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Kevin J Cullen

Publications and source records attributed to Kevin J Cullen.

6 recordsLinked to original sources
PubMed2006

Cisplatin preferentially binds mitochondrial DNA and voltage-dependent anion channel protein in the mitochondrial membrane of head and neck squamous cell carcinoma: possible role in apoptosis.

PURPOSE: Cisplatin adducts to nuclear DNA (nDNA) are felt to be the molecular lesions that trigger apoptosis, but the mechanism linking nDNA adduct formation and cell death is unclear. Some literature in the last decade has suggested a possible direct effect of cisplatin on mitochondria independent of nDNA interaction. In this study, we define separately the sequelae of cisplatin interactions with nDNA and with mitochondria in head and neck squamous cell carcinoma (HNSCC) cell lines. EXPERIMENTAL DESIGN: Cisplatin binding to mitochondrial DNA (mtDNA) and proteins was analyzed by atomic absorption spectroscopy and other methods. RESULTS: Following 1 hour of exposure to cisplatin, platinum adducts to mtDNA were 300- to 500-fold more abundant than adducts to nDNA; these differences were not due to differences in rates of adduct repair. Whereas HNSCC cell cytoplasts free of nDNA retained the same dose-dependent cisplatin sensitivity as parental cells, HNSCC rho(0) cells free of mtDNA were 4- to 5-fold more resistant to cisplatin than parental cells. Isolated mitochondria released cytochrome c within minutes of exposure to cisplatin, and ultrastructural analysis of intact HNSCC cells by electron microscopy showed marked mitochondrial disruption after 4 hours of cisplatin treatment, whereas the nucleus and other cellular structures remain intact. The very prompt release of cytochrome c from isolated mitochondria implies that apoptosis does not require alteration in mitochondrial gene transcription. Further, cisplatin binds preferentially to mitochondrial membrane proteins, particularly the voltage-dependent anion channel. CONCLUSIONS: Cisplatin binding to nDNA is not necessary for induction of apoptosis in HNSCC, which can result from direct action of cisplatin on mitochondria.

Antineoplastic Agents↗
PubMed2003

Glutathione S-transferase pi amplification is associated with cisplatin resistance in head and neck squamous cell carcinoma cell lines and primary tumors.

PURPOSE: The purpose is to evaluate the association of glutathione S-transferase pi (GST-pi) amplification and cisplatin resistance in head and neck cancer. EXPERIMENTAL DESIGN: An analysis of chromosomal abnormalities in 10 head and neck cancer cell lines by comparative genomic hybridization was performed. GST-pi amplification and expression were evaluated in head and neck cell lines and paraffin-embedded tissue by fluorescence in situ hybridization (FISH) and immunohistochemistry. RESULTS: Changes in the DNA copy number were seen in all 10 cell lines by comparative genomic hybridization. The most frequent chromosomal alterations were: gain at 3q; loss at 3p; gain at 8q; loss of 18q; gain at 20q; loss at 8p; and gain of 11q11-q13. Using FISH, 9 of 10 cell lines showed increased GST-pi copy number. GST-pi amplification was detected in 7 of 10 cell lines. Five were relatively cisplatin resistant, and 2 were relatively cisplatin sensitive (mean IC(50), 11.2 and 2.75 microM). Two relatively cisplatin-sensitive cell lines showed GST-pi gain and another relatively cisplatin-sensitive cell line had predominantly two copies of the gene. In 10 tumor specimens, 4 had two copies of GST-pi. All 4 had a complete response to neoadjuvant chemotherapy, 3 of whom are alive >50 months from treatment compared with 2 patients showing GST-pi amplification. Neither responded to chemotherapy, and both died of disease <9 months from diagnosis. CONCLUSIONS: Using FISH, GST-pi amplification is a common event in head and neck squamous cell carcinoma and may be associated with cisplatin resistance and poor clinical outcomes in head and neck cancer patients treated with cisplatin-based therapy.

Antineoplastic Agents↗
PubMed2003

Inhibition of glutathione synthesis reverses Bcl-2-mediated cisplatin resistance.

