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Mannan-binding lectin-associated serine protease 1 (MASP-1), the most abundant enzyme of the complement lectin pathway, is able to stimulate human umbilical vein endothelial cells (HUVECs) to alter the expression of several cytokines and adhesion molecules. This study has assessed to what extent MASP-1 is able to modify the transcriptional pattern of inflammation-related (IR) genes in HUVECs. We utilized Agilent microarray to analyse the effects of recombinant MASP-1 (rMASP-1) in HUVECs, on a set of 884 IR genes. Gene Set Enrichment Analysis showed an overall activation of inflammation-related genes in response to rMASP-1. rMASP-1 treatment up- and down-regulated 19 and 11 IR genes, respectively. Most of them were previously unidentified, such as genes of chemokines (CXCL1, CXCL2, CXCL3), inflammatory receptors (TLR2, BDKRB2) and other inflammatory factors (F3, LBP). Expression of IR genes changed early, during the first 2 hours of activation. Both p38-MAPK inhibitor and NFκB inhibitor efficiently suppressed the effect of rMASP-1. We delineated 12 transcriptional factors as possible regulators of rMASP-1-induced IR genes. Our microarray-based data are in line with the hypothesis that complement lectin pathway activation, generating active MASP-1, directly regulates inflammatory processes by shifting the phenotype of endothelial cells towards a more pro-inflammatory type.

The complement system and neutrophil granulocytes are indispensable in the immune response against extracellular pathogens such as bacteria and fungi. Endothelial cells also participate in antimicrobial immunity largely by regulating the homing of leukocytes through their cytokine production and their pattern of cell surface adhesion molecules. We have previously shown that mannan-binding lectin-associated serine protease-1 (MASP-1), a complement lectin pathway enzyme, is able to activate endothelial cells by cleaving protease activated receptors, which leads to cytokine production and enables neutrophil chemotaxis. Therefore, we aimed to investigate how recombinant MASP-1 (rMASP-1) can modify the pattern of P-selectin, E-selectin, ICAM-1, ICAM-2, and VCAM-1 adhesion molecules in human umbilical vein endothelial cells (HUVEC), and whether these changes can enhance the adherence between endothelial cells and neutrophil granulocyte model cells (differentiated PLB-985). We found that HUVECs activated by rMASP-1 decreased the expression of ICAM-2 and increased that of E-selectin, whereas ICAM-1, VCAM-1 and P-selectin expression remained unchanged. Furthermore, these changes resulted in increased adherence between differentiated PLB-985 cells and endothelial cells. Our finding suggests that complement MASP-1 can increase adhesion between neutrophils and endothelial cells in a direct fashion. This is in agreement with our previous finding that MASP-1 increases the production of pro-inflammatory cytokines (such as IL-6 and IL-8) and chemotaxis, and may thereby boost neutrophil functions. This newly described cooperation between complement lectin pathway and neutrophils via endothelial cells may be an effective tool to enhance the antimicrobial immune response.

Background and purpose The reliable assessment of proarrhythmic risk of compounds under development remains an elusive goal. Current safety guidelines focus on the effects of blocking the KCNH2/HERG ion channel-in tissues and animals with intact repolarization. Novel models with better predictive value are needed that more closely reflect the conditions in patients with cardiac remodelling and reduced repolarization reserve. Experimental approach We have developed a model for the long QT syndrome type-5 in rabbits (LQT5 ) with cardiac-specific overexpression of a mutant (G52R) KCNE1 β-subunit of the channel that carries the slow delayed-rectifier K(+) -current (IKs ). ECG parameters, including short-term variability of the QT interval (STVQT ), a biomarker for proarrhythmic risk, and arrhythmia development were recorded. In vivo, arrhythmia susceptibility was evaluated by i.v. administration of the IKr blocker dofetilide. K(+) currents were measured with the patch-clamp technique. Key results Patch-clamp studies in ventricular myocytes isolated from LQT5 rabbits revealed accelerated IKs and IKr deactivation kinetics. At baseline, LQT5 animals exhibited slightly but significantly prolonged heart-rate corrected QT index (QTi) and increased STVQT . Dofetilide provoked Torsade-de-Pointes arrhythmia in a greater proportion of LQT5 rabbits, paralleled by a further increase in STVQT . Conclusion and implications We have created a novel transgenic LQT5 rabbit model with increased susceptibility to drug-induced arrhythmias that may represent a useful model for testing proarrhythmic potential and for investigations of the mechanisms underlying arrhythmias and sudden cardiac death due to repolarization disturbances.

