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During S phase, the cooperation between the macromolecular complexes regulating DNA synthesis, epigenetic information maintenance and DNA repair is advantageous for cells, as they can rapidly detect DNA damage and initiate the DNA damage response (DDR). UHRF1 is a fundamental epigenetic regulator; its ability to coordinate DNA methylation and histone code is unique across proteomes of different species. Recently, UHRF1’s role in DNA damage repair has been explored and recognized to be as important as its role in maintaining the epigenome. UHRF1 is a sensor for interstrand crosslinks and a determinant for the switch towards homologous recombination in the repair of double-strand breaks; its loss results in enhanced sensitivity to DNA damage. These functions are finely regulated by specific post-translational modifications and are mediated by the SRA domain, which binds to damaged DNA, and the RING domain. Here, we review recent studies on the role of UHRF1 in DDR focusing on how it recognizes DNA damage and cooperates with other proteins in its repair. We then discuss how UHRF1’s epigenetic abilities in reading and writing histone modifications, or its interactions with ncRNAs, could interlace with its role in DDR.

Epithelial-to-mesenchymal transition (EMT) is involved in prostate cancer (PCa) metastatic progression, and its plasticity suggests epigenetic implications. Deregulation of DNA methyltransferases (DNMTs) and several microRNAs (miRNAs) plays a relevant role in EMT, but their interplay has not been clarified yet. In this study, we provide evidence that DNMT3A interaction with several miRNAs has a central role in an ex vivo EMT PCa model obtained via exposure of PC3 cells to conditioned media from cancer-associated fibroblasts. The analysis of the alterations of the miRNA profile shows that miR-200 family (miR-200a/200b/429, miR-200c/141), miR-205 and miR-203, known to modulate key EMT factors, are down-regulated and hyper-methylated at their promoters. DNMT3A (mainly isoform a) is recruited onto these miRNA promoters, coupled with the increase of H3K27me3/H3K9me3 and/or the decrease of H3K4me3/H3K36me3. Most interestingly, our results reveal the differential expression of two DNMT3A isoforms (a and b) during ex vivo EMT and a regulatory feedback loop between miR-429 and DNMT3A that can promote and sustain the transition towards a more mesenchymal phenotype. We demonstrate the ability of miR-429 to target DNMT3A 3′UTR and modulate the expression of EMT factors, in particular ZEB1. Survey of the PRAD-TCGA dataset shows that patients expressing an EMT-like signature are indeed characterized by down-regulation of the same miRNAs with a diffused hyper-methylation at miR-200c/141 and miR-200a/200b/429 promoters. Finally, we show that miR-1260a also targets DNMT3A, although it does not seem to be involved in EMT in PCa.

Non-coding RNAs (ncRNAs) transcribed from the promoter and the downstream region can affect the expression of the corresponding coding genes. It has been shown that sense-directed ncRNAs arising from the promoter region of the E-cadherin gene (CDH1) mediate its repression. Here, we show that an antisense-directed ncRNA (paRCDH1-AS) transcribed from the CDH1 promoter is necessary for its expression. paRCDH1-AS acts as a hooking scaffold by recruiting the epigenetic regulators, UHRF1, DNMT3A, SUV39H1 and SUZ12, involved in CDH1 repression. The binding of epigenetic regulators to paCRDH1-AS, indeed, prevents their localization to the chromatin on CDH1 promoter. Moreover, paRCDH1-AS silencing induces CDH1 repression and a switch of the epigenetic profile on the promoter towards a more closed chromatin. Using bioinformatic and experimental approaches we defined that the promoter of the paRCDH1-AS is shared with the E-cadherin gene, showing a bidirectional promoter activity. We found that UHRF1 controls both CDH1 and paRCDH1-AS by directly binding this bidirectional promoter region. Our study provides evidences, for the first time, that UHRF1 recruitment can be affected by promoter-associated non-coding RNAs, opening new perspective regarding the role of UHRF1 in these complex regulatory networks.

