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Biomedical subjects

R R Weichselbaum

Publications and source records attributed to R R Weichselbaum.

At least 163 records · Page 9Linked to original sources
PubMed1992

The interaction of 5-fluorouracil, hydroxyurea, and radiation in two human head and neck cancer cell lines.

We have investigated the effects of 5-fluorouracil (5-FU) and hydroxyurea (HU) with radiation on two human head and neck squamous carcinoma cell lines. SQ-20B has a D0 of 239 cGy and an S phase fraction of 37%, while SQ-38 has a D0 of 146 cGy and an S phase fraction of 31%. For SQ-20B the surviving fraction at 100 cGy was significantly reduced (p < 0.05) when cells were exposed to HU or to 5-FU or both chemotherapy agents together with radiation. No significant effect was seen for SQ-38 with either chemotherapy agent alone or in combination with radiation as compared with radiation alone. Therefore, additive cytotoxicity between 5-FU and HU and radiotherapy was observed only in a head and neck cancer cell line with a higher D0 and a higher S phase fraction.

Cell Survival↗
PubMed1992

Concomitant chemoradiotherapy with cisplatin, 5-fluorouracil and hydroxyurea in poor-prognosis head and neck cancer.

Based on encouraging results with 5-fluorouracil (5-FU), hydroxyurea, and concomitant radiotherapy in patients with advanced or recurrent head and neck cancer, an attempt was made to modulate the regimen by the addition of cisplatin as a third active agent. A cohort of 26 patients with head and neck cancer of all histologies were entered into a broad phase I study investigating simultaneous radiation therapy, 5-FU (with or without leucovorin), HU, and infusional cisplatin administered on an alternate-week schedule. Eleven patients (group 1) had failed prior curative local therapy and 15 patients (group 2) were considered to have a poor prognosis with standard therapy. The median follow-up was 30 months. The response rate for all evaluable patients was 82% (14/17), and the complete response rate was 65% (11/17). Patients in group 1 demonstrated a high failure rate (9/11), while few group 2 patients failed after treatment (2/15). The median time to progression was 4.4 months in group 1 and has not been reached in group 2. Patients in group 1 failed locally (7/11), while no local failures were observed in group 2. Acute and cumulative hematologic toxicity was encountered at all dose levels and schedules tested and prevented escalation of the cisplatin dose beyond the desired level of 100 mg/m2 per months. Mucositis was a second significant toxicity in patients with head and neck cancer and was more pronounced during cycles containing leucovorin. A detailed analysis of survival, time to progression, and site of failure is presented.

Adult↗
PubMed1992

Molecular targets to overcome radioresistance.

Our laboratory has cultured cells from 23 patients with head and neck carcinoma and 13 patients with soft tissue sarcoma. The data suggest that, in some patients, inherent tumor cell radioresistance contributes to radiotherapy failure. This paper examines possible mechanisms that lead to increased cell survival following radiation exposure, and their potential as targets to overcome the radioresistant patient population.

Antineoplastic Agents↗
PubMed1992

Perspectives on combination chemotherapy with concomitant radiotherapy for poor-prognosis head and neck cancer.

Concomitant chemoradiotherapy has resulted in small increases in disease-free or overall survival for patients with advanced head and neck cancer when single-agent chemotherapy is used. To increase the efficacy of this approach, combination chemotherapy also has been explored. In this setting, acute toxicities are frequently increased, necessitating interruption or protraction of radiotherapy. Despite this fact, pilot trials using 5-fluorouracil-based chemotherapy have indicated high response and encouraging survival rates. Some of these trials will be reviewed, with a focus on studies with 5-fluorouracil, hydroxyurea, and cisplatin conducted at the University of Chicago.

Adult↗
PubMed1992

Inhibition of protein kinases sensitizes human tumor cells to ionizing radiation.

