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Biomedical subjects

Hoguen Kim

Publications and source records attributed to Hoguen Kim.

At least 19 recordsLinked to original sources
PubMed2007

Identical epidermal growth factor receptor mutations in adenocarcinomatous and squamous cell carcinomatous components of adenosquamous carcinoma of the lung.

BACKGROUND: Adenosquamous carcinoma of the lung is composed of adenocarcinomatous and squamous cell carcinomatous components. The epidermal growth factor receptor (EGFR) mutations occur mostly in adenocarcinomas and rarely in squamous cell carcinoma of lung. Attempts to investigate the EGFR mutation status in each component of adenosquamous carcinoma and to characterize the patients according to mutation status may help to understand the histogenesis of adenosquamous carcinoma. METHODS: The mutation status of EGFR kinase domain from exon 18 to 21 was investigated in 25 Korean patients with adenosquamous carcinoma by polymerase chain reaction-single strand conformation polymorphism using the tissues of each component from the adenosquamous carcinoma tumor. Clinicopathologic characteristics of the patients according to the status of EGFR mutations were compared. RESULTS: EGFR mutations were identified in 11 (44%) patients: 9 mutations were in exon 19, 1 in exon 20, and 1 in exon 21. EGFR mutations were significantly more frequent (P = .005) in women (n = 8, 80%) than men (n = 3, 20%). Never-smokers (n = 8, 62%) had EGFR mutations more commonly than smokers (n = 3, 25%; P = .111). Identical EGFR mutations in both components of adenosquamous carcinoma were confirmed by nucleotide sequencing. CONCLUSIONS: The frequency of EGFR mutation and clinicopathologic characteristics of the EGFR mutants in adenosquamous carcinoma are similar to those of Asian patients with adenocarcinomas. Identical EGFR mutations in both components suggest the possibility of monoclonality in the histogenesis of adenosquamous carcinoma.

Adenocarcinoma↗
PubMed2006

Prognostic significance of circumferential resection margin following total mesorectal excision and adjuvant chemoradiotherapy in patients with rectal cancer.

BACKGROUND: This study was designed to evaluate the prognostic value of circumferential resection margin (CRM) in rectal cancer patients who underwent curative resection with adjuvant chemoradiotherapy (CRT). METHODS: We studied 504 patients who underwent total mesorectal excision with adjuvant CRT for rectal cancer between 1997 and 2001. The patients were divided into two groups: a negative CRM group (CRM > 1 mm) and a positive CRM group (CRM <or= 1 mm). The survival rates, local recurrence rates, and systemic recurrence rates were compared between groups. RESULTS: The negative CRM group had 460 patients and the positive CRM group had 44 patients. The 5-year local and systemic recurrence rates were 11.3 and 25.3%, respectively, in the negative CRM group and 35.2 and 60.8% in the positive CRM group, respectively. The cancer-specific 5-year survival rates for the two groups were 72.5 and 26.9% (P < .001), respectively. CRM was found to be an independent prognostic factor by multivariate analyses which were adjusted for known outcome predictors (P < .001). CONCLUSION: Oncological outcome for patients in the positive CRM group is less favorable than for those in the negative CRM group. Adjuvant CRT is not a definite treatment modality that can be used to compensate for a positive CRM following TME and adjuvant CRT in patients with TNM stage II or III rectal cancer.

Adenocarcinoma↗
PubMed2006

Relaxin expression from tumor-targeting adenoviruses and its intratumoral spread, apoptosis induction, and efficacy.

