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Cellular Sensitivity (cellular + sensitivity)
Selected AbstractsDNA ligase IV is a potential molecular target in ACNU sensitivityCANCER SCIENCE, Issue 8 2010Natsuko Kondo Nimustine (ACNU) is a chloroethylating agent which was the most active chemotherapy agent used for patients with high-grade gliomas until the introduction of temozolomide, which became the standard of care for patients with newly diagnosed glioblastomas in Japan. Since temozolomide was established as the standard first-line therapy for glioblastoma multiforme (GBM), ACNU has been employed as a salvage chemotherapy agent for recurrent GBM in combination with other drugs. The acting molecular mechanism in ACNU has yet to be elucidated. ACNU is a cross-linking agent which induces DNA double-strand breaks (DSBs). The work described here was intended to clarify details in repair pathways which are active in the repair of DNA DSBs induced by ACNU. DSBs are repaired through the homologous recombination (HR) and non-homologous end-joining (NHEJ) pathways. Cultured mouse embryonic fibroblasts were used which have deficiencies in DNA DSB repair genes which are involved in HR repair (X-ray repair cross-complementing group 2 [XRCC2] and radiation sensitive mutant 54 [Rad54]), and in NHEJ repair (DNA ligase IV [Lig4]). Cellular sensitivity to ACNU treatment was evaluated with colony forming assays. The most effective molecular target which correlated with ACNU cell sensitivity was Lig4. In addition, it was found that Lig4 small-interference RNA (siRNA) efficiently enhanced cell lethality which was induced by ACNU in human glioblastoma A172 cells. These findings suggest that the down-regulation of Lig4 might provide a useful tool which can be used to increase cell sensitivity in response to ACNU chemotherapy. (Cancer Sci 2010) [source] Hyperphosphorylation of replication protein A in cisplatin-resistant and -sensitive head and neck squamous cell carcinoma cell linesHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 5 2010Karoline C. Manthey MS Abstract Background Resistance to chemotherapy is a major limitation in the treatment of head and neck squamous cell carcinomas (HNSCCs), accounting for high mortality rates in patients. Here, we investigated the role of replication protein A (RPA) in cisplatin and etoposide resistance. Methods We used 6 parental HNSCC cell lines. We also generated 1 cisplatin-resistant progeny subline from a parental cisplatin-sensitive cell line, to examine cisplatin resistance and sensitivity with respect to RPA2 hyperphosphorylation and cell-cycle response. Results Cisplatin-resistant HNSCC cell levels of hyperphosphorylated RPA2 in response to cisplatin were 80% to 90% greater compared with cisplatin-sensitive cell lines. RPA2 hyperphosphorylation could be induced in the cisplatin-resistant HNSCC subline. The absence of RPA2 hyperphosphorylation correlated with a defect in cell-cycle progression and cell survival. Conclusion Loss of RPA2 hyperphosphorylation occurs in HNSCC cells and may be a marker of cellular sensitivities to cisplatin and etoposide in HNSCC. © 2009 Wiley Periodicals, Inc. Head Neck, 2010 [source] Enhanced sensitivity to DNA damage induced by cooking oil fumes in human OGG1 deficient cellsENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 4 2008Mei Wu Abstract Cooking oil fumes (COFs) have been implicated as an important nonsmoking risk factor of lung cancer in Chinese women. However, the molecular mechanism of COFs-induced carcinogenicity remains unknown. To understand the molecular basis underlying COFs-induced cytotoxicity and genotoxicity as well as the roles of hOGG1 in the repair of COFs-induced DNA damage, a human lung cancer cell line with hOGG1 deficiency, A549-R was established by using a ribozyme gene targeting technique that specifically knockdowned hOGG1 in A549 lung adenocarcinoma cells. MTT and comet assays were employed to examine cell viability and DNA damage/repair, respectively, in A549-R and A549 cell lines treated with COF condensate (COFC). RT-PCR and Western blot results showed that the expression of hOGG1 in A549-R cell line was significantly decreased compared with that in A549 cell line. The concentration of COFC that inhibited cell growth by 50% (the IC50) in the A549-R cell line was much lower than that in the A549 cell line, and more COFC-induced