The gene for Pregnancy Up-regulated Non-ubiquitous Calmodulin Kinase (Pnck), a novel calmodulin kinase, is expressed in roughly one-third of human breast tumors, but not in adjoining normal tissues. Pnck alters EGFR stability and function, prompting this study to determine if Pnck expression has implications for HER-2 function and HER-2-directed therapy. The frequency of Pnck expression in HER-2-amplified breast cancer was examined by immunohistochemistry, and the impact of Pnck expression in the presence of HER-2 amplification on cancer cell proliferation, clonogenicity, cell-cycle progression, and Trastuzumab sensitivity was examined in vitro by transfection of cells with Pnck. Cell signaling was probed by Western blot analysis and shRNA-mediated PTEN knockdown. Over 30 % of HER-2 amplified tumors were found to express Pnck. Expression of Pnck in SkBr3 cells resulted in increased proliferation, clonal growth, cell-cycle progression, and Trastuzumab resistance. Pnck expression increases Hsp27 expression, Trastuzumab partial agonist activity on HER-2 Y1248 phosphorylation, and suppressed extracellular signal-regulated kinase (ERK1/2) activity. Knockdown of endogenous PTEN upregulated ERK1/2 activity, inhibited cellular proliferation, and partially sensitized Pnck/SKBr3 cells to Trastuzumab treatment. Increased proliferation of the Pnck/SKBr3 cells was observed following expression of protein phosphatase active and lipid phosphatase dead PTEN mutant but not the total phosphatase dead PTEN mutant. Co-overexpression of HER-2 and Pnck results in enhanced tumor cell proliferation and Trastuzumab resistance that is paradoxically dependent on PTEN protein phosphatase activity. This suggests that Pnck may be a marker of Trastuzumab resistance and possibly a therapeutic target.
BackgroundRadiation therapy is an indispensable part of various treatment modalities for breast cancer. Specifically, for non-inflammatory locally advanced breast cancer (LABC) patients, preoperative radiotherapy (pRT) is currently indicated as a second line therapy in the event of lack of response to neoadjuvant chemotherapy. Still approximately one third of patients fails to respond favourably to pRT. The aim of this study was to explore molecular mechanisms underlying differential response to radiotherapy (RT) to identify predictive biomarkers and potential targets for increasing radiosensitivity.MethodsThe study was based on a cohort of 134 LABC patients, treated at the Institute of Oncology and Radiology of Serbia (IORS) with pRT, without previous or concomitant systemic therapy. Baseline transcriptional profiles were established using Agilent 60 K microarray platform in a subset of 23 formalin-fixed paraffin-embedded (FFPE) LABC tumour samples of which 11 radiotherapy naïve and 3 post-radiotherapy samples passed quality control and were used for downstream analysis. Biological networks and signalling pathways underlying differential response to RT were identified using Ingenuity Pathways Analysis software. Predictive value of candidate genes in the preoperative setting was further validated by qRT-PCR in an independent subset of 60 LABC samples of which 42 had sufficient quality for data analysis, and in postoperative setting using microarray data from 344 node-negative breast cancer patients (Erasmus cohort, GSE2034 and GSE5327) treated either with surgery only (20%) or surgery with RT (80%).ResultsWe identified 192 significantly differentially expressed genes (FDR < 0.10) between pRT-responsive and non-responsive tumours, related to regulation of cellular development, growth and proliferation, cell cycle control of chromosomal replication, glucose metabolism and NAD biosynthesis II route. APOA1, MAP3K4, and MMP14 genes were differentially expressed (FDR < 0.20) between pRT responders and non-responders in preoperative setting, while MAP3K4 was further validated as RT-specific predictive biomarker of distant metastasis free survival (HR = 2.54, [95%CI:1.42–4.55], p = 0.002) in the postoperative setting.ConclusionsThis study pinpoints MAP3K4 as a putative biomarker of response to RT in both preoperative and postoperative settings and a potential target for radiosensitising combination therapy, warranting further pre-clinical studies and prospective clinical validation.Electronic supplementary materialThe online version of this article (10.1186/s13014-018-1129-4) contains supplementary material, which is available to authorized users.
The results suggest that the RAD51 G135C and XRCC1 Arg399Gln polymorphisms could be biomarkers of susceptibility for ovarian carcinoma development. Further larger case-control study is needed to confirm our findings.
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