BACKGROUND: The use of oncolytic adenoviruses as cancer gene therapy is limited by their uneven penetration and distribution in tumors. We investigated whether the expression of the cell matrix-degradative protein relaxin by adenovirus could improve adenovirus distribution and penetration in tumors. METHODS: We generated relaxin-expressing, replication-incompetent (dl-lacZ-RLX) and -competent (Ad-deltaE1B-RLX) adenoviruses by inserting a relaxin gene into the E3 adenoviral region. Controls were parental adenoviruses (dl-lacZ and Ad-deltaE1B) and phosphate-buffered saline (PBS) (vehicle). Replication-incompetent viruses, which do not lyse cells, were used to assess transduction efficiency. Viral spread in tumor spheroids, made by dissecting tumor tissue into homogeneous fragments, was assessed by reporter gene (i.e., lacZ) expression. Tumor growth inhibition was assessed by injecting adenoviruses into xenograft tumors in athymic mice (n = 8 or 9). Overall survival was assessed by the Kaplan-Meier method. Extracellular matrix was examined with Masson's trichrome staining. Therapeutic efficacy was evaluated by assessing spontaneous pulmonary metastasis in the B16BL6 melanoma mouse model and growth inhibition of orthotopically implanted hepatoma (n = 4-6). All statistical tests were two-sided. RESULTS: In tumor spheroids and established solid tumors in vivo, transduction with dl-lacZ-RLX, compared with parental virus or vehicle, elicited higher transduction efficiency and viral spread throughout the tumor mass. Infection with Ad-deltaE1B-RLX, compared with parental virus, elicited greater viral persistence and spread, leading to increased survival (e.g., 100%, 95% confidence interval [CI] = 63.1% to 100%, for C33A tumor-bearing mice treated with Ad-deltaE1B-RLX, and 50%, 95% CI = 15.7% to 84.3%, for C33A tumor-bearing mice treated with Ad-deltaE1B). Infection with Ad-deltaE1B-RLX substantially decreased the collagen content of tumor tissue but not of adjacent normal tissue, compared with noninfected tissues. Intratumoral injection of Ad-deltaE1B-RLX inhibited the formation of lung metastases in mice (PBS = 268 mg of metastatic tumor per mouse and Ad-deltaE1B-RLX = 10 mg; difference = 258 mg, 95% CI = 94 to 426; P = .003, Mann-Whitney test). Systemic treatment with Ad-deltaE1B-RLX completely inhibited the growth of Hep1 hepatocellular carcinomas (PBS = 20.2 mg of tumor per mouse and Ad-deltaE1B-RLX = 0 mg; difference = 20.2 mg, 95% CI = 3.7 to 36.7; P = .004, Mann-Whitney test). CONCLUSION: Extracellular matrix degradation by relaxin expressed by adenoviruses increased viral distribution and tumor penetration, inhibited tumor growth and metastasis, and increased survival of mice.

Adenoviridae↗
PubMed2006

Enhanced antitumor effect of oncolytic adenovirus expressing interleukin-12 and B7-1 in an immunocompetent murine model.

PURPOSE: We investigated whether an armed viral platform, where lytic property of a viral infection is coupled to viral-mediated delivery of therapeutic genes, could increase the therapeutic potential of a viral-based therapy. EXPERIMENTAL DESIGN: We generated interleukin (IL)-12-expressing oncolytic adenovirus (YKL-IL-12) and IL-12- and B7-1-expressing (YKL-IL12/B7) oncolytic adenovirus. Therapeutic efficacy of these newly engineered adenoviruses was then evaluated in vivo using an immunocompetent mouse bearing murine melanoma B16-F10 tumors. Overall survival was assessed with the Kaplan-Meier method. The induction of immune cell cytotoxicity was assessed by CTL assay, IFN-gamma enzyme-linked immunospot assay, and immunohistochemical studies. RESULTS: YKL-IL12/B7 oncolytic adenovirus, expressing both IL-12 and B7-1, showed a higher incidence of complete tumor regression compared with the analogous oncolytic adenovirus, YKL-1, or IL-12-expressing, YKL-IL12. Significant survival advantage was also seen in response to YKL-IL12/B7. Moreover, IL-12 and IFN-gamma levels produced in tumors treated with YKL-IL12/B7 was significantly greater than those treated with YKL-IL12. The enhanced survival advantage was mediated by the induction of immune cell cytotoxicity. In agreement with these results, massive infiltration of CD4(+) and CD8(+) T cells into tissues surrounding the necrotic area of the tumor was observed following in situ delivery of YKL-IL12/B7. CONCLUSION: Combination of oncolysis and the enhancement of antitumor immune response by oncolytic adenovirus expressing both IL-12 and B7-1 elicits potent antitumor effect and survival advantage.