DNA damage was detected in the A549-R cell line. The time course study of DNA repair demonstrated delayed repair kinetics in the A549-R cell line, suggesting a decreased cellular damage repair capacity. Our results showed that hOGG1 deficiency enhanced cellular sensitivity to DNA damage caused by COFC. The results further indicate that hOGG1 plays an important role in repairing COF-induced DNA damage. Our study suggests that COFs may lead to DNA damage that is subjected to hOGG1 -mediated repair pathways, and oxidative DNA damage may be involved in COF-induced carcinogenesis. Environ. Mol. Mutagen., 2008. © 2008 Wiley-Liss, Inc. [source] BRCA1 modulates malignant cell behavior, the expression of survivin and chemosensitivity in human breast cancer cells,INTERNATIONAL JOURNAL OF CANCER, Issue 12 2009Moltira Promkan Abstract BRCA1 is a multifunctional tumor-suppressive protein. Many functional aspects of BRCA1 are not fully understood. We used a shRNA approach to probe the function of BRCA1 in human breast cancer cells. Knocking down BRCA1 expression by shRNA in the wild-type BRCA1 human breast cancer MCF-7 and MDA-MB-231 cells resulted in an increase in cell proliferation, anchorage-independent growth, cell migration, invasion and a loss of p21/Waf1 and p27Kip1 expression. In BRCA1 knocked-down cells, the expression of survivin was significantly up regulated with a concurrent decrease in cellular sensitivity to paclitaxel. We also found that cells harboring endogenous mutant or defective BRCA1 (MDA-MB-436 and HCC1937) were highly proliferative and expressed a relatively low level of p21/Waf1 and p27Kip1 by comparison to wild-type BRCA1 cells. Cells harboring mutated BRCA1 also expressed a high level of survivin and were relatively resistant to paclitaxel by comparison to wild-type cells. Increase resistance to paclitaxel was due to an increase in the expression of survivin in both the BRCA1 knocked-down and mutant BRCA1 cells because knocking down survivin expression by siRNA restored sensitivity to paclitaxel. We conclude that BRCA1 down-modulates the malignant behavior of breast cancer cells, promotes the expression of p21/Waf1, p27Kip1 and inhibits the expression of survivin. Moreover, loss of BRCA1 expression or function leads to an increase in survivin expression and a reduction in chemosensitivity to paclitaxel. © 2009 UICC [source] Elevation of XPA protein level in testis tumor cells without increasing resistance to cisplatin or UV radiationMOLECULAR CARCINOGENESIS, Issue 8 2008Beate Köberle Abstract Most testicular germ cell tumors are curable using cisplatin-based chemotherapy, and cell lines from these tumors are unusually sensitive to cisplatin and other DNA-damaging agents. It has been suggested that this might be caused by a lower-than normal nucleotide excision repair (NER) activity. Previous studies found that cell lines from testicular germ cell tumors have on average about one-third the level of the NER protein XPA in comparison to cell lines from other tumors. We asked whether over-expression of XPA protein would alleviate the cellular sensitivity and increase the DNA repair capacity of a testis tumor cell line. Increasing XPA levels in 833K cells by 10-fold did not increase resistance to UV irradiation. XPA was localized to the cell nucleus in all cell lines, before and after exposure to UV-radiation. 833K cells were proficient in removing UV radiation-induced photoproducts from the genome and increased XPA did not enhance the rate of removal. Further, over-expressing functional XPA protein did not correlate with increased resistance of 833K testis tumor cells to cisplatin. Thus, although the amount of XPA in this testis tumor cell line is lower than normal, it is sufficient for NER in vivo. The relative sensitivity of testis tumor cells to cisplatin, UV radiation, and other DNA damaging agents is likely related not to NER capacity, but to other factors such as the integrity of the p53 pathway in these cells. © 2008 Wiley-Liss, Inc. [source] Brassinosteroids as Metahormones: Evidence for their Specific Influence during the Critical Period in Sorghum DevelopmentPLANT BIOLOGY, Issue 6 2002G. N. Amzallag Abstract: In Sorghum bicolor, the effect of brassinosteroid (BR) treatments on blade elongation depends both on concentration and on the stage of development. A specific period of increase in sensitivity to BR is