Pathologically increased vascular permeability is an important dysfunction in the pathomechanism of life-threatening conditions, such as sepsis, ischemia/reperfusion, or hereditary angioedema (HAE), diseases accompanied by uncontrolled activation of the complement system. HAE for example is caused by the deficiency of C1-inhibitor (the main regulator of early complement activation), which leads to edematous attacks threatening with circulatory collapse. We have previously reported that endothelial cells become activated during HAE attacks. A natural target of C1-inhibitor is mannan-binding lectin-associated serine protease-1 (MASP-1), a multifunctional serine protease, which plays a key role in the activation of complement lectin pathway. We have previously shown that MASP-1 induces the pro-inflammatory activation of endothelial cells and in this study we investigated whether MASP-1 can directly affect endothelial permeability. All experiments were performed on human umbilical vein endothelial cells (HUVECs). Real-time micro electric sensing revealed that MASP-1 decreases the impedance of HUVEC monolayers and in a recently developed permeability test (XperT), MASP-1 dose-dependently increased endothelial paracellular transport. We show that protease activated receptor-1 mediated intracellular Ca2+-mobilization, Rho-kinase activation dependent myosin light chain (MLC) phosphorylation, cytoskeletal actin rearrangement, and disruption of interendothelial junctions are underlying this phenomenon. Furthermore, in a whole-transcriptome microarray analysis MASP-1 significantly changed the expression of 25 permeability-related genes in HUVECs—for example it up-regulated bradykinin B2 receptor expression. According to our results, MASP-1 has potent permeability increasing effects. During infections or injuries MASP-1 may help eliminate the microbes and/or tissue debris by enhancing the extravasation of soluble and cellular components of the immune system, however, it may also play a role in the pathomechanism of diseases, where edema formation and complement lectin pathway activation are simultaneously present. Our findings also raise the possibility that MASP-1 may be a promising target of anti-edema drug development.

AIMS Short-QT syndrome 1 (SQT1) is an inherited channelopathy with accelerated repolarization due to gain-of-function in HERG/IKr. Patients develop atrial fibrillation, ventricular tachycardia (VT), and sudden cardiac death with pronounced inter-individual variability in phenotype. We generated and characterized transgenic SQT1 rabbits and investigated electrical remodelling. METHODS AND RESULTS Transgenic rabbits were generated by oocyte-microinjection of β-myosin-heavy-chain-promoter-KCNH2/HERG-N588K constructs. Short-QT syndrome 1 and wild type (WT) littermates were subjected to in vivo ECG, electrophysiological studies, magnetic resonance imaging, and ex vivo action potential (AP) measurements. Electrical remodelling was assessed using patch clamp, real-time PCR, and western blot. We generated three SQT1 founders. QT interval was shorter and QT/RR slope was shallower in SQT1 than in WT (QT, 147.8 ± 2 ms vs. 166.4 ± 3, P

There is a difficulty in the molecular diagnosis of congenital adrenal hyperplasia (CAH) due to the c.955C>T (p.(Q319*), formerly Q318X, rs7755898) variant of the CYP21A2 gene. Therefore, a systematic assessment of the genetic and evolutionary relationships between c.955C>T, CYP21A2 haplotypes and the RCCX copy number variation (CNV) structures, which harbor CYP21A2, was performed. In total, 389 unrelated Hungarian individuals with European ancestry (164 healthy subjects, 125 patients with non-functioning adrenal incidentaloma and 100 patients with classical CAH) as well as 34 adrenocortical tumor specimens were studied using a set of experimental and bioinformatic methods. A unique, moderately frequent (2%) haplotypic RCCX CNV structure with three repeated segments, abbreviated to LBSASB, harboring a CYP21A2 with a c.955C>T variant in the 3'-segment, and a second CYP21A2 with a specific c.*12C>T (rs150697472) variant in the middle segment occurred in all c.955C>T carriers with normal steroid levels. The second CYP21A2 was free of CAH-causing mutations and produced mRNA in the adrenal gland, confirming its functionality and ability to rescue the carriers from CAH. Neither LBSASB nor c.*12C>T occurred in classical CAH patients. However, CAH-causing CYP21A2 haplotypes with c.955C>T could be derived from the 3'-segment of LBSASB after the loss of functional CYP21A2 from the middle segment. The c.*12C>T indicated a functional CYP21A2 and could distinguish between non-pathogenic and pathogenic genomic contexts of the c.955C>T variant in the studied European population. Therefore, c.*12C>T may be suitable as a marker to avoid this genetic confound and improve the diagnosis of CAH.

