The radiosensitivity of endothelial cells isolated from human breast cancer and normal tissue in vitro

We developed a novel method for harvesting endothelial cells from blood vessels of freshly obtained cancer and adjacent normal tissue of human breast, and compared the response of the cancer-derived endothelial cells (CECs) and normal tissue-derived endothelial cells (NECs) to ionizing radiation. In brief, when tissues were embedded in Matrigel and cultured in endothelial cell culture medium (ECM) containing growth factors, endothelial cells grew out of the tissues. The endothelial cells were harvested and cultured as monolayer cells in plates coated with gelatin, and the cells of 2nd-5th passages were used for experiments. Both CECs and NECs expressed almost the same levels of surface markers CD31, CD105 and TEM-8 (tumor endothelial marker-8), which are known to be expressed in angiogenic endothelial cells, i.e., mitotically active endothelial cells. Furthermore, both CECs and NECs were able to migrate into experimental wound in the monolayer culture, and also to form capillary-like tubes on Matrigel-coated plates. However, the radiation-induced suppressions of migration and capillary-like tube formations were greater for CECs than NECs from the same patients. In addition, in vitro clonogenic survival assays demonstrated that CECs were far more radiosensitive than NECs. In summary, we have developed a simple and efficient new method for isolating endothelial cells from cancer and normal tissue, and demonstrated for the first time that endothelial cells of human breast cancer are significantly more radiosensitive than their normal counterparts from the same patients.

Endoplasmic reticulum stress-induced JNK activation is a critical event leading to mitochondria-mediated cell death caused by β-lapachone treatment

Background

β-lapachone (β-lap) is a bioreductive agent that is activated by the two-electron reductase NAD(P)H quinone oxidoreductase 1 (NQO1). Although β-lap has been reported to induce apoptosis in various cancer types in an NQO1-dependent manner, the signaling pathways by which β-lap causes apoptosis are poorly understood.

Methodology/Principal Findings

β-lap-induced apoptosis and related molecular signaling pathways in NQO1-negative and NQO1-overexpressing MDA-MB-231 cells were investigated. Pharmacological inhibitors or siRNAs against factors involved in β-lap-induced apoptosis were used to clarify the roles played by such factors in β-lap-activated apoptotic signaling pathways. β-lap leads to clonogenic cell death and apoptosis in an NQO1- dependent manner. Treatment of NQO1-overexpressing MDA-MB-231 cells with β-lap causes rapid disruption of mitochondrial membrane potential, nuclear translocation of AIF and Endo G from mitochondria, and subsequent caspase-independent apoptotic cell death. siRNAs targeting AIF and Endo G effectively attenuate β-lap-induced clonogenic and apoptotic cell death. Moreover, β-lap induces cleavage of Bax, which accumulates in mitochondria, coinciding with the observed changes in mitochondria membrane potential. Pretreatment with Salubrinal (Sal), an endoplasmic reticulum (ER) stress inhibitor, efficiently attenuates JNK activation caused by β-lap, and subsequent mitochondria-mediated cell death. In addition, β-lap-induced generation and mitochondrial translocation of cleaved Bax are efficiently blocked by JNK inhibition.

Conclusions/Significance

Our results indicate that β-lap triggers induction of endoplasmic reticulum (ER) stress, thereby leading to JNK activation and mitochondria-mediated apoptosis. The signaling pathways that we revealed in this study may significantly contribute to an improvement of NQO1-directed tumor therapies.

