Hip synovial cyst presenting as femoral hernia - case report.

We are pleased to introduce this interesting case report. A female patient presented to emergency department with a new lump in her right groin. Although there was quite convincing history for femoral hernia, the clinical findings were not correlating with this completely. The patient underwent ultrasound examination which showed synovial cyst originating from the right hip. This is a rare presentation of hip synovial cyst and we have therefore decided to publish this case report.

Small molecule inhibitors of DNA-PK for tumor sensitization to anticancer therapy.

The most sensitive cell structure - a DNA molecule, is the common target of cancer therapy. DNA damage response (controlled by enzymes from the phosphatidylinositol 3-kinase-related kinases family - PIKK) presents many encouraging targets for improving both conventional cytotoxic anticancer therapy and individualized monotherapy. DNA-dependent protein kinase (DNA-PK) is a member of the PIKK superfamily and plays an important role in the detection and repair of DNA double-strand breaks via the non-homologous end-joining pathway. The ability of cancer cells to repair DNA damage is an important element determining their sensitivity to radio- or chemo-therapy. The overactivation of DNA-PK in cancers can result in resistance to anticancer therapy. The inhibition of DNA-PK is a very promising target in anticancer research. However, the specific DNA-PK inhibitors currently known are limited by poor solubility and high metabolic lability in vivo, leading to a short serum half-life. Construction of new compounds based on existing drugs is the most important strategy to improve drug efficacy, pharmacokinetic parameters and to reduce toxicity. This review will describe small molecule inhibitors and summarize their efficacy in synergizing radio- and chemotherapy in vitro.

Comparison of the Radiosensitizing Effect of ATR, ATM and DNA-PK Kinase Inhibitors on Cervical Carcinoma Cells.

Here, we compared the effects of inhibitors of three phosphatidylinositol-3-kinase-related kinases, ATM, ATR a DNA-PK, on radiosensitization of cervical carcinoma cells. We demonstrated that DNA-PK inhibitor NU7441 enhanced phosphorylation of Chk1 and Chk2 kinases 2 h after irradiation of HeLa cells at a dose of 8 Gy in contrast to ATM kinase inhibitor KU55933, which completely blocked the Chk2 kinase phosphorylation on threonine 68, and ATR kinase inhibitor VE-821, which blocked the Chk1 kinase phosphorylation on serine 345. Most HeLa cells were accumulated in G2 phase of the cell cycle 24 h after irradiation at a high dose of 15 Gy, which was even potentiated after adding the inhibitors NU7441 and KU55933. Compared to all other irradiated groups, inhibitor VE-821 increased the number of cells in S phase and reduced the number of cells in G2 phase 24 h after irradiation at the high dose of 15 Gy. HeLa cells entered the mitotic cycle with unrepaired DNA, which resulted in cell death and the radiosensitizing effect of VE-821. Short-term application of the inhibitors (2 h before and 30 min after the irradiation by the dose of 8 Gy) significantly decreased the colony-forming ability of HeLa cells. Using real-time monitoring of cell proliferation by the xCELLigence system we demonstrated that while the radiosensitizing effect of VE-821 (ATR inhibitor) is manifested early after the irradiation, the radiosensitizing effect of KU55933 (ATM inhibitor) and NU7441 (DNA-PK inhibitor) is only observed as late as 72 h after the irradiation.

The role of cytokines TGF-beta1 and FGF-1 in the expression of characteristic markers of rat liver myofibroblasts cultured in three-dimensional collagen gel.

Rat liver myofibroblasts (MFB) are the key cells involved in the deposition of extracellular matrix in fibrotic liver. They were isolated by repeated passaging of non-parenchymal cell fraction and cultured in 3-dimensional (3D) collagen gel mimicking tissue. The transfer of MFB from plastic dishes to collagen resulted in the change in their shape from large and spread to slender with long extensions. The expression of transforming growth factor-beta1 (TGF-beta1) and of MFB markers, alpha-smooth muscle actin (alpha-SMA) and cellular fibronectin (EDA-FN), on protein level was significantly decreased in collagen gel. The gel did not change the expression of metalloproteinase MMP-2 but activated the proenzyme. The experiments with inhibitors of metabolic pathways showed that EDA-FN and alpha-SMA were differently regulated. The expression of EDA-FN required functional TGF-beta1 receptors and was also dependent on the activity of protein kinases MEK1 and MEK2. alpha-SMA expression was primarily determined by the 3D environment. Fibroblast growth factor-1 (FGF-1) in combination with heparin decreased the expression of alpha-SMA and increased the expression of EDA-FN in the cells on plastic. The cellular environment may influence the cells per se and may modify the action of other agents.