reported during early vegetative development. It coincides with emergence of a critical period during which the between-organs relationship is readjusted as a function of new developmental events or new environmental conditions. Accordingly, the influence of BR cannot be completely understood without separating its effects during stable phases (phenophases) and during critical periods. A high level of redundancy exists in networks of regulation, so that modifications due to BR treatments generally remain cryptic. Nevertheless, it is shown that BR affects the pattern of relationships between organs, confirming its involvement in emergence of a new network of regulation. It is suggested that, during critical periods, brassinosteroids act as "metahormones" integrating the new emerging regulation network by triggering changes in cellular sensitivity to PGRs. [source] Anti-miR-21 oligonucleotide sensitizes leukemic K562 cells to arsenic trioxide by inducing apoptosisCANCER SCIENCE, Issue 4 2010Yumin Li Arsenic trioxide (ATO), an ancient traditional Chinese medicine, has been successfully used as a therapeutic agent for leukemia. Drug resistance and toxicity are major concerns with the treatment. MicroRNAs (miRNAs) are endogenous small non-coding RNA molecules that might modulate cellular sensitivity to anticancer drugs. miRNA-21 (miR-21) is one of the most prominent miRNAs involved in various aspects of human cancers. However, miR-21 has been rarely characterized in chronic myelogenous leukemia (CML). Here, we used a specific anti-miR-21 oligonucleotide (AMO-miR-21) to sensitize K562 cells to ATO by degradation of miR-21. The results showed that both AMO-miR-21 and ATO caused growth inhibition, apoptosis, and G1-phase arrest in K562 cells. Meanwhile, AMO-miR-21 significantly promoted ATO-mediated growth inhibition and apotosis without affecting the G1 phase. Apoptotic cells were confirmed morphologically with Giemsa's staining. Furthermore, dual-luciferase reporter vector, containing two tandem miR-21 binding sites from PDCD4 3,UTR, validated that PDCD4 was directly regulated by miR-21. Therefore, AMO-miR-21 sensitized leukemic K562 cells to ATO by inducing apoptosis partially due to its up-regulation of PDCD4 protein level. The combination of ATO and AMO-miR-21 present therapeutic potential for CML. (Cancer Sci 2010; 101: 948,954) [source] Epidermal growth factor receptor lacking C-terminal autophosphorylation sites retains signal transduction and high sensitivity to epidermal growth factor receptor tyrosine kinase inhibitorCANCER SCIENCE, Issue 3 2009Mari Maegawa Constitutively active mutations of epidermal growth factor receptor (EGFR) (delE746_A750) activate downstream signals, such as ERK and Akt, through the phosphorylation of tyrosine residues in the C-terminal region of EGFR. These pathways are thought to be important for cellular sensitivity to EGFR tyrosine kinase inhibitors (TKI). To examine the correlation between phosphorylation of the tyrosine residues in the C-terminal region of EGFR and cellular sensitivity to EGFR TKI, we used wild-type (wt) EGFR, as well as the following constructs: delE746_A750 EGFR; delE746_A750 EGFR with substitution of seven tyrosine residues to phenylalanine in the C-terminal region; and delE746_A750 EGFR with a C-terminal truncation at amino acid 980. These constructs were transfected stably into HEK293 cells and designated HEK293/Wt, HEK293/D, HEK293/D7F, and HEK293/D-Tr, respectively. The HEK293/D cells were found to be 100-fold more sensitive to EGFR TKI (AG1478) than HEK293/Wt. Surprisingly, the HEK293/D7F and HEK293/D-Tr cells, transfected with EGFR lacking the C-terminal autophosphorylation sites, retained high sensitivity to EGFR TKI. In these three high-sensitivity cells, the ERK pathway was activated without ligand stimulation, which was inhibited by EGFR TKI. In addition, although EGFR in the HEK293/D7F and HEK293/D-Tr cells lacked significant tyrosine residues for EGFR signal transduction, phosphorylation of Src homology and collagen homology (Shc) was spontaneously activated in these cells. Our results indicate that tyrosine residues in the C-terminal region of EGFR are not required for cellular sensitivity to EGFR TKI, and that an as-yet-unknown signaling pathway of EGFR may exist that is independent of the C-terminal region of EGFR. (Cancer Sci 2009; 100: 552,557) [source] | |||||||||||||