Aurora-a contributes to radioresistance by increasing NF-kappaB DNA binding

Aurora-A, a serine/threonine kinase that is overexpressed in certain human cancer cell lines, plays an important role in mitotic progression. Aurora-A has also been reported to be involved in the activation of nuclear factor kappa B (NF-kappaB). The purpose of the present study was to identify the role of Aurora-A in the radiation-induced activation pathway of NF-kappaB. Wild-type and Aurora-A knockdown (Aurora-A(KD)) HeLa cells were irradiated with 4 Gy of gamma rays and the EMSA, luciferase reporter gene assay and immunoblot analysis were performed. The siRNA-based gene knockdown and overexpression system was adopted to elucidate the role of Aurora-A in radiation-induced NF-kappaB pathway activation. The clonogenic survival study indicated that Aurora-A(KD) cells and the wild-type cells transfected with Aurora-A siRNA or RelA/p65 siRNA were more radiosensitive than the wild-type cells. In both the wild-type and Aurora-A(KD) cells, radiation caused IkappaB kinase-mediated phosphorylation, degradation of IkappaBalpha and phosphorylation of RelA/p65. The nuclear translocation of RelA/p65 was also similar in the wild-type and Aurora-A(KD) cells. However, RelA/p65-DNA binding was markedly suppressed in Aurora-A(KD) cells compared to that in wild-type cells. It was concluded that Aurora-A enhances the binding of NF-kappaB to DNA, thereby increasing the gene transcription by NF-kappaB and decreasing the radiosensitivity of the cells.

1-Methylxanthine enhances the radiosensitivity of tumor cells

PURPOSE

To determine the efficacy of a caffeine derivative 1-methylxanthine (1-MTX) in increasing radiosensitivity of cancer cells and elucidate the underlying mechanisms in vitro.

MATERIALS AND METHODS

RKO human colorectal cancer cells carrying wild type protein 53 kDa (p53) were incubated with 3 mM 1-MTX for 30 min, exposed to 4 Gy ionizing radiation, and further incubated with 1-MTX for three days. The clonogenic cell death was determined, and the cell cycle distribution and apoptosis were studied with flow cytometry at different times after irradiation. The DNA double strand break (DNA DSB) was examined using phosphorylated Histone2A (gamma-H2AX) foci formation, and the expression/activity of checkpoint 2 kinase (Chk2), cell division cycle 25 (Cdc25) phosphatase and cyclin B1/Cdc2 kinase were also investigated using western blotting and in vitro kinase assays.

RESULTS

The treatment with 3 mM 1-MTX increased the radiation-induced clonogenic and apoptotic cell death. The radiation-induced phosphorylation of Chk2 and Cdc25c and the radiation-induced increase in the cyclin B1/Cdc2 kinas activity were little affected by 1-MTX. The radiation-induced G2/M arrest was only slightly shortened and the expression of radiation-induced gamma-H2AX was markedly prolonged by 1-MTX.

CONCLUSIONS

1-MTX significantly increased the radiosensitivity of RKO human colorectal cancer cells carrying wild type p53 mainly by inhibiting the repair of radiation-induced DNA DSB without causing significant alteration in radiation-induced G2/M arrest. Such a radiosensitization occurred at 1-MTX concentrations almost non-toxic to the target tumor cells.

Radiosensitization of tumor cells by modulation of ATM kinase

PURPOSE

To elucidate the relationship between the radiation-induced activation of ataxia telangiectasia mutated (ATM) kinase, G2 arrest and the caffeine-induced radiosensitization.

METHOD

RKO cells (human colorectal cancer cells) and ATM kinase over-expressing RKO/ATM cells were used. The cellular radiosensitivity was determined with clonogenic survival assay and the cell cycle progression, including G2 arrest, was studied with flow cytometry. The activity of ATM kinase, check point 2 (Chk2) kinase and cycline B1/cell division cycle 2 (Cdc2) kinase was investigated. The radiosensitivity of RKO xenografts grown in nude mice was studied.

RESULTS

RKO/ATM cells were radioresistant as compared with RKO cells. There was a greater increase in ATM kinase activity and G2 arrest in RKO/ATM cells than in RKO cells. Caffeine also sensitized both RKO cells and RKO/ATM cells to radiation. The caffeine treatment suppressed the radiation-induced activation of ATM kinase, suppressed the activation of Chk2 kinase and inhibited the accumulation of cells in G2 phase. The activity of cycline B1/Cdc2 kinase increased earlier but decayed rapidly in the presence of caffeine. Caffeine enhanced radiation-induced growth delay of RKO xenografts.

CONCLUSIONS

Caffeine inhibited the radiation-induced activation of ATM kinase, thereby preventing the accumulation of cells in G2 phase. Consequently, radiosensitivity of cells increased in the presence of caffeine both in vitro and in vivo.

