Inhibition of c-MET reverses radiation-induced malignant potential in pancreatic cancer.

As a treatment option for PDAC, radiation therapy induces good local control. However, radiation also reportedly enhances the malignant potential (e.g., invasion and migration ability) in various cancers, thus increasing the risk of distant metastasis. It remains unclear how radiation induces malignant potential, and how such enhanced malignant potential can be suppressed. In the current study, we evaluated the sequential change of c-Met expression in pancreatic cancer cells following irradiation. We found that irradiation transiently induced c-Met expression in vitro. In an in vivo subcutaneous tumor mouse model, irradiation also enhanced downstream phosphorylated Met (p-Met). Furthermore, this enhancement of p-Met protein expression was suppressed by oral administration of the c-Met inhibitor INC280. Irradiated pancreatic cancer cells with enhanced c-Met expression exhibited higher malignant potential, including invasion and migration ability, compared with cells showing low c-Met expression. Pancreatic cancer cells that overexpressed c-met also showed enhanced malignant potential, which was reversed by c-Met inhibition. Additionally, c-Met inhibitor suppressed the metastatic potential in a liver metastasis mouse model using c-met-overexpressing cells. Overall, our present results revealed that irradiation could induce c-met expression in pancreatic cancer cells, leading to enhanced malignant potential (e.g., invasion and migration ability) and thus promoting distant metastasis. Moreover, a c-Met inhibitor could reverse this enhanced malignant potential.

Breast cancer occurrence after low dose radiotherapy of non-malignant disorders of the shoulder.

Stochastic long-term damages at relatively low doses have the potential for cancer induction. For the first time we investigated the occurrence of breast cancer in female patients after radiotherapy of non-malignant disorders of the shoulder and made a comparison with the estimated spontaneous incidence of mammary carcinoma for this cohort. In a geographically defined district with a population of approximately 100.000 inhabitants, comprehensive data of radiological diagnostics and radiotherapy were registered nearly completely for 41 years; data included mammography and radiotherapy of breast cancer patients as well as of non-malignant disorders. Within this population a collective of 158 women with radiotherapy of the shoulder was investigated. Radiotherapy was performed with cobalt-60 photons (Gammatron) with an average cumulative-dose of 6 Gy. The average follow-up time was 21.3 years. Patients were 55 years old (median) when radiotherapy of the shoulder was performed. Seven patients (4.4%) developed breast cancer after a median of 21 years. According to the incidence statistics, 9.4 +/- 1.8 (95%CI) cases (5.9%) would be expected. In regard to the irradiated shoulder neither the ipsilateral nor the contralateral breasts showed increased rates of breast cancer. An induction of additional breast cancer caused by radiation of non-malignant disorders of the shoulder wasn't detected in the investigated cohort.

Caffeic acid prevents UVB radiation induced photocarcinogenesis through regulation of PTEN signaling in human dermal fibroblasts and mouse skin.

Previously, we proved that caffeic acid (CA), a major dietary phenolic acid, prevents skin carcinogenesis by modulating inflammatory signaling in mouse skin. However, the actual mechanisms of CA against UVB (280-320 nm) induced photocarcinogenesis remains unclear. The present results confirms that CA significantly inhibits single UVB-induced CPDs formation, oxidative DNA damage, ROS generation and frequency of apoptotic cell death in human dermal fibroblasts (HDFa). Furthermore, CA prevents UVB-induced expression of PI3K and AKT kinases through activation of PTEN which subsequently promotes XPC dependant NER proteins such as XPC, XPE, TFIIH (p44) and ERCC1 in HDFa cells and mouse skin tissue. Further, CA directly activates PTEN through hydrogen bond and hydrophobic interactions. Taken together, these findings suggest that CA prevents UVB-induced photodamage through the activation of PTEN expression in human dermal fibroblasts and mouse skin.

Polo-like kinase 1 (Plk1) overexpression enhances ionizing radiation-induced cancer formation in mice.

