 1 in 8 men in the UK. Hormone therapy is used to initially treat men diagnosed with non-organ confined disease. PC growth is dependent upon the androgen receptor and hence therapies for non-organ confined disease aim to disrupt this signalling axis. However, over time cancer cells adapt and become therapy resistant. For this stage of the disease, there are limited treatment options and there is a need for new therapies that can target these resistant forms of PC. Metabolism is a process often modified in cancer cells. It has been shown that porphyrin synthesis is increased in multiple cancers and targeting this pathway may be a viable treatment option for PC. Crystal violet assays demonstrated that the porphyrin synthesis inhibitor succinyl acetone (SA) reduced the proliferation of PC3, LNCaP and DU145 cells and heme depletion assays confirmed that SA does decrease cellular heme content. Flow cytometry demonstrated that SA induced a low level of caspase independent cell death, but when combined with ROS damage the percentage number of cells undergoing cell death increased significantly. The data suggest that cell death is not as a result of apoptosis, necroptosis or ferroptosis, suggesting a different type of cell death is occurring. This study also aimed to express and purify the enzymes responsible for the first step in heme synthesis, performed by ALAS 1 or 2. ALAS 2 T was able to be purified in Rosetta cells in a pET28a vector and ALAS 1 T was expressed in pET21a vector in T7 shuffle cells. Heme synthesis was further validated as a novel therapeutic target for PC and the successful expression of ALAS1 and 2 will facilitate future drug discovery programs.