Synergistic effect of ionizing radiation and beta-Lapachone against RKO human colon adenocarcinoma cells

PURPOSE

To reveal the interaction between beta-Lapachone (beta-lap) and ionizing radiation in causing cell death in RKO human colon adenocarcinoma cells, and to elucidate the potential usefulness of combined beta-lap treatment and radiotherapy for cancer treatment.

MATERIALS AND METHODS

The cytotoxicities of various treatments were determined in vitro using clonogenic and apoptotic cell death. The changes in cell cycle distribution were studied using flow cytometry and an in vitro kinase assay. The tumor growth was studied using RKO tumors grown s.c. in the hind leg BALB/c- nuslc nude mice.

RESULTS

beta-Lap caused clonogenic cell death and rapid apoptosis in RKO cells in vitro, in a dose dependent manner. The repair of sublethal radiation damage was almost completely inhibited when cells were maintained in beta-lap during the interval between the two-dose irradiation. Flow cytometry study demonstrated that beta-lap induced apoptosis, independent of the cell cycle phase, and completely prohibited the induction of radiation-induced G2 arrest in irradiated cells. The prohibition of radiation-induced G2 arrest is unclear, but may be related to the profound suppression of the p53, p21 and cyclin B1-Cdc2 kinase activities observed in cells treated with beta-lap. The combination of beta-lap and radiation markedly enhanced the radiation-induced growth suppression of tumors.

CONCLUSION

beta-Lap is cytotoxic against RKO cells, both in vitro and in vivo, and also sensitized cells to ionizing radiation by inhibiting sublethal radiation damage repair. beta-lap is potentially useful as a potent anti-cancer chemotherapy drug and potent radiosensitizer against cancer cells.

Induction of apoptosis by carboplatin and hyperthermia alone or combined in WERI human retinoblastoma cells

This paper investigated the induction of apoptosis and perturbation of cell cycle progression caused by carboplatin (CPt) and hyperthermia alone or combined in WERI human retinoblastoma cells in vitro. An incubation of the cells with 25 or 50 microm of CPt at 37 degrees C caused apoptosis, which progressively increased during the 24-72 h treatment. Hyperthermia at 42.5 degrees C for 1 h induced apoptosis, which became significant from 24 h after the heating. Heating the cells in the presence of CPt and subsequent incubation with CPt was far more effective than treating the cells with hyperthermia or CPt treatment alone in inducing apoptosis in the WERI cells, indicating that the combination of these two modalities is potentially useful for the treatment of retinoblastoma. It appeared that the apoptosis in WERI cells caused by hyperthermia and CPt occurs during G1 phase. An interesting observation was that caspase 9 activation preceded the release of cytochrome C from mitochondria during apoptosis in WERI cells, contrary to the general notion that caspase 9 is activated by cytochrome C.

Influence of environmental pH on G2-phase arrest caused by ionizing radiation

We investigated the effects of an acidic environment on the G2/M-phase arrest, apoptosis, clonogenic death, and changes in cyclin B1-CDC2 kinase activity caused by a 4-Gy irradiation in RKO.C human colorectal cancer cells in vitro. The time to reach peak G2/M-phase arrest after irradiation was delayed in pH 6.6 medium compared to that in pH 7.5 medium. Furthermore, the radiation-induced G2/M-phase arrest decayed more slowly in pH 6.6 medium than in pH 7.5 medium. Finally, there was less radiation-induced apoptosis and clonogenic cell death in pH 6.6 medium than in pH 7.5 medium. It appeared that the prolongation of G2-phase arrest after irradiation in the acidic environment allowed for greater repair of radiation-induced DNA damage, thereby decreasing the radiation-induced cell death. The prolongation of G2-phase arrest after irradiation in the acidic pH environment appeared to be related at least in part to a prolongation of the phosphorylation of CDC2, which inhibited cyclin B1-CDC2 kinase activity.