Among the many functions of the neonatal Fc receptor (FcRn) for IgG, it binds to IgG-opsonized antigen complexes and propagates their traffic into lysosomes where antigen processing occurs. We previously reported that transgenic (Tg) mice and rabbits that carry multiple copies and overexpress FcRn have augmented humoral immune responses. Nuclear factor-kappa B (NFκB) is a critical molecule in the signaling cascade in the immune response. NFκB induces human FcRn expression and our previous in silico analysis suggested NFκB binding sites in the promoter region of the bovine (b) FcRn α-chain gene (FCGRT). Here, we report the identification of three NFκB transcription binding sites in the promoter region of this gene using luciferase reporter gene technology, electromobility shift assay and supershift analysis. Stimulation of primary bovine endothelial cells with the Toll-like receptor-4 ligand lipopolysaccharide (LPS), which mediates its effect via NFκB, resulted in rapid upregulation of the bFcRn expression and a control gene, bovine E-selectin. This rapid bFcRn gene induction was also observed in the spleen of bFcRn Tg mice treated with intraperitoneally injected LPS, analyzed by northern blot analysis. Finally, NFκB-mediated bFcRn upregulation was confirmed at the protein level in macrophages isolated from the bFcRn Tg mice using flow cytometry with a newly developed FcRn specific monoclonal antibody that does not cross-react with the mouse FcRn. We conclude that NFκB regulates bFcRn expression and thus optimizes its functions, e.g., in the professional antigen presenting cells, and contributes to the much augmented humoral immune response in the bFcRn Tg mice.

Background Protein kinases are important components of signalling pathways, and kinomes have remarkably expanded in plants. Yet, our knowledge of kinase substrates in plants is scarce, partly because tools to analyse protein phosphorylation dynamically are limited. Here we describe Kinase-Associated Phosphoisoform Assay, a flexible experimental method for directed experiments to study specific kinase-substrate interactions in vivo. The concept is based on the differential phosphoisoform distribution of candidate substrates transiently expressed with or without co-expression of activated kinases. Phosphorylation status of epitope-tagged proteins is subsequently detected by high-resolution capillary isoelectric focusing coupled with nanofluidic immunoassay, which is capable of detecting subtle changes in isoform distribution. Results The concept is validated by showing phosphorylation of the known mitogen-activated protein kinase (MAPK) substrate, ACS6, by MPK6. Next, we demonstrate that two transcription factors, WUS and AP2, both of which are shown to be master regulators of plant development by extensive genetic studies, exist in multiple isoforms in plant cells and are phosphorylated by activated MAPKs. Conclusion As plant development flexibly responds to environmental conditions, phosphorylation of developmental regulators by environmentally-activated kinases may participate in linking external cues to developmental regulation. As a counterpart of advances in unbiased screening methods to identify potential protein kinase substrates, such as phosphoproteomics and computational predictions, our results expand the candidate-based experimental toolkit for kinase research and provide an alternative in vivo approach to existing in vitro methodologies. Electronic supplementary material The online version of this article (doi:10.1186/s12870-016-0894-1) contains supplementary material, which is available to authorized users.

The reliable assessment of proarrhythmic risk of compounds under development remains an elusive goal. Current safety guidelines focus on the effects of blocking the KCNH2/HERG ion channel-in tissues and animals with intact repolarization. Novel models with better predictive value are needed that more closely reflect the conditions in patients with cardiac remodelling and reduced repolarization reserve.We have developed a model for the long QT syndrome type-5 in rabbits (LQT5 ) with cardiac-specific overexpression of a mutant (G52R) KCNE1 β-subunit of the channel that carries the slow delayed-rectifier K(+) -current (IKs ). ECG parameters, including short-term variability of the QT interval (STVQT ), a biomarker for proarrhythmic risk, and arrhythmia development were recorded. In vivo, arrhythmia susceptibility was evaluated by i.v. administration of the IKr blocker dofetilide. K(+) currents were measured with the patch-clamp technique.Patch-clamp studies in ventricular myocytes isolated from LQT5 rabbits revealed accelerated IKs and IKr deactivation kinetics. At baseline, LQT5 animals exhibited slightly but significantly prolonged heart-rate corrected QT index (QTi) and increased STVQT . Dofetilide provoked Torsade-de-Pointes arrhythmia in a greater proportion of LQT5 rabbits, paralleled by a further increase in STVQT .We have created a novel transgenic LQT5 rabbit model with increased susceptibility to drug-induced arrhythmias that may represent a useful model for testing proarrhythmic potential and for investigations of the mechanisms underlying arrhythmias and sudden cardiac death due to repolarization disturbances.