Protein kinase C (PKC) is activated rapidly and transiently following ionizing radiation exposure and is postulated to activate downstream nuclear signal transducers. Inhibition of this enzyme attenuates radiation-mediated expression of the c-jun and Egr-1/zif-268 genes which are associated with cellular proliferation. To investigate further the role of PKC in the radiation response of human tumor cell lines, two human squamous cell carcinoma cell lines, SQ-20B and JSQ-3, were exposed to graded doses of X rays in the presence of staurosporine, sangivamycin, or H7, all PKC inhibitors. The protein kinase inhibitors staurosporine and sangivamycin produced dose-dependent cytotoxicity in cells of the SQ-20B and JSQ-3 cell lines while H7 did not. Nontoxic concentrations of sangivamycin (10 nM) and staurosporine (1 nM), added to cell cultures from 1 to 7 h before X irradiation, enhanced cell killing by radiation in both cell lines. Maximal sensitization of killing occurred when inhibitors were added 1 h prior to irradiation. The enhanced radiation-induced cell killing was not due to any measurable alteration in the induction or rejoining of DNA single- or double-strand breaks as determined by alkaline and neutral filter elution assays. These data suggest that protein kinase activity is important for cell survival following radiation exposure, although the specific role of PKC in radiation responses is unknown.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1992

Expression of the polymorphic human DNA repair gene XRCC1 does not correlate with radiosensitivity in the cells of human head and neck tumor cell lines.

The human X-ray repair cross-complementing gene 1 (XRCC1) is highly polymorphic in the cells of human head and neck squamous cell carcinoma lines and in a variety of other human cell lines. We describe six patterns seen in Southern analysis of EcoRI-digested genomic DNA. Levels of XRCC1 mRNA vary in cells of human head and neck cell lines as seen in northern blots. Expression of this gene in cell culture does not correlate with radiobiological parameters, clinical outcome, or the DNA restriction fragment length polymorphisms.

Blotting, Northern↗
PubMed1992

Hydroxyurea with concomitant radiotherapy for locally advanced head and neck cancer.

Hydroxyurea is an active single agent in squamous cell cancer of the head and neck. It has been used clinically, most frequently as a radiation-enhancing agent with concomitant radiotherapy. Pilot trials testing hydroxyurea in this setting reported encouraging results. Two randomized trials have been conducted with inconclusive results, possibly relating to study cohort size and short period of follow-up. More recently, hydroxyurea has been investigated with 5-fluorouracil and concomitant radiotherapy. A sound theoretic rationale can be made for this approach and data derived from a phase I/II study are presented. These support the further investigation of this regimen.

Administration, Oral↗
PubMed1991

p53 gene mutations and abnormal retinoblastoma protein in radiation-induced human sarcomas.

The potentially carcinogenic effect of therapeutic irradiation has been recognized for many years. Second malignancies, usually sarcomas, are known to arise within or at the edge of radiation fields after a period of several years after the initial radiation exposure. We analyzed tumor cells derived from seven radiation-induced tumors for abnormalities in tumor suppressor genes p53 and retinoblastoma at the DNA sequence and/or protein level. p53 mutations were detected by exon-specific polymerase chain reaction amplification and single-strand conformation polymorphism analysis of exons 5-8 followed by direct genomic sequencing of those tumors exhibiting a variant pattern. The p53 gene was abnormal in three of six sarcomas studied. Retinoblastoma gene analysis was performed by Western immunoblot; retinoblastoma protein was under-phosphorylated in three of seven tumors and absent in one other. In all, six of seven radiation-induced human tumors have abnormalities of one or both suppressor genes. Inactivation of tumor suppressor genes by ionizing radiation may contribute to radiation carcinogenesis.

Amino Acid Sequence↗
PubMed1991

Tumor necrosis factor gene expression is mediated by protein kinase C following activation by ionizing radiation.