Cisplatin is a potent cytotoxic agent that functions as a bivalent electrophile, forming both interstrand and intrastrand DNA cross-links. Cisplatin-mediated DNA damage results in cell cycle arrest and initiation of apoptotic cell death. Increased cellular glutathione concentrations have been closely correlated with cisplatin resistance but do not reduce the extent of cisplatin-DNA adduct formation. One hypothesis to explain the ability of glutathione to inhibit cisplatin cytotoxicity is that glutathione, through its antioxidant function, plays a role in apoptotic regulatory pathways. We tested this hypothesis using MCF-7 breast cancer cells transfected with the apoptotic inhibitor Bcl-2. Bcl-2 overexpression in MCF-7 cells was associated with a nearly 3-fold increase in cellular glutathione levels and with increased resistance to cell death after cisplatin exposure. Treatment of MCF-7 lines with buthionine sulfoximine, an inhibitor of glutathione synthesis, normalized glutathione levels in Bcl-2 and control transfectants and completely abrogated Bcl-2-mediated cisplatin resistance without affecting Bcl-2 expression. Bcl-2 overexpression and up-regulation of glutathione were not associated with a change in either cisplatin-DNA adduct formation or repair over time. These results suggest that Bcl-2-mediated cisplatin resistance in MCF-7 cells is dependent on up-regulation of glutathione production, which contributes to cell survival by mechanisms independent of cisplatin inactivation or inhibition of DNA adduct formation. A similar dependence on glutathione for Bcl-2-mediated inhibition of cisplatin toxicity was confirmed in a second cell line, the lymphocytic precursor FL5.12. Taken together, these data suggest that apoptotic signaling after genotoxic exposure can be inhibited by the antioxidant activity of glutathione. Inhibition of glutathione synthesis or modulation of glutathione stores in tumors that overexpress Bcl-2 may comprise a novel anticancer strategy.

Antineoplastic Agents↗
PubMed2003

Capecitabine induces rapid, sustained response in two patients with extensive oral verrucous carcinoma.

PURPOSE: Oral verrucous carcinoma (VC) has been traditionally treated with surgery or radiation with frequent recurrences and significant morbidity. We describe rapid and dramatic response to oral capecitabine in two patients with advanced refractory VC. EXPERIMENTAL DESIGN: VC is a rare tumor of the oral cavity. It does not metastasize but over time causes morbidity and mortality through local invasion. Radiation and surgery have been the main treatment modalities but are plagued by mutilating effects, recurrences, and possibly malignant degeneration in some cases. To date, no effective chemotherapy regimens have been described in the international literature. The clinical records of two elderly females with extensive oral VC are described. Both patients were prescribed one cycle of capecitabine, 1,000 mg bid for 14 days. Response was documented by photography in one patient. Immunohistochemical evaluation of three 5-fluorouracil metabolizing enzymes on pretreatment biopsies from both patients was also performed. A review of the literature with emphasis on treatment of oral VC is presented in view of our findings. RESULTS: Examination of the oral cavity before treatment revealed extensive involvement with an evenly spreading, exophytic, warty, whitish lesion in both patients. Microscopic examination of H&E-stained slides from biopsies of these lesions confirmed the clinical suspicion of VC. Both patients underwent treatment with oral capecitabine for one cycle (2 weeks on/1 week off) at a reduced dose of 1000 mg, p.o., bid. Both had a dramatic response with near complete resolution of their lesions within 3 weeks of initiating therapy. A durable partial response was documented at 1 year in the first patient and 6 months in the second. Immunohistochemical evaluation of pretreatment biopsies from both patients revealed a high level of expression of thymidine phosphorylase, a key enzyme in the metabolism of capecitabine. CONCLUSIONS: Oral VC is a rare entity with a progressive course over years and limited options in terms of treatment. Preliminary observations in two elderly patients demonstrate that capecitabine, an oral fluoropyrimidine, is well tolerated and may induce rapid, clinically significant response. Although not curative, it may provide a cost-effective alternative for elderly patients with a significant improvement in their quality of life.

Antimetabolites, Antineoplastic↗
PubMed2002

MMP-2 and MMP-9 expression in breast cancer-derived human fibroblasts is differentially regulated by stromal-epithelial interactions.

Tissue remodeling is a key element in the local invasion and metastasis of malignant breast tumors. The degradation of extracellular matrix that is associated with this process is thought to be mediated by a number of Zn2+-dependent matrix metalloproteinases (MMPs). In most cases these enzymes are not produced by the malignant epithelium itself but by adjacent breast stroma, suggesting an important role for cell-cell interactions. We have analyzed Gelatinase A (MMP-2) and Gelatinase B (MMP-9) gene expression in a panel of six breast cancer cell lines and six primary cultures of stromal cells deriving from breast cancer biopsies. With one exception we did not detect MMP-2 or MMP-9 gene expression in any of the established tumor cell lines. Conversely, tumor stroma-derived fibroblasts expressed MMP-2 mRNA. although no MMP-9 mRNA was seen in RNase protection assays. When fibroblasts were cultured in the presence of media conditioned by MCF-7 tumor cells, MMP-2 enzyme production increased but MMP-9 activity remained undetectable. However, when fibroblasts and MCF-7 tumor cells were co-cultured together, MMP-9 was induced. These observations were confirmed by immunocytochemical analysis of co-cultures of MCF-7 and tumor-derived fibroblasts in which MMP-2 and MMP-9 protein expression was confined to stromal cells adjacent to MCF-7 tumor cells. No MMP-2 or MMP-9 staining was detected in monocultures of the two respective cell types. We conclude that MMP-2 expression is present in the stroma of malignant tumors and is increased by paracrine stimulation mediated by soluble factors. In contrast, MMP-9 expression tumor-derived fibroblasts requires direct contact with malignant tumor epithelium.

Breast Neoplasms↗