Benfluron Induces Cell Cycle Arrest, Apoptosis and Activation of p53 Pathway in MOLT-4 Leukemic Cells.

The aim of our study was to determine the effect of potential anti-tumour agent benfluron on human leukemic cells MOLT-4 and elucidate the molecular mechanisms of response of tumour cells to this chemotherapeutic agent. It has been shown that the mechanisms of action of benfluron are complex, but the molecular pathways of the cytostatic effect have remained unknown and the present study contributes to their elucidation. In this work, benfluron reduced viability of the treated cells and induced caspase-mediated apoptosis. The programmed cell death was associated with activation of caspases 8, 9 and 3/7. Moreover, exposure of cells to benfluron resulted in accumulation of the cells primarily in late S and G2/M phases. The changes in the levels of key proteins show that benfluron provoked activation of p53 and induced phosphorylation of p53 on serine 15 and serine 392. The application of benfluron led to phosphorylation of Chk1 on serine 345 and phosphorylation of Chk2 on threonine 68 in the treated cells. Higher doses of benfluron caused phosphorylation of ERK1/2 on threonine 202 and tyrosine 204, whereas JNK and p38 kinases were not activated. In conclusion, benfluron induces apoptosis, cell cycle arrest in late S and G2/M phases, and activates various signalling pathways of the DNA damage response.

Subcellular Localization of Proteins Responding to Mitoxantrone-Induced DNA Damage in Leukaemic Cells.

The aim of the present study was to investigate the subcellular localization of proteins participating in the double-strand break response pathway - p53, Mdm2, p21 and Chk2. MOLT-4 cells were pre-treated with mitoxantrone in concentrations 1 nmol/l and 5 nmol/l. The trypan blue technique was used to determine cell viability and proliferation. Western blotting was used to evaluate changes in p53, Mdm2 and Chk2 protein expression and sandwich ELISA was used to evaluate changes in the p21 protein amount. After 1 nmol/l mitoxantrone cells did not die, but their ability to proliferate was decreased. The p53 protein was activated and phosphorylated at serines 15 and 392 and accumulated in the nucleus after 24 and 48 h. The Mdm2 protein was present in the cytoplasm with its maximal level after 8 and 16 h. The p21 protein was detected in the nucleus after 24 and 48 h. Increased levels of phosphorylated Chk2 at threonine 68 were observed in the cytoplasmic fraction after 24 and 48 h of mitoxantrone treatment. We used mitoxantrone as an inducer of double-strand breaks to bring new data about the subcellular distribution of proteins responding to DNA damage. In MOLT-4 cells, the p53 protein was activated. p53 was phosphorylated at serines 15 and 392 and accumulated in the nucleus. The Mdm2 protein was activated in advance to p53 and occurred in the cytoplasm. The p21 protein was present in the nucleus. Chk2 kinase was activated by the phosphorylation at threonine 68 and we observed increased levels of this protein in the cytoplasmic fraction.

Importance of proapoptotic protein PUMA in cell radioresistance.

Protein p53 plays an essential role in the induction of apoptosis by ionizing radiation in haemopoietic cells, the damage of which is the main reason for the development of bone marrow post-irradiation syndrome. p53 activation leads to an increase in the Bcl-2 family pro-apoptotic protein PUMA level. PUMA inhibits all the five anti-apoptotic proteins (Mcl-1, Bcl-2, Bcl-XL, Bcl-W and A1) and directly triggers apoptosis mediated by pro-apoptotic proteins Bax/Bak. In proliferating cells, knockout of p53 inhibits apoptosis on the one hand, but on the other disables the cellular division arrest moderated by p21Cip1/Waf1. The radioprotective effect of p53 inhibitor pifithrin was obvious at radiation doses causing the bone marrow syndrome. Knockout of PUMA also exerts its radioprotective effect through blocking the apoptosis induction, but the arrest of cells in the cell cycle through p21 induction is not abolished. PUMA -/- mice are radioresistant in terms of the development of post-irradiation syndrome after all radiation doses. Small molecules are being searched for that could prevent binding of PUMA with Bcl-2 family anti-apoptotic proteins. This would result in apoptosis inhibition and radioprotective or mitigating effects of these inhibitors.

