role of tumor microenvironment on HIF-1 pathway modulation and its association to photodynamic resistance

LAMBERTI MARÍA JULIA; RUMIE VITTAR NATALIA BELEN; RIVAROLA VIVIANA A

coimbra

Congreso; 16th world congress IPA; 2017

IPA

The tumor microenvironment (TME) undergoesextensive reciprocal interactions with the cancer cells and provides oncogenicsignals that exacerbate cancer progression. One of themost important aspects of the TME crosstalk is the ability of cancer cells tomodulate stroma behavior, and vice versa, through the collective action of avariety of soluble mediators which constitute ?cancer secretome?1. Photodynamic therapy (PDT), a promising treatment option forcancer, involves the combination of photosensitizing agents (PS), O2and light to create a harmful photochemical reaction mediated by reactiveoxygen species (ROS)2. Recent observationsemphasize the role that the TME plays in drug resistance in general and to PDTin particular, strongly suggesting that the mechanical properties and stromalcellular component need to be taken into account in order to improve efficacyof anticancer therapies3. Thus,we aimed to examine the molecular and biological mechanisms underlyingresistance to PDT. In order to recapitulate tumor architecture of therespective original tumor, we developed a multicellular three-dimensional (3D) spheroidco-culture system comprising tumor cells (SW480, TC) and stromal fibroblastscells (MRC-5, FC). 3D-spheroids exhibited a normoxic periphery surrounding ahypoxic core. The characterization of the homotypic (TC) and heterotypic(TC+FC) spheroids´ secretomes was performed using label-free LC?MS.Bioinformatic analysis using PID database revealed that HIF-1 signaling pathwaywas the most highly enriched within the proteins whose secretion was enhancedin heterotypic spheroids. HIF-1 is a key transcriptional mediator of metabolicadaptation and VEGF-mediated angiogenesis in response to hypoxia4. Using Me-ALA, a prodrug of the PS PpIX, HIF-1 transcriptionalactivity was strongly up-regulated and mediated PDT resistant phenotype inhuman colorectal spheroids. RNAi knockdown of HIF-1 impaired resistance to PDT.Oxidative stress-mediated activation of ERK1/2 followed PDT was involved onpositive modulation of HIF-1 transcriptional activity after photosensitization.ROS scavenging and MEK/ERK pathway inhibition abrogated the PDT-mediated HIF-1upregulation. Together our data demonstrated that resistance to PDT is in partmediated by the activation of a ROS-ERK1/2-HIF-1 axis, thus, identifying noveltherapeutic targets that could be used in combination with PDT. Consistently,the presence of FCs considerably diminished TCs sensitivity to photodynamicactivity. HIF-1 pathway modulation by both PDT and FC was further confirmedthrough the evaluation of the expression of the HIF-target gene VEGF.Collectively, our results delineated a mechanism by which FCs enhance TCssurvival and treatment resistance, which can potentially guide translationalresearch specifically aimed at effective clinical interventions forfibroblast-enriched and consequently HIF-1 pathway overexpressing tumors.