Adenoviridae↗
PubMed2006

Differentially expressed proteins in gastrointestinal stromal tumors with KIT and PDGFRA mutations.

Most gastrointestinal stromal tumors (GIST) have activating mutations in either KIT or PDGFRA. However, a small subset of GIST lacks either mutation. To investigate the molecular characteristics of GIST according to mutation type, protein expression profiles in 12 GIST (2 cases with PDGFRA mutations, 8 cases with KIT mutations and 2 cases lacking either mutation) were analyzed using 2-DE and MALDI-TOF-MS. Comparative analysis of the respective spot patterns using 2-DE showed that 15 proteins were differently expressed according to the mutation status. Expression levels of septin and heat shock protein (HSP) 27 were increased in GIST with KIT mutations and annexin V was overexpressed in GIST lacking either mutation. Among the 15 proteins, overexpression of 5 proteins [annexin V, high mobility group protein 1 (HMGB1), C13orf2, glutamate dehydrogenase 1 and fibrinogen beta chain] and decreased expression of RoXaN correlated with a higher tumor grade. These findings suggest that differential protein expression can be used as a diagnostic biomarker. Moreover, it may play a role in the development and progression of GIST according to activating mutation type, as these proteins have been shown to be involved in tumor metastasis, apoptosis and immune response.

Electrophoresis, Gel, Two-Dimensional↗
PubMed2006

Suppression of human selenium-binding protein 1 is a late event in colorectal carcinogenesis and is associated with poor survival.

The purpose of this study was to analyze altered protein expression in cancer tissues and determine its relationship to prognosis in colorectal carcinomas. We performed proteomic expression analysis on 14 colorectal carcinomas and matched nontumorous colonic mucosa by 2-DE and MALDI-TOF-MS. Comparative analysis of the respective spot patterns on 2-DE showed 14 spots that were markedly changed in the colorectal carcinomas. Among them, selenium-binding protein 1 (SELENBP1) was markedly decreased in 12 (85%) carcinomas. The reduced expression of SELENBP1 was further supported by Western blot analysis and immunohistochemistry. Suppression of SELENBP1 was further analyzed in another eight-paired adenomas and carcinomas from the same patients using Western blot analysis and immunohistochemistry, and revealed that one adenoma and seven carcinomas exhibited markedly reduced SELENBP1 expression. Patients with low levels of SELENBP1 expression had significantly lower overall survival rates (72 vs. 85%, p = 0.021) among the 240 stages II and III colorectal carcinomas by using tissue microarray analysis. Our findings indicate that suppression of SELENBP1 is a frequent and late event in colorectal carcinogenesis, and may contribute to the rapid progression of colorectal carcinoma.

Adenoma↗
PubMed2006

Markedly enhanced cytolysis by E1B-19kD-deleted oncolytic adenovirus in combination with cisplatin.

Oncolytic adenoviruses are currently being developed as novel antitumor therapeutics. To enhance their therapeutic potential, adenoviruses are being administered in combination with standard chemotherapy. Adenoviral vectors used in these clinical trials, however, can be destructive as they encode intact E1B 19-kDa protein, which can block the apoptotic pathway induced by a variety of chemotherapeutic agents. Previously, we have shown that oncolytic adenovirus Ad-DeltaE1B19/55, deleted for sequence encoding E1B 19-kDa and E1B 55-kDa proteins, exhibits marked enhancement in cytolytic and apoptotic activity [Kim, J., Cho, J.Y., Kim, J.H., Jung, K.C., and Yun, C.O. (2002). Cancer Gene Ther. 9, 725-736]. In the current study, we assess the therapeutic value of Ad- DeltaE1B55 and Ad-DeltaE1B19/55 in combination with cisplatin. A marked increase in cytotoxicity was observed for both Ad-DeltaE1B55 and Ad-DeltaE1B19/55 when combined with cisplatin. Relative to each other in all cell lines examined, the combination of the double-deleted adenovirus, Ad-DeltaE1B19/55, plus cisplatin exhibited a greater cell-killing effect than did the single-deleted adenovirus, Ad-DeltaE1B55, plus cisplatin. Propidium iodide staining and TUNEL analysis also revealed that the combination of cisplatin with Ad-DeltaE1B19/55 caused greater induction of apoptosis than that with Ad-DeltaE1B55. Similarly, in vivo, the combination of Ad-DeltaE1B55 or Ad-DeltaE1B19/55 with cisplatin also induced greater antitumor effect in a human cervical xenograft model. TUNEL staining showed that the apoptotic level was significantly higher in tumor tissue treated with Ad-DeltaE1B19/55 plus cisplatin than with any other treatment. In addition, viral presence was confirmed by immunohistological staining, with increased numbers of adenoviral particles detected in wider areas of tumors treated with Ad-DeltaE1B19/55 oncolytic adenovirus plus cisplatin. Taken together, these findings demonstrate that cisplatin in combination with E1B- 19kD-deleted oncolytic adenovirus may enhance therapeutic efficacy (via active induction of apoptosis), eliciting a greater efficacy profile than that with E1B-19kD-expressing oncolytic adenovirus.