Ionizing radiation induces senescence and differentiation of human dental pulp stem cells.

Head and neck cancer is one of the most common cancers in Europe. Many current anti-cancer treatments, including ionizing radiation, induce apoptosis via DNA damage. Unfortunately, such treatments are non-selective to cancer cells and produce similar toxicity in normal cells, including adult stem cells. One of the fundamental properties of an adult stem cell is that it does not have any tissue-specific structures that allow it to perform specialized functions. However, under certain stimuli, unspecialized adult stem cells can give rise to specialized cells to generate replacements for cells that are lost during one's life or due to injury or disease. Nevertheless, specialization of stem cells must be controlled by specific milieu and also initiated at the proper time, making the entire process beneficial for tissue recovery and maintaining it for a long time. In this paper we assess whether irradiated dental pulp stem cells have maintained open their options to mature into specialized cells, or whether they have lost their unspecialized (immature) state following irradiation. Our findings showed radiation-induced premature differentiation of dental pulp stem cells towards odonto-/osteoblast lineages in vitro. Matrix calcification was visualized from Day 6 or Day 9 following irradiation of cells expressing low or high levels of CD146, respectively.

In vivo study of radioprotective effect of NO-synthase inhibitors and acetyl-L-carnitine.

This study investigated the protective effect of two nitric oxide synthase inhibitors N(omega)-nitro-L-arginine methyl ester (L-NAME, 100 mg/kg i.p.) and aminoguanidine (AG, 400 mg/kg i.p.), and an antioxidant acetyl-L-carnitine (ALC, 250 mg/kg i.p., once daily for five days) against radiation-induced damage in Wistar rats. Blood samples were collected 6 h after whole-body irradiation with 8 Gy. Plasma concentrations of nitrite+nitrate (NO(x)) and malondialdehyde (MDA) were measured by high-performance liquid chromatography. A single injection of L-NAME one hour before exposure effectively prevented the radiation-induced elevation of plasma NO(x) and it reduced 2.6-fold the risk for death during the subsequent 30-day period. Pretreatment with ALC prevented the radiation-induced increase in plasma MDA and it had similar effect on mortality as L-NAME did. Presumably due to its short half-life, the partially iNOS-selective inhibitor and antioxidant AG given in a single dose before exposure did not attenuate MDA and NO(x) and it failed to significantly improve the 30-day survival. In conclusion, pretreatment with both the nonspecific NOS inhibitor L-NAME and the antioxidant ALC markedly reduce mortality to radiation sickness in rats. The radioprotective effect may be directly related to effective attenuation of the radiation-induced elevation of NO production by L-NAME and of oxidative stress by ALC.

Mitoxantrone ability to induce premature senescence in human dental pulp stem cells and human dermal fibroblasts.

UNLABELLED: In this study we assessed the effects of the frequently used chemotherapeutic agent mitoxantrone (MTX) on dental pulp stem cells (DPSCs) and compared it with the response of human dermal fibroblasts (HDFs). DPSCs are valuable source of mesenchymal stem cells which may be extremely useful in a number of clinical applications. It is evident that both normal and tumor cells are being affected during therapy and characterization of these cells under genotoxic stress contributes to the evaluation of their safety usage. In the experiment cells were exposed to doses 5-150 nmol/l MTX. Proliferation of cells was detected by Z2 counter and viability by Vi-Cell XR using Trypan blue exclusion staining. Cell cycle analysis was determinated by flow cytometry, induction of apoptosis by monitoring the activities of caspases. The expression of key proteins was detected by Western blotting. Senescence was analyzed by activity of ß-galactosidase and by detection of persisting DSBs-associated γH2AX foci. Exposure of both cell types to lower concentrations of MTX resulted in premature senescence (SIPS), which was accompanied with typical morphological changes, increased activity of senescence-associated ß-galactosidase, persisting DSBs-associated γH2AX foci and cell cycle arrest in G2 phase. MTX provokes the activation of p53-p21(WAF1/Cip1) pathway in both cell types and activates cell-cycle inhibitor p16(INK4a) in HDFs, but not in DPSCs. Higher concentrations of MTX induced caspase-mediated apoptosis. CONCLUSIONS: MTX induces apoptosis or SIPS in both cell types in dependency on MTX doses. Both pathways prevent the proliferation of cells with damaged DNA.

Collagenolytic potential of rat liver myofibroblasts.