The phosphatidylinositol-3-kinase/AKT (PI3K/AKT) pathway is commonly deregulated in breast cancer through several mechanisms, including PI3K catalytic subunit alpha (PIK3CA) mutations and loss of phosphatase and tensin homolog (PTEN). The hiperactivated PI3K/AKT signaling can be associated with endocrine or trastuzumab therapy resistance and underscore the impact of targeting the pathway. Our aim was to identify PIK3CA mutations and the mechanisms of PTEN loss and assess their therapeutic consequences in breast cancer patients. In addition, we aimed to identify further possible therapeutic targets associated with PTEN loss. Sixty-nine primary breast cancer samples (24 ER+/PR+/HER2-, 20 HER2+ (ER-/PR-/HER2+) and 25 triple-negative (TN) samples) were studied. We determined the PTEN mRNA levels, PTEN and PIK3CA mutations, PTEN allelic loss and promoter hypermethylation. mRNA expression patterns of PTEN knocked out and wild type MCF10A cell lines were compared using oligonucleotide microarray and their sensitivity to FGFR1 inhibitor PD166866 was tested. Elevated PI3K/AKT pathway activity was found in 68% of TN and about 45% of ER+/PR+ and HER2+ tumors. PTEN loss was dominant in TN and HER2+ tumors, while PTEN loss and PI3K activation were equally represented in ER+/PR+ cancers. The coexistence of PTEN loss and PI3K activation was typical of a portion of HER2+ tumors. The PTEN-deficient MCF10A cell line showed increased expression of certain members of the fibroblast growth factor 2 (FGF2)/FGFR1 pathway. We suppose that loss of PTEN enhances the autocrine FGF signaling promoting cell proliferation. FGF-2 and FGFR1 can be potential targets in PTEN deficient breast cancers.Vizsgálataink célja a foszfatidilinozitol-3-kináz/AKT (PI3K/AKT) növekedési jelátviteli útvonal genomikai paramétereinek összehasonlítása volt különbözõ emlõdaganat-típusokban. A PI3K/AKT jelátviteli útvonal gyakran mutat fokozott aktivitást emlõdaganatokban a PI3K-aktiváció vagy a proteinfoszfatáz és tenzin homológ (PTEN) inaktiválódása következményeként, így a szignálútban szereplõ gének aktiválása/inaktiválása meghatározó szerepet játszik a kemorezisztencia (tamoxifen, trastuzumab) kialakulásában is. Ezért célul tûztük ki a PTEN-vesztés mechanizmusainak és a PI3K katalitikus alegysége (PIK3CA) „forrópont”-mutációinak meghatározását, mivel ezek az adatok a terápiás érzékenység elõrejelzését teszik lehetõvé. Új terápiás célpontok meghatározására PTEN-deficiens MCF10A sejtvonalat használtunk. Vizsgálatainkban 69 primer emlõtumorban határoztuk meg a PTEN-mRNS-szintet, a PTEN- és PIK3CA-mutációkat, valamint a PTEN-allélvesztést és promoter-hipermetilációt. PTEN-hiányos és PTEN-t expresszáló izogenikus MCF10A emlõráksejtvonalak mRNS-expressziós mintázatát oligonukleotid microarray segítségével hasonlítottuk össze, PD166866 FGFR1-inhibitorral szembeni érzékenységüket citotoxicitási assay-vel vizsgáltuk. Eredményeink szerint a tripla-negatív (TN) daganatok mintegy 68%-ában, míg az ER+/PR+ és HER2+ tumorok 45%-ában következetett be a PI3K/AKT út fokozott aktivitása. A TN és HER2+ daganatokra a PTEN gén funkcióvesztése jellemzõ. Az ER+/PR+ daganatokban vagy a PTEN-inaktiváció, vagy a PI3K-aktiválódás figyelhetõ meg. A HER2+ daganatok egy csoportjában a PTEN-inaktiváció és a PI3K-aktiváció együttesen fordul elõ. A PTEN-hiányos MCF10A emlõráksejtvonalban fokozott expressziót mutattak a fibroblaszt növekedési faktor 2 (FGF2)/FGFR1 jelútvonal egyes tagjai. Feltételezzük, hogy a PTEN hiánya felerõsíti az autokrin FGF-szignalizációt, mely fokozza a sejtproliferációt. Az FGF2 és FGFR1 ígéretes terápiás célpont lehet a PTEN-negatív emlõdaganatokban.