Neutralization epitopes on the antigenic domain II of the Orientia tsutsugamushi 56-kDa protein revealed by monoclonal antibodies

Monoclonal antibodies (MoAbs) reactive with the authentic Orientia tsutsugamushi 56-kDa protein were generated. MoAb FS10 and FS15 showed in vitro, as well as, in vivo neutralizing activity upon O. tsutsugamushi infection. Deletion mutants of the gene for 56-kDa protein of O. tsutsugamushi Boryong were expressed to map the binding region. FS10 and FS15 are bound to amino acids (aa) located in an antigenic domain II, at residues 140-160 and 187-214, respectively. Computer modeling indicated that aa 146-153 were important for antigenicity against FS10. A sequence for aa 142-150 was highly homologous between oriential strains. These results suggest that the antigenic determinant for neutralizing MoAbs is an epitope within aa 140-160. Furthermore, this region may be important for the adhesion/invasion or intracellular survival of O. tsutsugamushi within host cells.

Apoptosis and cell cycle progression in an acidic environment after irradiation

Apoptosis and cell cycle progression in HL60 cells irradiated in an acidic environment were investigated. Apoptosis was determined by TUNEL staining, PARP cleavage, DNA fragmentation, and flow cytometry. The majority of the apoptosis that occurred in HL60 cells after 4 Gy irradiation took place after G(2)/M-phase arrest. When irradiated with 12 Gy, a fraction of the cells underwent apoptosis in G(1) and S phases while the rest of the cells underwent apoptosis in G(2)/M phase. The apoptosis caused by 4 and 12 Gy irradiation was transiently suppressed in medium at pH 7.1 or lower. An acidic environment was found to perturb progression of irradiated cells through the cell cycle, including progression through G(2)/ M phase. Thus it was concluded that the suppression of apoptosis in the cells after 4-12 Gy irradiation in acidic medium was due at least in part to a delay in cell cycle progression, particularly the prolongation of G(2)/M-phase arrest. Irradiation with 20 Gy indiscriminately caused apoptosis in all cell cycle phases, i.e. G(1), S and G(2)/M phases, rapidly in neutral pH medium and relatively slowly in acidic pH medium. The delay in apoptosis in acidic medium after 20 Gy irradiation appeared to result from mechanisms other than prolonged G(2)/ M-phase arrest.

Disassembly of focal adhesions during apoptosis of endothelial cell line ECV304 infected with Orientia tsutsugamushi

Many bacterial pathogens induce apoptosis in their host cells. We observed the cellular effect of ECV304 cells infected with Orientia tsutsugamushi. The infected cells became rounded and floated in culture supernatant. These floating cells as well as adherent cells exhibited typical features of apoptosis, such as DNA fragmentation and TUNEL staining. As many cells detached from growth substrate, we examined the focal adhesion using the immunofluorescence assay method and observed decreased focal adhesions in heavily infected cells. As endothelial cells could undergo apoptosis by the loss of focal adhesions, this change of focal adhesions may account for the Orientia-induced apoptosis.

Apoptosis of endothelial cell line ECV304 persistently infected with Orientia tsutsugamushi

Endothelial cells are major targets of Orientia tsutsugamushi. To examine the consequences of the infection of endothelial cells with O. tsutsugamushi, we used human endothelial cell line ECV304. Persistent infection was established and infected cultures could be maintained for over seven months without the addition of normal cells. The heavily infected cells became round and floated in the culture medium, harboring large numbers of organisms inside them. Some of the infected ECV304 cells showed features of apoptotic cells, as determined by the terminal deoxytransferase-mediated dUTP nick end-labeling reaction and DNA fragmentation. We also found that O. tsutsugamushi increased transcription of the mRNAs of proinflammatory cytokines such as IL-6 and IL-8. These results show the first evidence of in vitro-persistent infection by O. tsutsugamushi, which may be related to in vivo persistence reported previously.

Pathologic study of mice infected with Rickettsia tsutsugamushi R19 strain

Scrub typhus, an acute febrile infectious disease caused by R. tsutsugamushi, has been reported from various parts of the far east and pacific rim of Asia including Korea. It is well known that all human pathogenic rickettsia share an affinity to endothelial cells of the small blood vessels and evoke vascular inflammation variably associated with a rash, microthrombi, and hemorrhage. We infected the ICR mice by inoculating sublethal doses of R. tsutsugamushi R19 strain intraperitoneally and observed the pathologic changes by time sequence. The histopathologic features of experimentally induced scrub typhus in the mice were generally nonspecific interstitial inflammations characterized by interstitial pneumonitis, periportal inflammation, multifocal hepatic necrosis, interstitial nephritis, sinusoidal engorgement, and lymphohistiocytic cell infiltration in lymph nodes and spleen. Contrary to the general features of other rickettsial diseases, the pathologic process of scrub typhus experimentally induced by R. tsutsugamushi R19 strain mainly involved the interstitial connective tissue but not the blood vessels.