Polo-like kinase 1 (Plk1), a serine/threonine protein kinase normally expressed in mitosis, is frequently up-regulated in multiple types of human tumors regardless of the cell cycle stage. However, the causal relationship between Plk1 up-regulation and tumorigenesis is incompletely investigated. To this end, using a conditional expression system, here we generated Plk1 transgenic mouse lines to examine the role of Plk1 in tumorigenesis. Plk1 overexpression in mouse embryonic fibroblasts prepared from the transgenic mice led to aberrant mitosis followed by aneuploidy and apoptosis. Surprisingly, Plk1 overexpression had no apparent phenotypes in the mice. Given that no malignant tumor formation was observed even after a long period of Plk1 overexpression, we reasoned that additional factors are required for tumorigenesis in Plk1-overexpressing mice. Because Plk1 can directly participate in the regulation of the DNA damage response (DDR) pathway, we challenged Plk1-overexpressing mice with ionizing radiation (IR) and found that Plk1-overexpressing mice are much more sensitive to IR than their wild-type littermates. Analysis of tumor development in the Plk1-overexpressing mice indicated a marked decrease in the time required for tumor emergence after IR. At the molecular level, Plk1 overexpression led to reduced phosphorylation of the serine/threonine kinases ATM and Chk2 and of histone H2AX after IR treatment both in vivo and in vitro Furthermore, RNA-Seq analysis suggested that Plk1 elevation decreases the expression of several DDR genes. We conclude that Plk1 overexpression may contribute to tumor formation by both inducing chromosomal instability and suppressing the DDR pathway.

Analysis of SDHD promoter mutations in various types of melanoma.

OBJECTIVES: Recently, recurrent mutations in regulatory DNA regions, such as promoter mutations in the TERT gene were identified in melanoma. Subsequently, Weinhold et al. reported SDHD promoter mutations occurring in 10% of melanomas and being associated with a lower overall survival rate. Our study analyzes the mutation rate and clinico-pathologic associations of SDHD promoter mutations in a large cohort of different melanoma subtypes. METHODS: 451 melanoma samples (incl. 223 non-acral cutaneous, 38 acral, 33 mucosal, 43 occult, 43 conjunctival and 51 uveal melanoma) were analyzed for the presence of SDHD promoter mutations by Sanger-sequencing. Statistical analysis was performed to screen for potential correlations of SDHD promoter mutation status with various clinico-pathologic criteria. RESULTS: The SDHD promoter was successfully sequenced in 451 tumor samples. ETS binding site changing SDHD promoter mutations were identified in 16 (4%) samples, of which 5 mutations had not been described previously. Additionally, 5 point mutations not located in ETS binding elements were identified. Mutations in UV-exposed tumors were frequently C>T. One germline C>A SDHD promoter mutation was identified. No statistically significant associations between SDHD promoter mutation status and various clinico-pathologic variables or overall patient survival were observed. CONCLUSIONS: Melanomas harbor recurrent SDHD promoter mutations, which occur primarily as C>T alterations in UV-exposed melanomas. In contrast to the initial report and promoter mutations in the TERT gene, our analysis suggests that SDHD promoter mutations are a relatively rare event in melanoma (4% of tumors) of unclear clinical and prognostic relevance.

Blackberry extract inhibits UVB-induced oxidative damage and inflammation through MAP kinases and NF-κB signaling pathways in SKH-1 mice skin.