Adenoviridae↗
PubMed2006

Solid pseudopapillary tumor of the pancreas suggesting malignant potential.

OBJECTIVES: It has been suggested that the histopathologic features associated with malignant potential in solid pseudopapillary tumors (SPTs) of the pancreas include cellular polymorphism, mitotic activity, peripancreatic tissue invasion, neural invasion, lymphovascular invasion, and lymph node metastasis. This study aimed to delineate the features predicting SPTs with malignant potential, which can be easily assessed in the clinical setting, and long-term results of patients who underwent resection of SPT. METHODS: A retrospective review and analysis were done of 33 patients who had SPTs that were surgically treated. RESULTS: Eleven patients (33.3%) had SPTs suggesting malignant potential among surgically treated patients with SPTs. The local invasion to the peripancreatic tissue was the most frequent malignant pathological feature (7/11 patients, 63.7%). Using univariate analysis, tumor size greater than 5 cm was a significant clinical factor to predict SPTs with malignant potential (P = 0.022). The prognosis was excellent. No statistically significant survival difference was noted between groups of malignant potential and benign pathology (P = 0.1904). CONCLUSIONS: Malignant SPTs are low-grade tumors with good prognosis. Adequate surgical intervention is necessary. Especially, SPTs over 5 cm in diameter need to be treated carefully because of the chance of malignant pathology. Careful long-term follow-up is necessary in those patients in case of possible tumor recurrences.

Adolescent↗
PubMed2006

Oncologic outcomes after neoadjuvant chemoradiation followed by curative resection with tumor-specific mesorectal excision for fixed locally advanced rectal cancer: Impact of postirradiated pathologic downstaging on local recurrence and survival.

OBJECTIVE: The purpose of this study was to determine the oncologic outcomes and clinical factors affecting survival in patients who underwent neoadjuvant chemoradiotherapy following tumor specific mesorectal excision for locally advanced, fixed rectal cancer. SUMMARY BACKGROUND DATA: Neoadjuvant chemoradiation therapy has resulted in significant tumor downstaging, which enhances curative resection and subsequently improves local disease control for rectal cancer. However, oncologic outcomes, according to clinical factors, have not yet been fully understood in locally advanced and fixed rectal cancer. METHODS: A total of 114 patients who had undergone neoadjuvant chemoradiation for advanced rectal cancer (T3 or T4 and node positive) were investigated retrospectively. Chemotherapy was administered intravenously with 5-FU and leucovorin during weeks 1 and 5 of radiotherapy. The total radiation dose was 5040 cGY in 25 fractions delivered over 5 weeks. Tumor-specific mesorectal excision was done 4 to 6 weeks after the completion of neoadjuvant chemoradiation. Survival and recurrence rates, according to the pathologic stage, were evaluated. Moreover, factors affecting survival were investigated. RESULTS: The 5-year survival rates according to pathologic stage were: 100% in pathologic complete remission (n = 10), 80% in stage I (n = 23), 56.8% in stage II (n = 34), and 42.3% in stage III (n = 47) (P = 0.0000). Local, systemic, and combined recurrence rates were 11.4%, 22.8%, and 3.5%, respectively. Multivariate analysis showed that the pathologic N stage and operation method were the independent factors affecting survival rate. CONCLUSION: Pathologic complete remission showed excellent oncologic outcomes, and the pathologic N stage was the most important factor for oncologic outcomes.