Distribution of HLA class I alleles and haplotypes in Korean

The antigen (phenotype), gene (allele) and haplotype frequencies of HLA class I were analysed in 4,622 Koreans. With allele frequencies of over 0.05, the most frequent HLA-A,-B and -C antigens were A2, A24, A33, A11, A26, A31; B62, B51, B44, B54, B61, B35, B58, B60; Cw3, Cw1, Cw4, Cw7. Of these A2, A24, Cw1 and Cw3 were present in very high frequencies, respectively (0.3211, 0.2200, 0.2204, and 0.3737). The most common haplotypes with frequencies larger than 0.02 were A2-Blank, A33-B44, A33-B58, A11-B62, A24-B51, A24-B54, A2-B27, B54-Cw1, B58-Cw3, B51-Blank, B61-Cw3, B62-Cw4, B35-Cw3, B44-Blank, B60-Cw3, B27-Cw1, A2-Cw3, A2-Cw1, A24-Cw1, A33-Cw3, A26-Cw3, and A11-Cw4. A significant negative linkage disequilibrium was found for the haplotypes of A2-B7, A2-B44, A2-B58, A24-B13, A24-B27, A33-B54 and A33-B62, of which frequencies were larger than 0.003. The B-C and A-C haplotypes which showed the significant negative linkage disequilibrium were B44-Cw1, B51-Cw1, B44-Cw3,B62-Blank, A2-Cw4, A2-Blank, A11-Cw3, A11-Blank and A33-Cw1 and had frequencies higher than 0.01. The findings presented here could be used per se to estimate the populational relationships or as the control data for HLA-disease investigation. Furthermore they could provide the scope for the definition of new antigens.

Molecular characterization of the M genomic segment of the Seoul 80-39 virus; nucleotide and amino acid sequence comparisons with other hantaviruses reveal the evolutionary pathway

The genomic M segment of Seoul 80-39 virus was characterized by cloning and nucleotide sequence analysis. The virion M RNA segment is 3651 nucleotides long with the 3' and 5' terminal sequences inversely complementary for 20 bases. A single open reading frame was detected in the viral complementary-sense RNA which can encode a polypeptide of 1133 amino acids. The Seoul 80-39 virus M segment was compared with the M segments of related viruses, Hantaan 76-118, Hallnas B1 and Sapporo Rat (SR-11) virus. Our results demonstrate a significant similarity between M RNA segments of the Seoul 80-39, Hantaan 76-118, Hallnas B1 and SR-11 viruses. The degree of conservation of both nucleic acid and protein sequences between these viruses reveals a close evolutionary relationship. Furthermore, it is evident that the serotypic profile of hantaviruses is determined by the rodent host species from which the virus was isolated and not by the geographical area.

Nucleotide sequence and coding capacity of the large (L) genomic RNA segment of Seoul 80-39 virus, a member of the hantavirus genus

The nucleotide sequence of the large (L) genomic RNA segment of Seoul 80-39 virus was determined from overlapping cDNA clones. The virion L RNA segment is 6530 nucleotides long. The 3' and 5' terminal sequences are inversely complementary for 15 bases. The viral complementary-sense RNA contains a single open reading frame from an AUG codon at nucleotide position 37-39 to a UAA stop codon at nucleotide position 6490-6492. This ORF could encode a polypeptide of 2151 amino acids (246,662 kDa) which likely corresponds to the L protein detected in purified viral particles (Elliott et al., 1984) and is assumed to be an RNA-dependent RNA polymerase molecule (Schmaljohn and Dalrymple, 1983). Comparison of the L protein of the Seoul 80-39 virus with the polymerase proteins encoded by other negative-stranded RNA viruses revealed 44% similarity only with the part of the Bunyamwera virus L protein (Elliott, 1989) and a very weak homology with the PB1 protein of influenza virus.