Extensive exposure of solar ultraviolet-B (UVB) radiation to skin induces oxidative stress and inflammation that play a crucial role in the induction of skin cancer. Photochemoprevention with natural products represents a simple but very effective strategy for the management of cutaneous neoplasia. In this study, we investigated whether blackberry extract (BBE) reduces chronic inflammatory responses induced by UVB irradiation in SKH-1 hairless mice skin. Mice were exposed to UVB radiation (100 mJ/cm(2)) on alternate days for 10 weeks, and BBE (10% and 20%) was applied topically a day before UVB exposure. Our results show that BBE suppressed UVB-induced hyperplasia and reduced infiltration of inflammatory cells in the SKH-1 hairless mice skin. BBE treatment reduced glutathione (GSH) depletion, lipid peroxidation (LPO), and myeloperoxidase (MPO) in mouse skin by chronic UVB exposure. BBE significantly decreased the level of pro-inflammatory cytokines IL-6 and TNF-α in UVB-exposed skin. Likewise, UVB-induced inflammatory responses were diminished by BBE as observed by a remarkable reduction in the levels of phosphorylated MAP Kinases, Erk1/2, p38, JNK1/2 and MKK4. Furthermore, BBE also reduced inflammatory mediators such as cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2), and inducible nitric oxide synthase (iNOS) levels in UVB-exposed skin. Treatment with BBE inhibited UVB-induced nuclear translocation of NF-κB and degradation of IκBα in mouse skin. Immunohistochemistry analysis revealed that topical application of BBE inhibited the expression of 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodG), cyclobutane pyrimidine dimers (CPD), proliferating cell nuclear antigen (PCNA), and cyclin D1 in UVB-exposed skin. Collectively, these data indicate that BBE protects from UVB-induced oxidative damage and inflammation by modulating MAP kinase and NF-κB signaling pathways.

Chronically sun-damaged melanomas express low levels of nuclear glutathione-S-transferase-π: an epidemiological and clinicopathological study in Italy.

The detoxifying enzyme glutathione-s-transferase pi (GST-π) is present in keratinocytes and melanocytes and exerts a protective role against tumour progression. Melanomas close to melanocytic naevus remnants occur less frequently on sun-exposed areas, whereas solar dermal elastosis, hallmark of chronic sun-damage, characterise melanomas on sun-exposed skin. We evaluated the expression of GST-π in 113 melanomas associated to melanocytic naevus remnants or to solar dermal elastosis, classified according to clinical characteristics, history of sun exposure, histological subtypes and AJCC staging. Chronically sun-damaged melanomas, identified by moderate-severe solar dermal elastosis, showed a lower nuclear GST-π expression and a higher thickness than those related to melanocytic naevus remnants (p < 0.03). Multivariate logistic regression analysis demonstrated that male gender and chronic sun-exposure are independent risk factors significantly associated to melanomas localised on the trunk (OR = 3.36, 95% CI: 1.31-8.65; OR = 5.97, 95% CI: 1.71-20.87). If confirmed on a larger series, lower expression of nuclear GST-π in melanoma cells could represent a possible marker of chronically sun-damaged melanoma pathogenesis.

Matrix metalloproteinase enzymes and their naturally derived inhibitors: novel targets in photocarcinoma therapy.

The continuous exposure of skin to ultraviolet radiations generates reactive oxygen species leading to photoaging in which degradation of dermal collagen and degeneration of elastic fibers occurs. Matrix metalloproteinase [MMP] enzymes are the proteolytic enzymes which have significant potentiality of cleaving extracellular matrix [ECM] against Ultraviolet [UV] radiation. The important MMPs are MMP1, MMP2 and MMP7 which promote skin cancer when irradiated by UV rays. In lieu of this, the investigation of MMPs and their inhibitors are constantly being studied for successive results. Recent researches have focused on some traditionally used bioactive moieties as natural matrix metalloproteinases inhibitors (MMPIs) and emphasized on the need of more extensive and specific studies on MMPIs, so that a good combination of natural or synthetic MMPIs with the conventional drugs can be evolved for cancer chemotherapy. In this review, we discuss the current view on the feasibility of MMPs as targets for therapeutic intervention in cancer. This review also summarizes the role of small molecular weight natural MMPIs and a clinical update of those natural MMPIs that are under clinical trial stage.

[Role of gene polymorphisms of phase II of xenobiotic biotransformation from glutathione-S-transferase and N-acetyltransferase families in susceptibility to lung cancer among Mayak workers].