Adult↗
PubMed2005

Co-induction of cell death and survival pathways by phosphoinositide 3-kinase.

A single stimulus can induce both the cell death and survival pathway, suggesting that these pathways share common upstream signaling components. In order to define these components, human U937 cells grown in 10% serum were exposed to serum-free media. This treatment resulted in apoptosis, which was found to be mediated by SAPK/JNK. It was previously reported that the serum withdrawal (SW)-induced SAPK activation is mediated by a positive mutual interaction between the reactive oxygen species (ROS) and phosphoinositide 3-kinase (PI3K). This study shows that the ROS/PI3K interaction also induces a NF-kappaB-dependent survival pathway. Despite the role of PI3K, Akt was found to be irrelevant to the activation of SAPK and NF-kappaB. Comparative analyses of SAPK and NF-kappaB for their responses to exogenous H(2)O(2) revealed that SAPK activation requires much higher H(2)O(2) concentrations than those required for NF-kappaB activation. Moreover, high lethal concentrations of H(2)O(2) were found to activate NF-kappaB and SAPK in a PI3K-independent manner. These results suggest that ROS induce both the SAPK-dependent apoptotic and NF-kappaB-mediated survival pathways, and these inducer signals are amplified by PI3K in the SW-triggered pathway. Cell death appears to be favored as this amplification proceeds.

Blotting, Western↗
PubMed2005

Tumor-associated alterations in caspase-14 expression in epithelial malignancies.

PURPOSE: Caspase-14 is unique among caspase family proteases in that its proteolytic processing has been principally associated with epithelial cell differentiation rather than apoptosis or inflammation. We investigated caspase-14 expression in several types of human epithelial malignancy by immunohistochemistry, correlating results with stage, histologic grade, and patient survival. EXPERIMENTAL DESIGN: Tumor-associated alterations in caspase-14 expression were observed for cervical, ovarian, breast, gastric, and colon cancers. RESULTS: In cervical (n = 445), ovarian (n = 91), and colon (n = 106) specimens, expression of caspase-14 was significantly reduced in cancers compared with normal epithelium. Decreases in caspase-14 immunopositivity correlated with the histologic progression of cervical cancer (P < 0.0001, ANOVA). In localized gastric cancers, caspase-14 immunostaining was significantly lower in poorly differentiated tumors compared with well-differentiated tumors (P = 0.02, Pearson's chi(2) analysis). Lower caspase-14 expression was associated with advanced clinical stage in ovarian cancer (P = 0.04, ANOVA) and with shorter overall survival among ovarian cancer patients with serous tumors (n = 62) in both univariate (P = 0.005) and multivariate (P = 0.03) analysis. Lower caspase-14 expression correlated with shorter overall survival among patients with T(3)N(0)M(0) stage gastric cancers (n = 94; P = 0.006, log-rank test). In contrast to cervical, ovarian, and colon cancers, caspase-14 expression was increased in ductal carcinoma in situ and invasive cancers compared with normal mammary epithelium (P = 0.001, t test). CONCLUSIONS: The findings reveal tumor-specific alterations in caspase-14 expression and suggest that differences in its expression may define subsets of epithelial cancers with distinct clinical behaviors.

Biomarkers, Tumor↗
PubMed2005

Analysis of apoptosis protein expression in early-stage colorectal cancer suggests opportunities for new prognostic biomarkers.

