Ionizing radiation, but not stimulation with epidermal growth factor (EGF), triggers EGF receptor (EGFR) import into the nucleus in a probably karyopherin ␣-linked manner. An increase in nuclear EGFR is also observed after treatment with H 2 O 2 , heat, or cisplatin. During this process, the proteins Ku70/80 and the protein phosphatase 1 are transported into the nucleus. As a consequence, an increase in the nuclear kinase activity of DNA-dependent kinase (DNA-PK) and increased formation of the DNA end-binding protein complexes containing DNA-PK, essential for repair of DNA-strand breaks, occurred. Blockade of EGFR import by the anti-EGFR monoclonal antibody C225 abolished EGFR import into the nucleus and radiation-induced activation of DNA-PK, inhibited DNA repair, and increased radiosensitivity of treated cells. Our data implicate a novel function of the EGFR during DNA repair processes.The epidermal growth factor receptor (EGFR) 1 is essential for mediation of both proliferative and survival signals to cells (1). At least five mitogenic growth factors bind to and activate EGFR. In addition to EGF these factors include transforming growth factor-␣, amphiregulin, heparin binding EGF (2), and epiregulin (3). Moreover, in recent years it became apparent that in addition to ligand binding-induced activation of the EGFR, ligand-independent receptor activating processes also exist (4). Activation of the EGFR signaling pathway by ligands has been linked with increased cell proliferation, angiogenesis, and metastasis and decreased apoptosis (5). As a consequence it is assumed that increased EGFR signaling plays an important role in tumorigenesis (6, 7). The mechanisms of ligand-independent EGFR activation and also the importance for the cell fate are not understood so far. But it is noteworthy that the ligand-independent activation always is linked to exposure to genotoxic stress (4,8,9). However, the differences of the observed cell response after ligand-induced EGFR activation, e.g. cell proliferation, and ligandindependent activation, e.g. cell cycle arrest, argue rather for a link to DNA repair processes for ligand-independent activation. This idea was strengthened by the observation that many tumor cells show an increased radiosensitivity after inhibition of EGFR signaling (10). The most detrimental DNA damages after treatment with ionizing radiation are double-strand strands (11), which are preferentially repaired in mammalians by nonhomologous end-joining (12). Looking for a connection between radiation-induced EGFR activation and DNA repair, we found a report stating that there is a physical interaction of EGFR and DNAdependent kinase (DNA-PK) (13) after cell treatment with the EGFR blocking antibody C225. As a consequence, the nuclear DNA-PK protein and activity was reduced, providing an explanation for the radiosensitizing effect of the EGFR blockage. However, this paper did not answer the question of the functional role of the physical interaction between EGFR and DNA-PK. Therefore, we addressed herein the...

Radiation therapy plays an important role in the management of prostate carcinoma. However, the problem of radioresistance and molecular mechanisms by which prostate carcinoma cells overcome cytotoxic effects of radiation therapy remains to be elucidated. In order to investigate possible intracellular mechanisms underlying the prostate carcinoma recurrences after radiotherapy, we have established three radiation-resistant prostate cancer cell lines, LNCaP-IRR, PC3-IRR, and Du145-IRR derived from the parental LNCaP, PC3, and Du145 prostate cancer cells by repetitive exposure to ionizing radiation. LNCaP-IRR, PC3-IRR, and Du145-IRR cells (prostate carcinoma cells recurred after radiation exposure (IRR cells)) showed higher radioresistance and cell motility than parental cell lines. IRR cells exhibited higher levels of androgen and epidermal growth factor (EGF) receptors and activation of their downstream pathways, such as Ras-mitogen-activated protein kinase (MAPK) and phosphatidyl inositol 3-kinase (PI3K)-Akt and Jak-STAT. In order to define additional mechanisms involved in the radioresistance development, we determined differences in the proteome profile of parental and IRR cells using 2-D DIGE followed by computational image analysis and MS. Twenty-seven proteins were found to be modulated in all three radioresistant cell lines compared to parental cells. Identified proteins revealed capacity to interact with EGF and androgen receptors related signal transduction pathways and were involved in the regulation of intracellular routs providing cell survival, increased motility, mutagenesis, and DNA repair. Our data suggest that radioresistance development is accompanied by multiple mechanisms, including activation of cell receptors and related downstream signal transduction pathways. Identified proteins regulated in the radioresistant prostate carcinoma cells can significantly intensify activation of intracellular signaling that govern cell survival, growth, proliferation, invasion, motility, and DNA repair. In addition, such analyses may be utilized in predicting cellular response to radiotherapy.

SummaryWe assessed the association of postmenopausal serum levels of oestrogens and sex hormone-binding globulin (SHBG) with endometrial cancer risk in a case-control study nested within the NYU Women's Health Study cohort. Among 7054 women postmenopausal at enrolment, 57 cases of endometrial cancer were diagnosed a median of 5.5 years after blood donation. Each case was compared to 4 controls matched on age, menopausal status at enrolment, and serum storage duration. Endometrial cancer risk increased with higher levels of oestradiol (odds ratio = 2.4 in highest vs lowest tertile, P for trend = 0.02), percent free oestradiol (OR = 3.5, P < 0.001), and oestrone (OR = 3.9, P < 0.001). Risk decreased with higher levels of percent SHBG-bound oestradiol (OR = 0.43, P = 0.03) and SHBG (OR = 0.39, P = 0.01). Trends remained in the same directions after adjusting for height and body mass index. A positive association of body mass index with risk was substantially reduced after adjusting for oestrone level. Our results indicate that risk of endometrial cancer increases with increasing postmenopausal oestrogen levels but do not provide strong support for a role of body mass index independent of its effect on oestrogen levels.

Ipilimumab is effective for patients with melanoma, but not for those with less immunogenic tumors. We report a phase II trial of ipilimumab with concurrent or sequential stereotactic ablative radiotherapy to metastatic lesions in the liver or lung (NCT02239900). Ipilimumab (every 3 weeks for 4 doses) was given with radiotherapy begun during the first dose (concurrent) or 1 week after the second dose (sequential) and delivered as 50 Gy in 4 fractions or 60 Gy in 10 fractions to metastatic liver or lung lesions. In total, 106 patients received !1 cycle of ipilimumab with radiation. Median follow-up was 10.5 months. Median progression-free survival time was 2.9 months (95% confidence interval, 2.45-3.40), and median overall survival time was not reached. Rates of clinical benefit of nonirradiated tumor volume were 26% overall, 28% for sequential versus 20% for concurrent therapy (P ¼ 0.250), and 31% for lung versus 14% for liver metastases (P ¼ 0.061). The sequential lung group had the highest rate of clinical benefit at 42%. There were no differences in treatment-related adverse events between groups. Exploratory analysis of nontargeted lesions revealed that lesions receiving low-dose radiation were more likely to respond than those that received no radiation (31% vs. 5%, P ¼ 0.0091). This phase II trial of ipilimumab with stereotactic radiotherapy describes satisfactory outcomes and low toxicities, lending support to further investigation of combined-modality therapy for metastatic cancers.

No abstract