An association between polymorphous (allelic) gene variants of phase II of enzymatic xenobiotic biotransformation (EXB) of multigene families of glutathione-S-transferase (GSTs) GSTM1*0, GSTT1*0, GSTP1*B Ile105Val, and N-acetyltransferase (NAT) NAT2*6 590G>A, NAT2*5 481C>T, as well as lung cancer in Mayak workers exposed occupationally to prolonged external γ-rays and internal α-radiation from incorporated 239Pu was studied. Analysis of the population frequency of genotypes and alleles of the studied genes in the cohort of Mayak workers revealed their compliance with the Hardy-Weinberg principle and with the corresponding frequency in the European population. The study was based on the case-control method. A case-group consisted of 49 Mayal workers with a verified diagnosis of lung cancer. The mean total absorbed dose from external γ-rays at the moment of diagnostics was 1.03 Gy; the mean total absorbed dose from internal α-radiation from incorporated 239Pu to lung was 0.35 Gy. Control consisted of 172 Mayak workers matched by the year of birth, gender, and age at the moment of employment at one of the main facilities with no lung cancer registered within the study period. No increase in the relative risk of lung cancer (odds ratio, OR) was revealed among the individuals with deletion variants of genes GSTM1*0 and GSTT1*0 (pp genotype, complete absence of gene products) as compared to the individuals with ww or wp genotype, which was determined in total for these genes (normal or partly decreased gene activity). An increase in OR of lung cancer in 1.849 times (p = 0.239) and in 2.439 times (p = 0.075) was found in the carriers with a complete absence of the product of genes GSTP1*B and NAT2*6 590G>A, correspondingly (pp genotype). A statistically significant decrease in OR of lung cancer was found in the wp genotype carriers of gene GSTP1*B (OR = 0.50, p = 0.041). Three variants of paired combinations of gene alleles were established in the carriers with a statistically significant increase in OR of lung cancer (ww GSTP1*B + pp GSTM1*0; ww GSTP1*B + pp NAT2*6 590G>A; pp GSTP1*B + pp NAT2*5 481C>T), and one combination in the carriers with a statistically significant decrease in OR of lung cancer (wp GSTP1*B and ww +wp GSTT1*0).

Inhibitions by hydrogen-occluding silica microcluster to melanogenesis in human pigment cells and tyrosinase reaction.

We investigated the anti-melanogenetic efficacy of hydrogen-occluding silica microcluster (H2-Silica), which is a silsesquioxane-based compound with hydrogen interstitially embedded in a matrix of caged silica, against melanogenesis in HMV-II human melanoma cells and L-DOPA-tyrosinase reaction [EC1.14.18.1]. HMV-II cells were subjected to oxidative stress by ultraviolet ray-A (UVA) exposure of 3-times of 0.65 J/cm2 summed up to 1.95 J/cm2. After UVA irradiation, HMV-II cells were stimulated to produce melanin by 2.72-fold more abundantly than unirradiated control. When HMV-II cells were treated with H2-Silica of 20 ppm or kojic acid of 28.4 ppm before and after UVA-irradiation, the amount of melanin was repressed to 12.2% or 14.5% as compared to that of UVA-irradiated control, respectively. That is, H2-Silica exhibited a comparable efficacy to the whitening agent kojic acid. The H2-Silica could prevent melanogenesis in HMV-II cells by low-level doses at 1-10 ppm, and cell viability and apoptosis event did not change even by high-level doses at 100-1000 ppm. On the contrary, kojic acid was cytotoxic at the concentration of 14-28 ppm or more. By microscopic observation, H2-Silica suppressed such properties indicative of melanin-rich cells as cellular hypertrophy, cell process formation, and melanogenesis around the outside of nuclei. The enzymatic assay using L-DOPA and mushroom tyrosinase demonstrated that H2-Silica restrained UVA-mediated melanin formation owing to down-regulation of tyrosinase activity, which could be attributed to scavenging of free radicals and inhibition of L-DOPA-to-dopachrome oxidation by hydrogen released from H2-Silica. Thus H2-Silica has a potential to prevent melanin production against UVA and serves as a skin-lightening ingredient for supplements or cosmetics.