Rat liver myofibroblasts (MFB) were isolated by repeated passaging of nonparenchymal liver cell fraction. They were cultured on polystyrene Petri dishes, on fibrin or on type I collagen gels for 5 days. Quantitative RT-PCR, Western blotting, zymography and immunocytochemistry were used to study differences in cell morphology and protein expression. MFB were large and spread on plastic substrate, with prominent alpha-smooth muscle (alpha-SMA) fibres. They turned much smaller and elongated on collagen which was accompanied by the rearrangement of the cytoskeleton and a decrease in alpha-SMA and beta-actin content. Collagen gel induced the expression of a group of metalloproteinases (MMP-2, -3, -9, -13), on mRNA and protein level which resulted in the degradation of the gel. This response was accompanied by changes in the mRNA expression of cytokines of TGF-beta family, CTGF and interleukin-6, as well as of osteopontin and thrombospondin-2 that are involved in metalloproteinases (MMPs) regulation. The expression of MMPs substrates, collagen types I, IV and XII did not change or decreased. The effects of fibrin gels on MFB were milder than those of collagen. MFB assumed to deposit collagen and other ECM components in fibrotic liver, besides hepatic stellate cells, also possess a great collagenolytic potential.

Valproic acid decreases the reparation capacity of irradiated MOLT-4 cells.

The aim of our work was to evaluate mechanisms leading to radiosensitization of MOLT-4 leukemia cells following valproic acid (VA) treatment. Cells were pretreated with 2 mM VA for 24 h followed by irradiation with a dose of 0.5 or 1 Gy. The effect of both noxae, alone and combined, was detected 1 and 24 hours after the irradiation. Induction of apoptosis was evaluated by a flow cytometry. The extent of DNA damage was further determined by phosphorylation of histone H2AX using confocal microscopy. Changes in protein expression were identified by SDS-PAGE/immunoblotting. Two-millimolar VA increased apoptosis induction after irradiation as well as phosphorylation of H2AX and provokes an increase in the level of p53 and its phosphorylation at Ser392 in 4 h post-irradiation. Likewise, p21 protein reached its maximal expression in 4 h after the irradiation of VA-treated cells. Twenty four hours later, only the p53 phosphorylated at Ser15 was detected. At the same time, the protein mdm2 (negative regulator of p53) was maximally activated. The 24-hour treatment of MOLT-4 leukemia cells with 2 mM VA results in radiosensitizing, increases apoptosis induction, H2AX phosphorylation, and also p53 and p21 activation.

The response of human ectomesenchymal dental pulp stem cells to cisplatin treatment.

AIM: To determine the response of dental pulp stem cells (DPSCs) to DNA-damaging cytostatic cisplatin and compare it with the response of normal human dermal fibroblasts (HDFs). METHODOLOGY: Dental pulp stem cells were exposed to 5, 10, 20 or 40 µmol L(-1) of cisplatin. The proliferation of affected cells was assessed by a Z2 Counter and viability was assessed by means of a Vi-Cell XR using Trypan blue exclusion staining. Cell cycle analysis and induction of apoptosis were performed by flow cytometry. Induction of apoptosis was determined by monitoring the activities of caspases. The expression of proteins was detected by electrophoresis and Western blotting. The descriptive statistics of the results was analyzed by Student's t-test. RESULTS: Dental pulp stem cells had a greater genotoxic stress response to cisplatin compared to HDFs. All three main Mitogen-activated protein kinases (MAPK) families - extracellular signal-regulated kinases (ERK), c-Jun-N-terminal kinase (JNK) and p38 were activated after treatment of DPSCs with cisplatin. The activation of MAPK pathways was not observed in HDFs exposed to cisplatin. The exposure of DPSCs and HDFs to cisplatin provoked an increase in p53 and p21 expression and p53 phosphorylation of serine 15. Higher concentrations of cisplatin reduced the viability of DPSCs and HDFs and induced the activation of caspases 3/7 and 9. CONCLUSION: Dental pulp stem cells had a greater genotoxic stress response to cisplatin compared to HDFs. Cisplatin in higher concentrations triggered activation of MAPK and apoptosis in DPSCs but not in HDFs.

Mitoxantrone in combination with a DNA-PK inhibitor: possible therapy of promyelocytic leukaemia resistant forms.