PURPOSE: Although most stage II colon cancers are potentially curable by surgery alone, approximately 20% of patients relapse, suggesting a need for establishing prognostic markers that can identify patients who may benefit from adjuvant chemotherapy. We tested the hypothesis that differences in expression of apoptosis-regulating proteins account for differences in clinical outcome among patients with early-stage colorectal cancer. EXPERIMENTAL DESIGN: Tissue microarray technology was employed to assay the expression of apoptosis-regulating proteins by immunohistochemistry in 106 archival stage II colorectal cancers, making correlations with disease-specific survival. The influence of microsatellite instability (MSI), tumor location (left versus right side), patient age, and gender was also examined. RESULTS: Elevated expression of several apoptosis regulators significantly correlated with either shorter (cIAP2; TUCAN) or longer (Apaf1; Bcl-2) overall survival in univariate and multivariate analyses. These biomarkers retained prognostic significance when adjusting for MSI, tumor location, patient age, and gender. Moreover, certain combinations of apoptosis biomarkers were highly predictive of death risk from cancer. For example, 97% of patients with favorable tumor phenotype of cIAP2(low) plus TUCAN(low) were alive at 5 years compared with 60% of other patients (P = 0.00003). In contrast, only 37% of patients with adverse biomarkers (Apaf1(low) plus TUCAN(high)) survived compared with 83% of others at 5 years after diagnosis (P< 0.0001). CONCLUSIONS: Immunohistochemical assays directed at detection of certain combinations of apoptosis proteins may provide prognostic information for patients with early-stage colorectal cancer, and therefore could help to identify patients who might benefit from adjuvant chemotherapy or who should be spared it.

Age Factors↗
PubMed2005

Clinical, histological, and immunohistochemical features predicting 1p/19q loss of heterozygosity in oligodendroglial tumors.

To identify a better diagnostic criteria for oligodendroglial tumors, we investigated the clinical, histological, and immunohistochemical features that would be able to predict a 1p/19q loss of heterozygosity (LOH) in these tumors. We performed a PCR-based LOH test with the 1p and 19q microsatellite markers by microdissecting tumor in 56 samples (44 oligodendrogliomas and 12 mixed oligoastrocytomas) of paraffin-embedded tissue. Patients with oligodendroglial tumors with 1p/19q LOH had a statistically significant better prognosis for overall survival. Comparative analysis of several features indicated that the 1p/19q LOH tumors were associated with two histological features, "tumor cellularity" and "perinuclear halo," and low O(6)-methylguanine-DNA-methyltransferase (MGMT) expression and high cytoplasmic glutathione S-transferase pi (GST-pi) expression. In addition, the incidence of 1p/19q LOH was infrequent in the youngest age category (less than 20 years old) studied. Using the new features, we could predict the 1p/19q status of oligodendroglial tumors with greater than 90% accuracy. Therefore, applying these features in clinical practice, would be helpful in clarifying oligodendroglial tumor diagnosis.

Adolescent↗
PubMed2005

Correlation of KIT and platelet-derived growth factor receptor alpha mutations with gene activation and expression profiles in gastrointestinal stromal tumors.

Activating mutations of KIT and platelet-derived growth factor receptor alpha (PDGFRA) are known to be alternative and mutually exclusive genetic events in the development of gastrointestinal stromal tumors (GISTs). We examined the effect of the mutations of these two genes on the gene expression profile of 22 GISTs using the oligonucleotide microarray. Mutations of KIT and PDGFRA were found in 17 cases and three cases, respectively. The remaining two cases had no detectable mutations in either gene. The mutation status of KIT and PDGFRA was directly related to the expression levels of activated KIT and PDGFRA, and was also related to the different expression levels of activated proteins that play key roles in the downstream of the receptor tyrosine kinase III family. To evaluate the impact of mutation status and the importance of the type of mutation in gene expression and clinical features, microarray-derived data from 22 GISTs were interpreted using a principal component analysis (PCA). Three relevant principal component representing mutation of KIT, PDGFRA and chromosome 14q deletion were identified from the interpretation of the oligonucleotide microarray data with PCA. After supervised analysis, there was at least a two fold difference in expression between GISTs with KIT and PDGFRA mutation in 70 genes. Our findings demonstrate that mutations of KIT and PDGFRA affect differential activation and expression of some genes, and can be used for the molecular classification of GISTs.

Adult↗
PubMed2005

Serum withdrawal kills U937 cells by inducing a positive mutual interaction between reactive oxygen species and phosphoinositide 3-kinase.