WOS:000452343100012; International audience; Background: Deinococcus radiodurans R1 (DR) survives conditions of extreme desiccation, irradiation and exposure to genotoxic chemicals, due to efficient DNA breaks repair, also through Mn2+ protection of DNA repair enzymes. Methods: Possible annotated domains of the DR1533 locus protein (Shp) were searched by bioinformatic analysis. The gene was cloned and expressed as fusion protein. Band-shift assays of Shp or the SRA and HNH domains were performed on oligonucleotides, genomic DNA from E. coif and DR. slip knock-out mutant was generated by homologous recombination with a kanamycin resistance cassette. Results: DR1533 contains an N-terminal SRA domain and a C-terminal HNH motif (SRA-HNH Protein, Shp). Through its SRA domain, Shp binds double-strand oligonucleotides containing 5mC and 5hmC, but also unmethylated and mismatched cytosines in presence of Mn2+. Shp also binds to Escherichia coli dcm(+) genomic DNA, and to cytosine unmethylated DR and E. coli dcm(-) genomic DNAs, but only in presence of Mn2+. Under these binding conditions, Shp displays DNAse activity through its HNH domain. Shp KO enhanced \textgreater 100 fold the number of spontaneous mutants, whilst the treatment with DNA double strand break inducing agents enhanced up to 3-log the number of survivors. Conclusions: The SRA-HNH containing protein Shp binds to and cuts 5mC DNA, and unmethylated DNA in a Mn2+ dependent manner, and might be involved in faithful genome inheritance maintenance following DNA damage. General significance: Our results provide evidence for a potential role of DR Shp protein for genome integrity maintenance, following DNA double strand breaks induced by genotoxic agents.

Widespread genome hypo-methylation and promoter hyper-methylation of epithelium-specific genes are hallmarks of stable epithelial-to-mesenchymal transition (EMT), which in prostate cancer (PCa) correlates with castration resistance, cancer stem cells generation, chemoresistance and worst prognosis. Exploiting our consolidated 'ex-vivo' system, we show that cancer-associated fibroblasts (CAFs) released factors have pivotal roles in inducing genome methylation changes required for EMT and stemness in EMT-prone PCa cells. By global DNA methylation analysis and RNA-Seq, we provide compelling evidence that conditioned media from CAFs explanted from two unrelated patients with advanced PCa, stimulates concurrent DNA hypo- and hyper-methylation required for EMT and stemness in PC3 and DU145, but not in LN-CaP and its derivative C4-2B, PCa cells. CpG island (CGI) hyper-methylation associates with repression of genes required for epithelial maintenance and invasion antagonism, whereas activation of EMT markers and stemness genes correlate with CGI hypo-methylation. Remarkably, methylation variations and EMT-regulated transcripts almost completely reverse qualitatively and quantitatively during MET. Unsupervised clustering analysis of the PRAD TCGA data set with the differentially expressed (DE) and methylated EMT signature, identified a gene cluster of DE genes defined by a CAF+ and AR- phenotype and worst diagnosis. This gene cluster includes the relevant factors for EMT and stemness, which display DNA methylation variations in regulatory regions inversely correlated to their expression changes, thus strongly sustaining the ex-vivo data. DNMT3A-dependent methylation is essential for silencing epithelial maintenance and EMT counteracting genes, such as CDH1 and GRHL2, that is, the direct repressor of ZEB1, the key transcriptional factor for EMT and stemness. Accordingly, DNMT3A knock-down prevents EMT entry. These results shed light on the mechanisms of establishment and maintenance of coexisting DNA hypo- and hyper-methylation patterns during cancer progression, the generation of EMT and cell stemness in advanced PCa, and may pave the way to new therapeutic implications.

Brevundimonas vesicularis is a non-fermenting gram-negative bacillus, aerobic and motile. This microrganism is ubiquitous in the environment and has rarely been implicated in human infections. We present the second case of cutaneous infection caused by B. vesicularis in an immunocompetent patient.

Activation of hypoxia-inducible factor (HIF)-1 is a feature of hypoxic solid tumors that has been associated with drug resistance, mainly due to disruption of Bcl-2 family dynamics. Resetting the balance in favor of proapoptotic family members is an attractive therapeutic goal that has been pursued by developing BH3-mimetic compounds. In the present study we evaluated the response of human colon adenocarcinoma cells to the BH3-mimetic obatoclax (OBX), in terms of growth arrest, apoptosis and autophagy, in the presence or absence of HIF-1α-stabilizing conditions; its possible effect on HIF-1α expression and HIF-1 activity; and the possibility to improve the response of colon cancer cells to cytotoxic chemotherapeutics by combining them with OBX. Colon cancer cell response to the BH3-mimetic was unmodified by HIF-1 activation and OBX induced a decrease in HIF-1α protein levels and HIF-1 transcriptional activity, probably by decreasing HIF-1α synthesis and facilitating a VHL-independent proteasomal degradation pathway. Finally, a chemosensitizing effect of OBX with respect to 5-fluorouracil or oxaliplatin treatment was observed, highlighting the possibility that patients with hypoxic colon tumors might benefit from combined regimens including OBX.