The aim of the study was to sensitize cells of human promyelocytic leukaemia HL-60/MX2 (resistant to mitoxantrone and further substances interacting with topoisomerase II) to the effect of mitoxantrone (MTX). We demonstrated that the main mechanism of the HL-60/MX2 cell atypical multiple drug resistance is not only their altered activity of topoisomerase II and reduced levels of topoisomerase II α and ß proteins. The resistance of the HL-60/ MX2 cells to MTX is associated with their increased ability to repair DNA double-strand breaks (DSBs) in these cells. The HL-60/MX2 cells, compared to HL-60 cells (which are sensitive to MTX effects), contain large amounts of DNA-PK, which is responsible for the main pathway of the DSB repair, nonhomogenous end joining (NHEJ), and they also contain large amounts of further repair proteins Rad50 and Nbs1, which are important in both types of the repair processes (NHEJ as well as homologous recombination). We demonstrated that specific DNAPK inhibitor NU7026 reduced the amount of DNAPK in HL60/MX2, thus preventing the DSB repair through the NHEJ pathway after the incubation with MTX and in this way essentially abolished the resistance of these cells to MTX.

p21Cip1/Waf1 protein and its function based on a subcellular localization [corrected].

Protein p21(Cip1/Waf1) is a cyclin-dependent kinase inhibitor, which is important in the response of cells to genotoxic stress and a major transcriptional target of p53 protein. Based on the localization, p21(Cip1/Waf1) protein executes various functions in the cell. In the nucleus p21(Cip1/Waf1) binds to and inhibits the activity of cyclin dependent kinases Cdk1 and Cdk2 and blocks the transition from G1 phase into S phase or from G2 phase into mitosis after DNA damage. This enables the repair of damaged DNA. p21(Cip1/Waf1) was also found as an important protein for the induction of replication senescence as well as stress-induced premature senescence. In the cytoplasm, p21(Cip1/Waf1) protein has an anti-apoptotic effect. It is able to bind to and inhibit caspase 3, as well as the apoptotic kinases ASK1 and JNK. The function of p21(Cip1/Waf1) in response to a DNA damage probably depends on the extent of the damage. In the case of low-level DNA damage, the expression of p21(Cip1/Waf1) is increased, it induces cell cycle arrest, and performs also anti-apoptotic activities. However, after extensive DNA damage the amount of p21(Cip1/Waf1) protein is decreased and the cell undergoes apoptosis. Dual function of p21(Cip1/Waf1) was also observed in cancerogenesis. On the one hand, p21(Cip1/Waf1) acts as a tumor suppressor; on the other hand it prevents apoptosis and acts as an oncogene. Better understanding of the role of p21(Cip1/Waf1) in various conditions would help to develop better cancer-treatment strategies.

The importance of senescence in ionizing radiation-induced tumour suppression.

Cellular senescence is a condition of longlasting proliferation arrest, induced in cells in response to various stressors. These stressors include telomere shortening and/or dysfunction, DNA damage, and oncogene signalling. Epithelial and mesenchymal cells and also tumour cells derived from these tissues are more resistant to radiation-induced apoptosis and respond to irradiation mainly by senescence. Senescence-associated molecular mechanisms related to the activation of canonical DNA damage pathway ATM-p53 as well as mechanisms related to the extracellular signals, cytokine increase and upregulation of their receptors are discussed in this review.

The effect of ATM and ERK1/2 inhibition on mitoxantrone-induced cell death of leukaemic cells.

The relationship between signal pathways MEK1/2-ERK1/2 and ATM-p53 in the response to DNA damage is not well understood. The aim of our study was to investigate the effect of mitoxantrone and two protein kinase inhibitors - caffeine (inhibitor of ATM kinase) and U0126 (inhibitor of MEK1/2 kinase) - on MOLT-4 and Jurkat leukaemic cell lines. In this work we show that the inhibition of MEK1/2 is associated with an increased mortality of cells after mitoxantrone treatment. Inhibition of ATM by caffeine delayed mitoxantrone-induced cell death in MOLT-4 cells. Mitoxantrone itself induced cell-cycle arrest and accumulation of the cells in late S and G2/M phase. Inhibition of ATM, but not of MEK1/2, abrogated mitoxantrone-induced cell-cycle arrest. Inhibition of MEK1/2 did not change mitoxantroneinduced up-regulation of p53 and p21, but inhibition of ATM markedly decreased up-regulation of p53 and p21, and p53 phosphorylation on serine 15 and serine 392. It can be concluded that: 1) mitoxantrone- induced phosphorylation of p53 on serine 15 and serine 392 is ATM dependent and MEK1/2-ERK1/2 independent. 2) ATM inhibition by caffeine prevents G2 cell arrest and in p53-positive cells MOLT-4 delays the onset of mitoxantrone-induced cell death. 3) Inhibition of MEK1/2-ERK1/2 cascade potentiates the cytostatic effect of mitoxantrone regardless of the p53 status.