Predictors of BRAF mutation in melanocytic nevi: analysis across regions with different UV radiation exposure.

BACKGROUND: BRAF mutations have been implicated in initiating promutagenic cellular melanocytic proliferation mostly based on homogeneous Western-based cohorts. Data addressing the possible interaction between exposure to different solar ultraviolet radiation (UVR) magnitudes and BRAF mutation rate (BMR) in melanocytic nevi are limited. DESIGN: Extended BRAF testing for 9 mutations in 225 melanocytic nevus (MN) cases derived from 211 patients from 4 different UVR regions: Lebanon (n = 95; 110 kJ · m(-2) · yr), Syria (n = 23; 93.5 kJ · m(-2) · yr), Kingdom of Saudi Arabia (n = 70; 139 kJ · m(-2) · yr), and Pakistan (n = 37; 118 kJ · m(-2) · yr) was performed. Data collected included age, gender, anatomic location, and lesion size. Histological parameters recorded were MN type (junctional, compound, intradermal, classical blue, cellular blue, compound and intradermal spitz, and congenital) solar elastosis grade, and nevus pigmentation degree. Cumulative 21-year erythemally effective UV averages were derived from The National Center for Atmospheric Research. RESULTS: BRAF mutation status was obtained in 210 cases (6.7% failed polymerase chain reaction). Overall, BMR was 62.4% (131/210) with V600E mutation accounting for 98.5% of cases. Discordant mutation status was found in 2 of 10 patients with multiple nevi. BMR differed significantly, yet nonsystematically, among UVR regions; the highest was detected in nevi coming from Syria (18/23 cases, 78%), followed by Pakistan (21/30 cases, 70%), Kingdom of Saudi Arabia (47/70 cases, 67%), and Lebanon (45/87 cases, 52%). Mutation rates varied significantly across MN type (P < 0.001); the highest rate was recorded in the intradermal nevus type (33/39 cases, 84.6%), followed by the compound (26/32 cases, 81.2%) and congenital (60/74 cases 81.0%) nevi. Stratified by anatomic location, nevi occurring on the face (61/82, 74%) and trunk (58/78, 74%) had more frequent BMRs compared with those occurring on the upper (7/26, 27%) and lower extremities (5/24, 21%, P < 0.001). Severe pigmentation was less frequent in BRAF mutation-positive nevi [5/131 (4%) vs. 34/79 (43%); P < 0.001]. Multivariate independent predictors of BRAF mutation in MN were age [odds ratio (95% confidence interval ) = 1.43 (1.13-1.74) per 10 years; P = 0.004], anatomic location [P = 0.043 overall], and nevus type [P < 0.001 overall]. UVR region was not an independent predictor of BRAF mutation. CONCLUSIONS: Increased BRAF mutation with age along with the lack of a UVR magnitude-BRAF mutation association suggests that duration of exposure rather than UVR exposure dose is the more likely link to acquiring the mutation.

Analysis of NADP+-dependent isocitrate dehydrogenase-1/2 gene mutations in pediatric brain tumors: report of a secondary anaplastic astrocytoma carrying the IDH1 mutation.

Somatic mutations of the isocitrate dehydrogenase-1 gene (IDH1), most commonly resulting in replacement of arginine at position 132 by histidine (p.R132H), have been reported for WHO grade II and III diffuse gliomas and secondary glioblastomas. We investigated IDH1/2 mutations in a retrospective series of 165 pediatric brain tumors, including atypical teratoid/rhabdoid tumors (AT/RT) and choroid plexus tumors, which had not previously been investigated. Mutation analysis was performed by use of pyrosequencing and, additionally, data were validated for a cohort of 70 gliomas from among the series by use of the arrayed primer extension technique. We identified one tumor which harbored mutation of IDH1 at codon 132 and no alteration was identified in the matched-germline DNA. No IDH2 mutations were detected. Most noteworthy, the IDH1 mutant tumor was an anaplastic astrocytoma involving the cortex in the left frontal lobe which appeared seven years after radiation treatment for an extensive sellar/suprasellar craniopharyngioma. This anaplastic astrocytoma was regarded as secondary to radiation treatment because it seemed to originate within the irradiation field that received a dose varying from a maximum of 30.6 Gy of 4 MV X-rays down to very few Gy of lower-energy scattered radiation. In this work our observations agree with those in previous reports showing the rarity of IDH1/2 mutations in childhood tumors. The interesting identification of an IDH1 mutation in a radiation-induced secondary malignant glioma raises the likelihood that these types of tumor may develop IDH1/2 mutations. Thus, caution is needed when dealing with these tumors, and further genetic analysis is warranted.

