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MINI 21 - Novel Targets (ID 133)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Biology, Pathology, and Molecular Testing
- Presentations: 1
MINI21.01 - Purinergic Signaling in NSCLC - First in Vivo Data and Potential Therapeutic Targets (ID 166)
16:45 - 18:15 | Author(s): B. Haager
Purines are well known as intracellular sources for energy but also act as extracellular signaling molecules. In the last decade there has been a growing interest in the therapeutic potential of purinergic signaling for cancer treatment. The effects carried out depend on the concentration, expressed pattern of purinergic receptors and general dynamics of synthesis and degradation. In this study we analyze different purines and purinergic receptors in bronchoalveolar lavage (BAL) of patients with non-small-cell lung cancer (NSCLC) to provide further insight on their relevance in the tumor microenvironment.
In this prospective clinical trial we enrolled 27 patients with NSCLC and 16 patients with chronic obstructive pulmonary disease (COPD) without signs of malignancy. The study was approved by our local ethics committee and registered as a clinical trial in the German Registry for Clinical Trials (DRKS-ID: DRKS00005415). BAL was performed using flexible bronchoscopes. The bronchoscope was wedged into a subsegment were the tumor was present and a total of 300 ml sterile saline was instilled. The BAL-fluid (BALF) was recovered by gentle aspiration. Purines (ATP, ADP, AMP, Adenosine and Inosine) were analyzed using fluorescence/luminescence based assays. Expression of purinergic receptors and Ectonucleotidases in NSCLC (P2X1, P2X4, P2X7, P2Y1, P2Y2, P2Y4, P2Y6, P2Y12, P2Y13, P2Y14, CD39, CD73) were analyzed using qPCR.
Patients with NSCLC have significantly lower ATP and ADP concentrations in BALF than patients with COPD without signs of malignancy (p=0.006 and p=0.009). Inosine concentrations however are higher in patients with malignant disease (p=0.01). In the subgroup-analysis of metastasized versus non-metastasized tumors receptor-analysis revealed a higher expression of P2X4 (p=0.07), P2X7 (p=0.0008) and P2Y1 (p=0.009) as well as of the ectonucleotidase CD39 (p=0.007). Analysis of the purine metabolites in the respective groups showed no statistically significant differences. Furthermore there is a positive correlation of the proportion of macrophages in differential cell count in BAL with the expression of P2X7 (r=0.53, p=0.02).
Previous data suggests pro-inflammatory, zytotoxic and thus anti-neoplastic effects of Adenosine-Triphosphate (ATP) and ADP. Also it has been shown that low ATP concentrations in the tumor microenvironment can lead to enhanced proliferation of tumor cells. In this first in vivo study on purinergic signaling in lung cancer we find lower concentrations of ATP and ADP in samples from NSCLC patients compared to COPD without signs of malignancy in accordance with these findings. Furthermore in aggressive, metastasized NSCLC we find a higher expression of the ectonucleotidase CD39. This enzyme degrades ATP and ADP to Adenosin and has previously been shown to hence induce immune escape in malignant disease. Furthermore we demonstrate elevated expression of P2X4, P2X7 and P2Y1 in the tumor microenvironment of metastasized NSCLC compared to non-metastasized tumors. This suggests a role of these receptors in tumor metastasis, however the exact mechanisms remain unclear. To further illustrate these interactions we are currently initiating a study to identify purinergic receptors in NSCLC tumor cells from pathologic specimen. With this knowledge future translational studies can be conducted to potentially provide new therapeutic targets.
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