Tumor necrosis factor (TNF) production following X-irradiation has been implicated in the biological response to ionizing radiation. Protein kinase C (PKC) is suggested to participate in TNF transcriptional induction and X-ray-mediated gene expression. We therefore studied radiation-mediated TNF expression in HL-60 cells with diminished PKC activity produced by either pretreatment with protein kinase inhibitors or prolonged 12-O-tetradecanoylphorbol-13-acetate treatment. Both treatments resulted in attenuation of radiation-mediated TNF induction. Consistent with these results, we found no detectable induction of TNF expression following X-irradiation in the HL-60 variant deficient in PKC-mediated signal transduction. The rapid activation of PKC following gamma-irradiation was established using an in vitro assay measuring phosphorylation of a PKC specific substrate. A 4.5-fold increase in PKC activity occurred 15 to 30 s following irradiation, which declined to baseline at 60 s. Two-dimensional gel electrophoresis of phosphoproteins extracted from irradiated cells demonstrated in vivo phosphorylation of the PKC specific substrate Mr 80,000 protein at 45 s following X-irradiation. These findings indicate that signal transduction via the PKC pathway is required for the induction of TNF gene expression by ionizing radiation.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1991

Measurement of bioreduction rates of cells with distinct responses to ionizing radiation and cisplatin.

A low frequency electron paramagnetic resonance (EPR) spectrometer has been used to measure the bioreduction rate of an exogenously added nitroxide free radical species. Measurements have been made in a well controlled, in vitro system using an X-ray and cisplatin sensitive Chinese hamster ovary (CHO) cell line, xrs-5, and partial revertants which display wild-type levels of sensitivity to X-rays but retain xrs-5 levels of cisplatin sensitivity. The xrs-5 cells reduce this radical species at a rate which is approx. 50% that of the wild-type CHO cell line, K1. The partial revertants maintain this defect in bioreduction despite their decrease in radiosensitivity. However, the bioreduction rate observed in these cells correlates with their sensitivity to the chemotherapeutic drug cisplatin. Low frequency EPR allows measurements and imaging of living tissue and may be of value as a predictive assay of human tumor response to chemotherapy.

Animals↗
PubMed1991

Biological consequences of gene regulation after ionizing radiation exposure.

Ionizing radiation is a ubiquitous environmental mutagen and carcinogen widely used in cancer therapy. However, little is known about the induction of cellular signaling events and specific gene expression after radiation exposure. We review the accumulating evidence that ionizing radiation induces signal transduction pathways involving activation of protein kinase C and a program of genetic events that may contribute to the biological effects of x rays.

Base Sequence↗
PubMed1991

Protein kinase C mediates x-ray inducibility of nuclear signal transducers EGR1 and JUN.

The cellular response to ionizing radiation includes growth arrest and DNA repair followed by proliferation. Induction of immediate early response genes may participate in signal transduction preceding these phenotypic responses. We analyzed mRNA expression for different classes of immediate early genes (JUN, EGR1, and FOS) after cellular x-irradiation. Increased expression of the EGR1 and JUN genes was observed within 0.5-3 hr following x-ray exposure. Preincubation with cycloheximide was associated with superinduction of JUN and EGR1 in x-irradiated cells. Inhibition of protein kinase C activity by prolonged stimulation with phorbol 12-myristate 13-acetate or the protein kinase inhibitor H7 prior to irradiation attenuated the increase in EGR1 and JUN transcripts. FOS expression was not coregulated with that of EGR1 following x-irradiation, suggesting a distinct regulatory pathway of this gene as compared with its regulation following serum and phorbol ester. These data implicate the EGR1 and JUN proteins as signal transducers during the cellular response to radiation injury and suggest that this effect is mediated in part by a protein kinase C-dependent pathway.

Cell Line↗
PubMed1991

Increased glutathione peroxidase activity in a human sarcoma cell line with inherent doxorubicin resistance.