The human steroid 21-hydroxylase gene (CYP21A2) participates in cortisol and aldosterone biosynthesis, and resides together with its paralogous (duplicated) pseudogene in a multiallelic copy number variation (CNV), called RCCX CNV. Concerted evolution caused by non-allelic gene conversion has been described in great ape CYP21 genes, and the same conversion activity is responsible for a serious genetic disorder of CYP21A2, congenital adrenal hyperplasia (CAH). In the current study, 33 CYP21A2 haplotype variants encoding 6 protein variants were determined from a European population. CYP21A2 was shown to be one of the most diverse human genes (HHe=0.949), but the diversity of intron 2 was greater still. Contrary to previous findings, the evolution of intron 2 did not follow concerted evolution, although the remaining part of the gene did. Fixed sites (different fixed alleles of sites in human CYP21 paralogues) significantly accumulated in intron 2, indicating that the excess of fixed sites was connected to the lack of effective non-allelic conversion and concerted evolution. Furthermore, positive selection was presumably focused on intron 2, and possibly associated with the previous genetic features. However, the positive selection detected by several neutrality tests was discerned along the whole gene. In addition, the clear signature of negative selection was observed in the coding sequence. The maintenance of the CYP21 enzyme function is critical, and could lead to negative selection, whereas the presumed gene regulation altering steroid hormone levels via intron 2 might help fast adaptation, which broadly characterizes the genes of human CNVs responding to the environment.

Activation of the complement system can induce and enhance inflammatory reaction. Mannose-binding lectin-associated serine protease-1 (MASP-1) is an abundant protease of the complement lectin pathway; however, its physiological function is unclear. In this study, we demonstrate for the first time that MASP-1 is able to activate Ca2+ signaling, NF-κB, and p38 MAPK pathways in cultured HUVECs. Activation was initiated by MASP-1 only; the related protease, MASP-2, had no such effect. The phenomenon was dependent on the proteolytic activity of MASP-1, suggesting modulation of endothelial cell function through a protease-activated receptor (PAR). Using synthetic peptide substrates representing the protease-sensitive regions of PARs, we were able to demonstrate that PAR4 is a target of MASP-1. The presence of functionally active PAR4 in HUVECs was demonstrated using PAR4 agonist peptide and mRNA quantification. Finally, we showed that the amount of membrane-bound intact PAR4 decreases after MASP-1 treatment. All of these results provide a novel link between the regulation of endothelial cell function and complement system activation, and they suggest that MASP-1-induced PAR4 activation could contribute to the development of the inflammatory reaction.

Lung resistance-related protein (LRP) was first detected in a non-P-glycoprotein-mediated multidrug-resistant lung cancer cell line and has been shown to be the major human vault protein. The aim of this study was to evaluate the expression of LRP in germ cell testicular tumors (GCT) and to determine the correlation between LRP expression and the clinical outcome of these tumors.Seventy cases of primary testicular tumors were investigated. LRP protein was detected by immunohistochemistry and Western blotting methods. LRP mRNA was determined with RT-PCR. Patients' clinical parameters and tumor response to treatment were recorded.With immunohistochemistry, LRP was detected in 29 (41%) out of 70 primary testicular tumors. Twenty-two (63%) out of 35 tumors expressed LRP mRNA and LRP protein on examination by RT-PCR and Western blotting, respectively. Pure teratomas showed significantly higher LRP expression compared to other types of GCTs (p=0.0418). No relationship was demonstrated between the LRP immunostaining and stage of disease (p=0.2263). A significantly higher proportion of patients with LRP-negative tumors achieved complete response than those with LRP-positive tumors (p=0.0155). Patients whose tumors showed expression of LRP had significantly shorter overall survival (p=0.0428) than LRP-negative patients.Immunohistochemistry is a reliable method to evaluate LRP expression in testicular germ cell tumors. A positive correlation was found between LRP immunostaining and pure teratomas. LRP expression was associated with an adverse clinical outcome and shorter overall survival. Our findings suggest that LRP has prognostic value in testicular germ cell tumors and can predict clinical outcome.