Nonmelanoma skin cancers (NMSCs) are the most common type of skin tumor, representing about one-third of all malignancies diagnosed worldwide each year. Cutaneous squamous cell carcinoma (cSCC) is the second most common form of NMSCs and the risk of cSCC invasiveness should be assessed on the basis of tumor size, anatomical location, and histological subtype. Although most cSCCs are early diagnosed and successfully treated, in a small percentage of patients with giant cSCC (maximum diameter5 cm), metastases may occur; treatment options are limited and not really effective. We report the case of a giant metastatic cSCC that had been neglected for more than 20 years. Radiotherapy or surgery were not feasible and polichemotherapy (cisplatin, 5-fluorouracil and paclitaxel) was not effective. Therefore, the patient was treated with palliative electrochemotherapy (ECT) achieving a partial reduction of cutaneous metastasis and pain relief but unfortunately the patient died 3 months after the second ECT treatment.

Background: Metastatic triple-negative breast cancer is mostly incurable, due to lack of suitable drug targets. The insulin-like growth factor (IGF) system could provide such a target, and IGF-1 receptor (IGF-1R)-directed agents are already available, but seem unable to control all the complexities of the system, including crosstalk with hypoxia-inducible pathways. Methods: Migration of triple-negative MDA-231 breast cancer cells and its modulation by IGFs, the IGF-1R inhibitor NVP-AEW541 and the IGF-2-sequestering monoclonal antibody MAB292 were assessed by the scratch wound healing and Boyden chamber assays; the effect of topotecan (inhibiting hypoxia-inducible factor-1 (HIF-1)) under hypoxia was also evaluated. Constitutive as well as drug-modulated levels of components of the IGF and HIF-1 pathways were evaluated by western blotting and qPCR. Results: IGF-induced migration of MDA-231 cells was not abrogated by the IGF-1R inhibitor NVP-AEW541, whereas IGF-2 sequestration by MAB292 significantly reduced cell migration. Under hypoxia, topotecan was also effective, likely by reducing HIF-1-induced IGF-2 release. Simultaneous targeting of IGF-1R and IGF-2 or HIF-1 completely abolished cell migration. Conclusions: IR activation may account for the failure of NVP-AEW541 to suppress MDA-231 cell migration. Ligand-targeting compounds, or co-inhibition of the IGF and HIF-1 systems, may prevent activation of compensatory signalling, thereby providing a valuable addition to IGF-1R inhibitor-based therapies.

Dermoscopy allows early detection of melanoma also on acral volar skin. The majority of melanocytic nevi on palms and soles may show three major dermoscopic patterns: the parallel-furrow pattern, the lattice-like pattern, and the fibrillar pattern. Melanomas at these sites are characterized by the parallel ridge pattern. We present the case of a 59-year-old woman who had an oval papule of bluish color, measuring 0.6 x 0.9 cm, localized on her left sole, that had been present, unchanged, for more than 10 years. Dermoscopy showed a parallel ridge pattern. The histopathological examination revealed a combined blue nevus. We present this case to underline that on acral volar skin also intradermal nevi, such as combined blue nevi, may dermoscopically exhibit a parallel ridge pattern, simulating melanoma.

Among patients with cutaneous T-cell lymphoma (CTCL), sepsis and pulmonary infections are the first cause of death. We report on a patient with CTCL who, after more than 10 years of aggressive antineoplastic treatments, showed extensive pulmonary infiltrations on staging CT scan. Repeated CT scans were inconclusive for an infectious process, and the patient was still asymptomatic. The diagnosis of mycobacteriosis was made on the microbiologic exam of bronchoalveolar lavage. Specific treatment was started with contemporary dosage reduction of chemotherapy. After six months of antibiotic treatment the pulmonary lesions improved, whereas CTCL progressed. Therefore, a new antineoplastic regimen was started obtaining control of CTCL, without aggravation of the pulmonary lesions. We highlight the diagnostic and therapeutic pitfalls encountered when pulmonary mycobacteriosis complicates the course and treatment of CTCL.