DNA damage caused by ionizing radiation in embryonic diploid fibroblasts WI-38 induces both apoptosis and senescence.

Cellular response to ionizing radiation-induced damage depends on the cell type and the ability to repair DNA damage. Some types of cells undergo apoptosis, whereas others induce a permanent cell cycle arrest and do not proliferate. Our study demonstrates two types of response of embryonic diploid fibroblasts WI-38 to ionizing radiation. In the WI-38 cells p53 is activated, protein p21 increases, but the cells are arrested in G2 phase of cell cycle. Some of the cells die by apoptosis, but in remaining viable cells p16 increases, senescence associated DNA-damage foci occur, and senescence-associated beta-galactosidase activity increases, which indicate stress-induced premature senescence.

Biochemical and pharmacological effects of mitoxantrone and acetyl-L-carnitine in mice with a solid form of Ehrlich tumour.

BACKGROUND: Dysfunction of the carnitine system in non-tumour tissue following anticancer therapy has been reported. In this setting, supplementation with carnitine derivatives might increase the general metabolic activity of normal cells so that they might better withstand the adverse effects of chemotherapy aimed at tumour cells. Here we investigated the effect of acetyl-L-carnitine (ALC) alone and in combination with the antineoplastic agent mitoxantrone (MX) in an animal cancer model. METHODS: The effects of MX and MX-ALC were assessed based on gain or loss of body weight and on local growth of a solid form of Ehrlich tumour inoculated into mice. We also performed biochemical analyses like serum activities of some enzymes signalling the functioning of the liver, aspartate aminotransferase (AST), and alanine aminotransferase (ALT). Total protein, albumin and bilirubin were also determined in serum. Under favourable conditions, the Ehrlich tumour readily forms metastases, and this is the reason why we performed histological studies of samples of both the liver and heart in order to identify changes that may have mediated the observed effect of the treatment. In addition to those studies, the survival time of treated animals against controls was also noted. RESULTS: MX monotherapy was associated with lower body weight gain, fewer metastases, smaller tumour size, and lower dissemination. ALC alone promoted survival, but had no potentiating effect on MX therapy in terms of survival. Serum biochemistry changes associated with MX-ALC treatment consisted of a significant (p < 0.05) increase in AST with MX at 6 or 9 mg·kg(-1) plus ALC 200 mg·kg(-1) and a significant (p < 0.05) reduction in total protein compared to the corresponding MX group; serum albumin and bilirubin remained unchanged. CONCLUSION: ALC in combination with MX, regardless of the dose of MX, led to higher occurrences of metastases with dissemination to the kidneys, lungs, heart, and mediastinum compared to MX treatment alone. These histological findings indicate that ALC is inappropriate to combine with MX in the treatment of a solid cancer. The protective effect of ALC in combination therapy with the cytostatic drug MX was not supported in this study by our findings that the agent did not improve the therapeutic outcomes of MX therapy.

Gamma-radiation-induced phosphorylation of p53 on serine 15 is dose-dependent in MOLT-4 leukaemia cells.

Molecular indicators of the absorbed dose of ionizing radiation are powerful tools in biodosimetry. The studies reported here were undertaken with the motivation to find such a marker among the mo lecules involved in ataxia-telangiectasia mutated kinase- dependent signalling induced by ionizing radiation (ATM-kinase, checkpoint kinase-2, protein p53, and oncoprotein Mdm2). In our previous work on T-lymphocyte leukaemia MOLT-4 cells we described the mentioned molecules of ATM-dependent pathway and none of them showed a pronounced dosedependent response. Here we employed Western blotting and ELISA assay to investigate the response of post-translationally modified p53 (particularly phosphorylated on serine 15) after gamma-irradiation. We have found the amount of phosphorylated p53 to be homogenously increased after irradiation by the doses of 0.5 to 7.5 Gy. The dose-dependent response was pronounced especially after the doses up to 3.0 Gy. The presented data indicate that p53 phosphorylated on serine 15 might be used as a potential biodosimetric marker.