Fatty acid synthase is a predictive marker for aggressiveness in meningiomas.

Meningiomas are the most frequent intracranial tumors. Although most are benign WHO grade I tumors, grade II and III tumors are aggressive and survival is poor. Treatment options for grade II and III meningiomas are limited, and molecular targets are few. The re-programming of metabolic pathways including glycolysis, lipogenesis, and nucleotide synthesis is a hallmark of the physiological changes in cancer cells. Because fatty acid synthase (FAS), the enzyme responsible for the de-novo synthesis of fatty acids, has emerged as a potential therapeutic target for several cancers, we investigated its involvement in meningiomas. We subjected 92 paraffin-embedded samples from 57 patients with grade I, 18 with grade II and III, and six with radiation-induced tumors to immunohistochemical study of FAS. Whereas its expression was increased in grade II and III meningiomas (62.9 %) compared with grade I tumors (29.8 %) (chi-squared test: p < 0.001), FAS was expressed in grade I tumors with a high MIB-1 index and infiltration into surrounded tissues. All radiation-induced meningiomas expressed FAS and its expression was positively correlated with the MIB-1 index (p < 0.005). Our findings suggest that increased FAS expression reflects the aggressiveness of meningiomas and that it may be a novel therapeutic target for treatment of unresectable or malignant tumors.

Cyclooxygenase-2 (COX-2) mediates arsenite inhibition of UVB-induced cellular apoptosis in mouse epidermal Cl41 cells.

Inorganic arsenic is an environmental human carcinogen, and has been shown to act as a co-carcinogen with solar ultraviolet (UV) radiation in mouse skin tumor induction even at low concentrations. However, the precise mechanism of its co-carcinogenic action is largely unknown. Apoptosis plays an essential role as a protective mechanism against neoplastic development in the organism by eliminating genetically damaged cells. Thus, suppression of apoptosis is thought to contribute to carcinogenesis. It is known that cyclooxygenase-2 (COX-2) can promote carcinogenesis by inhibiting cell apoptosis under stress conditions; and our current studies investigated the potential contribution of COX-2 to the inhibitory effect of arsenite in UV-induced cell apoptosis in mouse epidermal Cl41 cells. We found that treatment of cells with low concentration (5 µM) arsenite attenuated cellular apoptosis upon UVB radiation accompanied with a coinductive effect on COX-2 expression and nuclear factor-κB (NFκB) transactivation. Our results also showed that the COX-2 induction by arsenite and UVB depended on an NFκB pathway because COX-2 co-induction could be attenuated in either p65-deficient or p50-deficient cells. Moreover, UVB-induced cell apoptosis could be dramatically reduced by the introduction of exogenous COX-2 expression, whereas the inhibitory effect of arsenite on UVB-induced cell apoptosis could be impaired in COX-2 knockdown C141 cells. Our results indicated that COX-2 mediated the anti-apoptotic effect of arsenite in UVB radiation through an NFκB-dependent pathway. Given the importance of apoptosis evasion during carcinogenesis, we anticipated that COX-2 induction might be at least partially responsible for the co-carcinogenic effect of arsenite on UVB-induced skin carcinogenesis.

Celecoxib reduces the effects of acute and chronic UVB exposure in mice treated with therapeutically relevant immunosuppressive drugs.