Electrochemotherapy (ECT) is an emerging treatment for cutaneous lesions of different tumor types. The combination of chemotherapy and electroporation enhances drug uptake into tumoral cells. However, its role in the treatment of Kaposi sarcoma (KS) has not yet been well defined, and to date, literature reports are scarce. We prospectively evaluated clinical activity and safety of ECT in KS patients.Twenty-three patients with histologically confirmed unresectable KS, not treatable by radiotherapy or intralesional vincristine therapy, were enrolled onto the study according to the European Standard Operating Procedures of Electrochemotherapy (ESOPE) guidelines and treated with a pulse generator.A response to the first ECT session was obtained in all patients, with a complete response (CR) in 14 (60.9%) of 23 patients. A second ECT was performed in 5 (21.7%) and a third in 2, with a median interval between two sessions of 5.1 (range 2.5-25.5) months. Overall, a total of 15 patients (65%) experienced a CR. After a median follow-up of 1.5 years (range 2 months to 4.2 years), 16 patients maintained the response, 4 after repeated courses. Sustained local control of treated lesions was present in 20 of 23 patients. The overall survival rate was 74.4% at 2 years.ECT represents an additional therapeutic tool for the management of KS cutaneous lesions, characterized by a definite clinical activity and long-lasting remissions. The absence of systemic side effects and the low impact on the immune system also make this treatment suitable for elderly people, even with repeated courses.

Eight BODIPY dyes were synthesized and used as photosensitizers (PSs) on the human colon carcinoma cell line HCT116. In this panel of molecules, the structure varies in the substituents on pyrrole 2, 6 positions and on the phenyl ring at the indacene 8 position. For these compounds relevant physico-chemical parameters, such as singlet oxygen production, fluorescent quantum yield, absorbance profile and a relative rank of lipophilicity were determined. Our results indicate that some of these novel PSs are very effective in reducing the growth/viability of HCT116 cells when irradiated with a green LED source, whereas they are practically devoid of activity in the dark, up to 5 μM. To evaluate whether cell death is induced under these conditions, flow cytometric analysis of the percentage of apoptotic and autophagic cells was performed on four molecules, chosen for their efficacy/structural characteristics. Our data indicate that phototoxicity likely occurs mainly through apoptotic cell death, whereas autophagy seems to play a minor role in determining cell fate. Furthermore, the relationship between singlet oxygen generation and the PS efficacy is confirmed, thus underscoring the importance of the heavy-atom effect and of the presence of an aryl substituent at dipyrromethene 8 (meso) position. Among the PSs here described, the most efficient BODIPY was successfully tested on three other human cancer cell lines of different tissue origin, MCF7 (breast), A2780 and A2780/CP8 (ovary, sensitive and resistant to cisplatin, respectively), yielding IC(50) values comparable to those obtained on HCT116.

To investigate the radiosensitising effect of Ku autoantigen 70 (Ku70) and Ku autoantigen 80 (Ku80) knockdown by lentivirus-mediated RNA interference (RNAi) in the MCF10A immortalised human mammary epithelial cell line.MCF10A cells were infected with lentiviral vectors for RNAi of Ku70. The Ku70-knockdown cell line (Ku70i) and a mock-infected control cell line (LVTHM) were used to perform radiation experiments. For the in vitro Micronucleus (MN) assay, both cell lines were irradiated with doses of 2 and 4 Gy (60)Co gamma-rays. For cell survival experiments, doses ranging between 0 and 8 Gy were used.Western blot analysis showed that the Ku70 lentiviral vector was effective in silencing the expression of both Ku70 and Ku80. A significantly higher radiation-induced MN yield was obtained in the Ku70i cell line compared to the control LVTHM cell line. RNAi of Ku70 also resulted in a lower survival yield after irradiation compared to the control cell line. Analysis of cell death mechanisms showed that MCF10A cells (Ku70i and LVTHM) do not undergo apoptosis, but undergo post-irradiation cellular senescence.RNAi of Ku70 resulted in increased chromosomal and cellular radiosensitivity in the MCF10A human mammary cell line after irradiation with (60)Co gamma-rays. These results further strengthen the role of the Ku protein in correct DNA double strand break (DSB) repair.