Reactive oxygen species (ROS) can be generated following cell stimulation and function as intracellular signaling molecules. To determine signaling components involved in ROS induction, human U937 blood cells grown in 10% serum were exposed to serum-free media. It was previously reported that serum withdrawal (SW) killed cells by elevating cellular ROS levels. This study showed that SW activates phosphoinositide 3-kinase (PI3K). PI3K activation was evident after the ROS levels began increasing, and an antioxidant blockade of this increase resulted in PI3K activation suppression. Interestingly, the inhibition of PI3K activity/activation using either its specific inhibitor or dominant-negative mutant attenuated the subsequent additional increase in the ROS levels. These results suggest that SW-induced ROS activate PI3K, which in turn promotes the process leading to ROS accumulation. The present study also revealed that both ROS and PI3K support SW-induced cell death by activating stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK). Overall, it appears that SW triggers a positive mutual interaction between ROS and PI3K, which amplifies signals required for the induction of an SAPK-dependent death pathway.

Catalase↗
PubMed2005

Impaired nonhomologous end-joining in mismatch repair-deficient colon carcinomas.

Frameshift mutations of coding mononucleotide repeat of the hRAD50 gene and formation of the mutant hMRE11 splicing variant are frequent events in tumors with mismatch repair (MMR) deficiency. Both the hRAD50 and hMRE11 proteins form a heterotrimer with the NBS1, and this heterotrimer is involved in the double strand DNA break repair by homologous recombination and nonhomologous end-joining (NHEJ). In order to clarify the role of hRAD50 and hMRE11 gene alterations in MMR-deficient tumors, we analyzed the expression of the hRAD50 and hMRE11 proteins and we evaluated NHEJ in the seven MMR-deficient and five MMR-proficient colon cancer cell lines. Frameshift mutations of the hRAD50 gene were found in five of seven MMR-deficient cell lines, and this was directly related to the decreased expression of hRAD50 mRNA and protein. The mutant hMRE11 splicing variant was found in all of the seven MMR-deficient cell lines, and this was related to the decreased hMRE11 expression in four of the seven MMR-deficient cell lines. MMR-deficient cell lines with decreased hRAD50 and hMRE11 expressions were more sensitive to gamma-irradiation, and these cell lines showed an impaired NHEJ. The impairment of NHEJ was induced after knockdown of hRAD50 and hMRE11 through small interference RNA. Our findings suggest that mutations of hRAD50 and hMRE11 genes in MMR-deficient tumors are related to the defects in NHEJ, and this may result in chromosomal changes during the progression of tumor.

Acid Anhydride Hydrolases↗
PubMed2005

ADP-overexpressing adenovirus elicits enhanced cytopathic effect by induction of apoptosis.

Replication-competent adenoviruses (Ad's) are emerging as a promising new modality for treatment of cancer. Selective replication of viral agents in tumor may lead to improved efficacy over nonreplicating Ad's due to their inherent ability to multiply, lyse, and spread to surrounding cells. We have previously shown that an E1B 55 kDa-deleted adenovirus (YKL-1) exhibits tumor-specific replication and cell lysis, but its cytolytic effects were reduced in comparison to the wild-type adenovirus. To increase the oncolytic potency of YKL-1, we have reintroduced the Ad death protein (ADP) gene under the control of either a CMV or an MLP promoter at the E3 region of YKL-1, generating YKL-cADP and YKL-mADP Ad's, respectively. ADP is an 11.6 kDa protein encoded by the E3 transcription unit, and is required to kill adenovirus-infected cells efficiently. However, to date, the mechanism by which ADP mediates cell death has not been clearly defined. In this study, we report that ADP-overexpressing Ad markedly enhanced cytolytic effect (up to 100-fold) against all tumor cell lines tested, but did not increase cytopathic effect in normal skin fibroblast, BJ. Moreover, plaque size formed by YKL-cADP was substantially larger than that of YKL-1, indicating an enhancement in cell lysis. TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling) assay and Annexin-V/PI double staining indicate that ADP-mediated cytotoxicity was largely driven by apoptosis. Finally, YKL-cADP adenovirus also showed superior antitumor effect than YKL-1 and YKL-mADP in C33A cervical and Hep3B hepatoma xenograft tumor models. Taken together, these lines of evidence demonstrate that the newly generated adenovirus expressing ADP under the CMV promoter induces efficient but tumor-selective cell lysis, which is critical for adding therapeutic value to replicating adenovirus for its use in cancer gene therapy.

Adenoviridae↗