Solid organ transplant recipients have a greatly increased risk for the development of non-melanoma skin cancers. We have previously shown in our mouse model that sirolimus given in combination with cyclosporine A resulted in fewer and smaller tumors than cyclosporine A alone. In the current study, we tested the hypothesis that an anti-inflammatory agent celecoxib applied topically after UVB exposure would further reduce UVB induced skin cancer in mice treated with cyclosporine A and sirolimus. The effect of celecoxib treatment on acute inflammation, initiation/promotion and tumor development was examined through a set of four experiments. Delayed tumor onset was observed in both tumor development experiments. Reduced tumor size and number compared to vehicle was observed when CX was administered concurrently with UVB and when CX was administered after cessation of UVB treatments, respectively. Prostaglandin E2 was confirmed to be significantly reduced in the dorsal skin of mice concurrently treated with immunosuppressants, CX and UVB for 13 weeks, suggesting a reduction in the inflammatory response could be the mechanism by which CX reduced tumorigenesis. Furthermore, topical celecoxib treatment following acute UVB exposure reduced dermal neutrophil number and activity compared to vehicle. In all of these experiments, unirradiated and vehicle treated mice were utilized as controls. In conclusion, these data suggest that even in the presence of cyclosporine A and sirolimus, topical celecoxib treatment can result in reduced inflammation, tumor number and size; properties which may be beneficial in the therapeutic reduction of skin cancer development in solid organ transplant recipients.

NRH:quinone oxidoreductase 2-deficient mice are highly susceptible to radiation-induced B-cell lymphomas.

PURPOSE: NRH:quinone oxidoreductase 2 (NQO2) is known to protect against myelogenous hyperplasia. However, the role of NQO2 in prevention of hematologic malignancies remains unknown. Present studies investigated in vivo role of NQO2 in prevention of myeloproliferative disease and lymphomas. EXPERIMENTAL DESIGN: Wild-type and NQO2-null mice were exposed to 0, 1, and 3 Gy gamma-radiation. One year later, the mice were analyzed for the development of myeloproliferative disease and lymphomas. Immunohistochemistry analysis determined the B- and T-cell origin of lymphomas. The mice were also sacrificed at 6 and 48 h after radiation exposure and bone marrow was collected and analyzed for p53, Bax, and B-cell apoptosis. Bone marrow cells were cultured and the rate of degradation of p53 was analyzed. RESULTS: Seventy-two percent NQO2-null mice showed development of B-cell lymphomas in multiple tissues compared with 11% in wild-type mice exposed to 3 Gy gamma-radiation. In contrast, only 22% NQO2-null mice showed myeloproliferation compared with none in wild-type mice. Further analysis revealed that bone marrow from NQO2-null mice contained lower levels of p53 compared with wild-type mice due to rapid degradation of p53. In addition, the exposure to radiation resulted in lower induction of p53 and Bax and decreased B-cell apoptosis in NQO2-null mice. CONCLUSION: NQO2-null mice are highly susceptible to develop radiation-induced B-cell lymphomas. The lack of significant induction of p53 and Bax and decrease in B-cell apoptosis presumably contributed to the development of lymphomas. NQO2 functions as endogenous factor in prevention against radiation-induced B-cell lymphomas.

Cyclo-oxygenase-2 plays a critical role in UV-induced skin carcinogenesis.