Breast cancer patients are characterised by an enhanced chromosomal radiosensitivity pointing to a defect in the repair of DNA double strand breaks (dsb). In mammalian cells, radiation induced dsb are mainly repaired by the non homologous end-joining (NHEJ) repair pathway, a pathway in which the Ku70/Ku80 heterodimer plays a key role as it binds to the broken DNA ends. In this study we wanted to investigate the radiosensitizing effect of Ku70/80 knockdown, by lentivirus-mediated RNAinterference, in a spontaneous immortalised human mammary epithelial cell line (MCF10A). Several endpoints for measuring radiosensitivity were taken into acount: micronucleus formation (chromosomal radiosensitivity), cell survival, apoptosis and senescence. For all endpoints, MCF10A cells were infected with lentiviral vectors for RNAi of Ku70 (pLVTHM/shKu70/GFP). Western blot analysis showed that the Ku70 lentiviral vector was effective in silencing the expression of both Ku70 and Ku80. When a satisfactory knockdown was obtained (70-90% vs. mock-infected (pLVTHM/GFP) cells), the cells were used to perform radiation experiments. For the in vitro MN assay, cells were irradiated with doses of 2 and 4 Gy 60Co gamma-rays. A significantly higher radiation-induced MN yield was obtained in the Ku70/80 knock down cell line compared to the mock-infected cell line, pointing to an increased chromosomal radiosensitivity. This increased chromosomal radiosensitivity demonstrates that the repair genes, Ku70 and Ku80, are involved in the repair of DNA double strand breaks, which are the main DNA lesions resulting in chromosomal aberrations such as micronuclei. Besides chromosomal radiosensitivity we also investigated radiosensitivity at the cellular level by cell survival experiments. Cells were irradiated with doses ranging between 0 and 8 Gy and cultured for 5 days before being analysed. The results of the cell survival assay show that Ku70/80 knockdown cells have a lower survival yield after irradiation compared to mock-infected cells, pointing to an enhanced cellular radiosensitivity. Analysis of the cell death pattern showed that MCF10 cells (Ku70/80 knockdown and mock-infected) do not undergo apoptosis but go into cellular senescence. In conclusion, we can state that knockdown of Ku70 and Ku80 by RNAi of Ku70 resulted in an increased chromosomal and cellular radiosensitivity in an immortalised MCF10 human mammary cell line after irradiation with low LET 60Co gamma-rays. These results may further support the role of DNA dsb repair genes in breast cancer.

In the present study, we determined the incidence of dermatophyte species causing superficial mycoses among outpatients referred to the Department of Dermatology of the “La Sapienza” University of Rome between 2002 and 2004. Of the 3160 subjects studied, 1275 (40.3%) were positive for fungal infection, but only 252 (19.7%) of these had infections caused by dermatophytes. The dermatophyte most frequently isolated was Microsporum canis. Our epidemiological data were compared with those obtained previously by other authors in the same geographic area. For the first time we described an inversion of the T. rubrum/T. mentagrophytes ratio, the latter being more frequently encountered. We also observed the emergence of M. audouinii.

We present a patient with a cutaneous T-cell lymphoma/mycosis fungoides (CTCL/MF) followed for more than 10 years. After several different aggressive treatments to control progression of CTCL/MF, the patient developed several ulcerated tumors on the abdomen and limbs. Specific systemic antibiotic therapy failed to treat skin infection. While treating the stage III CTCL with polychemotherapy, we used an active colloidal hydrogel topically to manage wound healing and to treat and prevent potential sources of sepsis. After 11 weeks of treatment we observed complete cicatrization of ulcerated tumors. We reported on this case to describe the importance of a correct management of skin ulcers in immunosuppressed patients in order to avoid possible systemic spread of infection which represents the major cause of death in these patients.

Vocal reaction times (RTs) in naming 3- to 8-letter words were measured in proficient and dyslexic readers (Study 1). In proficient readers, RTs were independent of word length up to 5-letter words, indicating parallel processing. In the 5- to 8-letter range, RTs increased linearly, indicating sequential processing. Reading experience was associated with both faster discrimination of individual elements and parallel processing of increasingly large word parts. In dyslexics, RTs increased linearly with increasing length indicating reliance on sequential decoding. Individual analysis indicated 2 profiles of RTs (Types A and B). In Study 2, the distinction between A and B dyslexics was not associated with the use of different reading procedures. However, a more marked speed deficit characterized Type B dyslexics.

