Abstract C146: Radiation-inducible molecular targets in a human prostate cancer mouse model

Background: In order to understand the changes induced in tumor cells following multi-fraction (MF) radiation therapy, we have previously studied molecular changes using prostate cancer cells and endothelial cells treated in vitro with MF doses of 0.5 Gy/1 Gy x 10 and 2 Gy x 5 and single-dose (SD) of 5 Gy and 10 Gy. The hypothesis being tested is that the response and adaptation to radiation-induced stress will produce a druggable phenotype. This might increase the utility of molecularly targeted therapeutics and also help address tumor cell heterogeneity. The data indicate more genes and pathways are induced by MF compared to SD and that the change in phenotype is more stable following MF. In this report, the focus is on new data from PC-3 cells irradiated in vivo and comparing it to MF and SD in vitro using MF 1 Gy x 10 and SD 10 Gy. Methods: PC-3 prostate cancer cells were implanted subcutaneously into the lateral aspect of rear leg of nude mice. Mice were divided into three groups (n = 3), based on radiation dose/schedule- control, SD, and MF. SD and MF employed similar dose/schedule as used for the in vitro studies, 10 Gy x 1 and 1 Gy x 10 respectively. RNA was isolated 24 h after radiation treatment. mRNA microarray analysis was performed using Agilent Technologies Human Gene Expression 4 × 44 K V2 microarrays. The data was generated and analyzed with GeneSpring® software (Agilent Technologies, Santa Clara, CA) and IPA software (IPA, QIAGEN, Redwood City, CA). Results: 6,374 genes were significantly altered by MF, with a cohort of genes, based on the > 250 gene ontology categories, involved in DNA response to stimulus, DNA repair, mitosis, cell cycle, and metabolism. In contrast, only 453 genes were significantly altered by SD, with ontological categories associated with cell morphology, assembly and organization such as actin filament-based process, extracellular matrix organization and biogenesis, fibril organization and biogenesis and collagen catabolism. Further bioinformatics analysis of the gene expression data with IPA, identified multiple pathways with functions correlated with the ontological categories. Significantly altered MF-induced genes are members of pathways which play a central role in DNA replication, recombination, and repair, cell proliferation and metabolism such as HIPPO Signaling, Protein Ubiquitination Pathway, JNK/SAPK Signaling, ERK/MAPK Signaling, G2/M DNA Damage Checkpoint Regulation, ATM Signaling, PI3K/AKT Signaling and Oxidative Phosphorylation. These pathways were uniquely up-regulated by MF treatment, as none of these changes were identified with SD radiation exposure. Conclusion: Our result show the differential expression pattern between SD and MF, with MF inducing changes in “targetable” molecular pathways. Ongoing studies: Currently we are in the process of evaluating radiation-induced targets in ATM signaling, DNA damage and repair, and multiple metabolic targets, and their potential for using radiation to prime cells for molecular-targeted drug therapy. Citation Format: Adeola Y. Makinde, Iris Eke, Molykutty J. Aryankalayil, Mansoor Ahmed, C. Norman Coleman. Radiation-inducible molecular targets in a human prostate cancer mouse model. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C146.