Besides induction of DNA damage and p53 mutations, chronic exposure to UV irradiation leads to the constitutive up-regulation of cyclo-oxygenase-2 (COX-2) expression and to increased production of its primary product in skin, prostaglandin E2 (PGE2). COX-2 has also been shown to be constitutively overexpressed in mouse, as well as human, UV-induced skin cancers and premalignant lesions. UV exposure results in ligand-independent activation of the epidermal growth factor receptor and subsequent activation of mitogen-activated protein kinase and phosphatidylinositol 3-kinase/Akt pathways leading to transcriptional activation of the COX-2 gene. Use of COX-2-specific inhibitors and genetic manipulation of COX-2 expression have demonstrated that UV induction of COX-2 in the skin contributes to the induction of epidermal hyperplasia, edema, inflammation, and counters the induction of apoptosis after UV exposure. Likewise, inhibition of COX-2 activity or reduced expression in COX-2 knockout mice resulted in significantly reduced UV-induced tumorigenesis, while overexpression of COX-2 in transgenic mice enhanced UV-induced tumor development. A combination of signaling from the PGE2 EP1, EP2 and/or EP4 receptors mediates the effects of COX-2 overexpression. These studies demonstrate the crucial role of COX-2 in the development of UV-related nonmelanoma skin cancers.

[Xanthine oxidase activity in the rat liver tissue in the process of oncogenesis].

The work is dedicated to the investigation of xanthine oxidase activity in liver homogenate of rats with tumour at different stages of Guerin carcinoma oncogenesis on the preliminary low-dose irradiation background. Special attention is paid to studying enzyme oxidase form activity, the level of its reactive oxygen species generation and content of thiol groups in protein fraction, which possesses xanthine oxidase activity. The period of Guerin carcinoma active growth is characterized by the increase of total xanthine oxidase activity in the liver. It was found that oxidase activity and the level of O2* generation increase in the preliminary irradiated organism in the period of Guerin carcinoma active growth, as a result of enzyme SH-groups oxidation. At the terminal stages of oncogenesis the decrease of xanthine oxidase activity is accompanied by degradation of the molecule protein part.

Triggering of T-cell leukemia and dissemination of T-cell lymphoma in MMP-9-deficient mice.

Previous studies have shown that high levels of MMP-9 can be detected in the serum of patients with various lymphoid malignancies and in leukemia/lymphoma culture supernatants. Indeed, aggressive forms of lymphoma constitutively produce MMP-9 and its elevated levels in the serum or in tissues correlate with advanced stage and poor patient survival. In vitro, MMP-9, which is also produced by the host peritumoral cells in response to the presence of tumors, plays an important role in migration of tumor cells through artificial basement membranes or endothelial cells. In this study, using MMP-9-deficient mice, we show that absence of MMP-9 does not prevent the development of primary T-cell leukemia. Furthermore, MMP-9-deficient cell lines retained their tumorigenic potential, as shown by their ability to induce thymic lymphoma in young syngeneic wild-type animals. In addition, these MMP-9-deficient tumor cells disseminate in normal mice, or mice that are deficient for MMP-9, indicating that tumor growth and dissemination can occur in total absence of MMP-9. These results show for the first time than lymphoma growth can occur in total absence of MMP-9 and have consequences for therapy of invasive cancers with inhibitors of MMPs.

Inactivation of glutathione peroxidase activity contributes to UV-induced squamous cell carcinoma formation.

Cutaneous squamous cell carcinomas (CSCC) are a common malignancy of keratinocytes that arise in sites of the skin exposed to excessive UV radiation. In the present study, we show that human SCC cell lines, preneoplastic solar keratoses (SK), and CSCC are associated with perturbations in glutathione peroxidase (GPX) activity and peroxide levels. Specifically, we found that two of three SKs and four of five CSCCs, in vivo, were associated with decreased GPX activity and all SKs and CSCCs were associated with an elevated peroxide burden. Given the association of decreased GPX activity with CSCC, we examined the basis for the GPX deficiency in the CSCCs. Our data indicated that GPX was inactivated by a post-translational mechanism and that GPX could be inactivated by increases in intracellular peroxide levels. We next tested whether the decreased peroxidase activity coupled with an elevated peroxidative burden might contribute to CSCC formation in vivo. This was tested in Gpx1(-/-) and Gpx2(-/-) mice exposed to solar-simulated UV radiation. These studies showed that Gpx2 deficiency predisposed mice to UV-induced CSCC formation. These results suggest that inactivation of GPX2 in human skin may be an early event in UV-induced SCC formation.