Interleukin-11 (IL-11) is a member of the IL-6 cytokine family, which mediate signaling via a common signal-transducing gp130 component and a cytokine-specific subunit (IL-11Rβ). Upon binding to the IL-11Rα, a signaling cascade activates several pathways, including JAK kinases, STAT transcription factors (STAT3 and STAT1), MAPK, src-family kinases and PI3K. IL-11 has been implicated in experimental models of chronic inflammation and associated tumorigenesis. Oncomine analysis of publicly available microarray data from patient biopsies showed that IL-11Rα mRNA is expressed in several sarcomas and not in the matched normal tissue counterparts. Surgical resection and cytotoxic chemotherapy are the standard of care for most locally advanced and metastatic sarcomas, the identification of new markers and the development of targeted therapies are needed to increase long-term survival of these patients. Previous studies demonstrated IL-11Rα is expressed in human primary and metastatic osteosarcomas but not in normal bone, suggesting that IL-11Rα is a potential target for sarcoma therapy. We analyzed a panel of 45 human sarcoma cell lines for the expression of IL-11Rα and IL-11. Interestingly, IL-11Rα protein is expressed at high levels in the majority of cell lines examined. In addition, we found that nearly all osteosarcoma, rhabdomyosarcoma, fibrosarcoma and Ewing sarcoma cell lines express high constitutive levels of IL-11 mRNA, indicating that IL-11 autocrine signaling may play a role in these tumor types. Two lentiviral vectors, used for the delivery of shRNA targeting IL-11 in HT-1080, produced an 80-90% decrease in IL-11 mRNA expression when compared to the luciferase control shRNA; however, IL-11 mRNA levels remained significantly high in HT1080 knock-down cells when compared to the constitutive levels of non sarcoma cancer types. Decreasing levels of IL-11 in HT-1080 resulted in a 50% inhibition of cell growth, demonstrating that IL-11 has a role in cell proliferation. Further experiments aimed to assess the expression of IL-11 and IL-11Rβ in xenografts and to explore the role of IL-11 in sarcoma pathogenesis, propagation and response to therapy are ongoing. These data suggest that neutralization of IL-11 or IL-11Rα may be a potential target for the development of cancer therapeutics for sarcomas. Funded by NCI Contract No. HHSN261200800001E. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 890. doi:1538-7445.AM2012-890

Background A better understanding of the underlying mechanisms of DNA repair after low- and high-LET radiations represents a research priority aimed at improving the outcome of clinical radiotherapy. To date however, our knowledge regarding the importance of DNA DSB repair proteins and mechanisms in the response of human cells to high-LET radiation, is far from being complete. Methods We investigated the radiosensitizing effect after interfering with the DNA repair capacity in a human mammary epithelial cell line (MCF10A) by lentiviral-mediated RNA interference (RNAi) of the Ku70 protein, a key-element of the nonhomologous end-joining (NHEJ) pathway. Following irradiation of control and Ku-deficient cell lines with either 6 MV X-rays or p(66)+Be(40) neutrons, cellular radiosensitivity testing was performed using a crystal violet cell proliferation assay. Chromosomal radiosensitivity was evaluated using the micronucleus (MN) assay. Results RNAi of Ku70 caused downregulation of both the Ku70 and the Ku80 proteins. This downregulation sensitized cells to both X-rays and neutrons. Comparable dose modifying factors (DMFs) for X-rays and neutrons of 1.62 and 1.52 respectively were obtained with the cell proliferation assay, which points to the similar involvement of the Ku heterodimer in the cellular response to both types of radiation beams. After using the MN assay to evaluate chromosomal radiosensitivity, the obtained DMFs for X-ray doses of 2 and 4 Gy were 2.95 and 2.66 respectively. After neutron irradiation, the DMFs for doses of 1 and 2 Gy were 3.36 and 2.82 respectively. The fact that DMFs are in the same range for X-rays and neutrons confirms a similar importance of the NHEJ pathway and the Ku heterodimer for repairing DNA damage induced by both X-rays and p(66)+Be(40) neutrons. Conclusions Interfering with the NHEJ pathway enhanced the radiosensitivity of human MCF10A cells to low-LET X-rays and high-LET neutrons, pointing to the importance of the Ku heterodimer for repairing damage induced by both types of radiation. Further research using other high-LET radiation sources is however needed to unravel the involvement of DNA double strand break repair pathways and proteins in the cellular response of human cells to high-LET radiation.