Germ cell testicular cancers are well-curable neoplasms, because total remission can be achieved in about 80% of the cases. However, 15-20% of the patients die due to drug resistance (DR). A number of mechanisms of the multidrug resistance phenotype are known, including MDR/P-glycoprotein (P-gp) and the so-called multidrug resistance associated protein (MRP). Lung Resistance Protein (LRP) is an ATP dependent membrane transporter protein associated with MDR. In our present work we studied the expression of LRP in testicular cancers. LRP expression was determined by immunohistochemistry (IH), Western blot (WB) and RT-PCR techniques. Clinical resistance was defined in accordance with the clinical oncologic rules. In 29 (41%) of 70 primary testicular tumours and in 22 (63%) of 35 cases, elevated LRP levels were established by IH and WB, respectively. In the latter 63%, the LRP mRNA levels were elevated as well. Six cases of the 15 seminomas and 23 cases of the nonseminomatous germ cell tumours (NSGCT) proved to be positive. No relationship was demonstrated between LRP expression and the stage of the disease. Despite the LRP positivity of 6 tumour samples, all of the seminomas proved sensitive. Of the 39 sensitive NSGCT, 27 cases were LRP-negative, whereas 11 tumour samples of 16 patients belonging to the resistant group proved LRP-positive (p=0.04). The authors concluded that the expression of LRP is responsible for clinical drug resistance in non-seminomatous testicular cancer patients.

OBJECTIVES: Characterization of breast cancers by various tumour markers which are appropriate for the identification of high risk groups. Markers related to the metastasis cascade and tumour recurrence have been investigated. MATERIALS AND METHODS: RT-PCR was used to determine the expression of cytokeratin 20 in the bone marrow and sentinel lymph node of breast cancer patients (n=45). The expression of HER2, Cadherin E, Cyclin D, Bcl2 and Bax has been evaluated by Western blot (n=744 invasive ductal carcinomas and 117 invasive lobular carcinomas, 124 recurrent breast cancers). Mutations of p53, APC and beta Catenin genes were detected by PCR-SSCP method. RESULTS: Expression of cytokeratin 20 was found in 30% of the bone marrow samples indicating the presence of micrometastasis. The level of Cyclin D, HER2 and Bcl2 is elevated four-fold in the recurrent breast cancers. The metastasis of invasive ductal carcinomas is accompained by high frequency of p53 mutations (24%) and APC mutations (18%). The invasive lobular carcinomas could be characterized with low frequency of p53 mutation (3%), low level of Cadherin E and high level of catenin beta. CONCLUSIONS: Identification of micrometastasis can promote the development of therapeutic strategy. Evaluation of HER2 level and determination of p53 mutations contribute to the identification of high risk patients. Our results suggest that the progression of invasive ductal carcinomas depends on the APC mutations, while metastasis of invasive lobular carcinomas depends on beta catenin mutations.

Radiation is known to induce DNA damage resulting in the onset of apoptosis. The apoptosis is modulated by p53, Bcl2 and Bax proteins. High level of wild type p53 is required for radiation induced apoptosis. The p53 status, therefore, may be a crucial determinant of radiosensitivity of tumor cells. Overexpression of Bcl2, however, inhibits apoptosis via hetero- and homodimeric interaction. Bax might function as a cell death effector molecule that is neutralized by Bcl2. The aim of the present study is to investigate the correlation between p53, Bcl2, Bax and c-myc levels and the clinical response of head and neck cancer patients to radiation. The base line and 30 GY gamma radiation induced values of p53, Bcl2, Bax and c-myc were estimated by Western blot in 40 biopsies of head and neck cancers. We found that the radiosensitivity of head and neck cancer patients depends on the ratio of p53, Bcl2 and Bax protein levels. High Bcl2 levels resulted in radioresistance of cancer patients. Overexpression of Bax and c-myc may ensure the radiosensitivity of head and neck cancer patients. Our studies indicate that prediction of radiation sensitivity of tumors could be based on the simultaneous evaluation of p53, Bax and Bcl2 levels.