Several mechanisms of drug resistance have been defined using cell lines selected for resistance in vitro. However, the relevance of these to tumor cell resistance in vivo remains unclear. We established tumor cell lines from biopsies of human sarcomas before and after doxorubicin therapy. One pretreatment sarcoma line, STSAR90, was 6-fold less sensitive to doxorubicin than was a normal fibroblast line, AG1522. The sensitivities of six other sarcoma lines were similar to that of AG1522. STSAR90 cells did not overexpress P-glycoprotein mRNA, by Northern analysis with the pCHP1 complementary DNA fragment. Photoaffinity labeling with the vinblastine analogue N-(p-azido-3-125I-salicyl)-N'-beta-aminoethylvindesine did not show increased P-glycoprotein concentrations. Accumulation of [3H]daunomycin was not decreased in STSAR90 compared with a less resistant sarcoma line, STSAR11, nor was the doxorubicin sensitivity of STSAR90 increased by coincubation with verapamil. Glutathione levels were twice as high in STSAR90 as in STSAR11, and glutathione peroxidase activity was 3.5- to 6-fold higher. This was due mostly to an increase in selenium-dependent peroxidase activity. After exposure to doxorubicin, STSAR90 cells formed only half as much measurable hydroxyl radical as STSAR11, as detected by electron spin resonance spectrometry. Doxorubicin sensitivity was increased in STSAR90 cells when intracellular glutathione levels were reduced by buthionine sulfoximine. These results indicate that multidrug resistance due to P-glycoprotein-mediated drug efflux is not the only mechanism of doxorubicin resistance that occurs in sarcomas and that glutathione peroxidase-dependent detoxification of doxorubicin-induced oxygen radicals may contribute to clinical doxorubicin resistance.

Adolescent↗
PubMed1991

Two prostate carcinoma cell lines demonstrate abnormalities in tumor suppressor genes.

Two prostate carcinoma cell lines, DU-145 and PC-3, were examined for abnormalities in the retinoblastoma (Rb) and the p53 putative tumor suppressor genes. We found an abnormal Rb gene product in DU-145 using Western blot analysis. Polymerase chain reaction amplification followed by direct DNA sequencing demonstrated a base substitution mutation that generates a stop codon in exon 21. On Northern, Southern, and Western blot analysis, the p53 gene and its product appear to be normal in DU-145. PC-3, however, failed to demonstrate expression of either the p53 transcript on Northern blot analysis or the p53 protein on Western blot analysis, while the Rb gene products appeared to be normal on both Northern and Western blot analysis. This work extends the correlation between abnormal expression of putative tumor suppressor genes and human malignancies.

Base Sequence↗
PubMed1991

Variation in radiation sensitivity during the cell cycle of two human squamous cell carcinomas.

Changes in the radiation age response are described in two cell lines derived from human squamous cell carcinomas. A radioresistant tumor cell line, JSQ-3, has a DO of 240 cGy and is polyploid with a DNA content of 2.68. A relatively radiosensitive tumor cell line, SCC-61, has a DO of 126 cGy and has a DNA index of 1.16. Tumor cells were separated and synchronized by centrifugal elutriation; flow cytometry was used to determine cell-cycle parameters and relative synchrony. The radioresistant cell line, JSQ-3B, was found to have twice the number of cells in S-phase than the more sensitive cell line (28% and 13% for JSQ-3B and SCC-61B, respectively). Both cell lines, despite differences in intrinsic radiosensitivity, were most resistant during S-phase (DOs of 258 and 157 cGy for JSQ-3B and SCC-61B, respectively) and were maximally sensitive during G1 (DOs of 193 and 95 cGy for JSQ-3B and SCC-61B, respectively). Clinical implications of our findings are discussed.

Carcinoma, Squamous Cell↗
PubMed1991

Curative radiotherapy following chemotherapy for invasive bladder carcinoma (a preliminary report).

Twenty-five patients with invasive transitional cell carcinoma of the bladder (Stage T2, T3, T4) received combined modality therapy using four cycles of methotrexate, vinblastine, adriamycin, and cisplatin (MVAC) chemotherapy followed by surgery or radiation therapy (RT). Sixteen patients had complete (N = 8) or partial (N = 8) response to MVAC. Curative RT was delivered to 11 responders with T2 or T3 disease and to 2 patients with T4 disease. All 11 with T2 and T3 disease are currently alive, 7 with normal bladder function. The two with T4 disease are dead of disease. Three patients required salvage cystectomy for local recurrence and one patient had cystectomy for bladder stones. Follow-up ranged from 11 to 50 months with a median of 31 months. No late chemo-radiotherapy treatment-related complications to the intestines or in bladder function (other than one bladder stone formation) occurred. These preliminary results are encouraging and warrant further evaluation of this innovative approach in treating invasive carcinoma of the bladder. T2 and T3 patients with a complete or partial response to MVAC may be excellent candidates for a bladder-sparing treatment.

Adult↗
PubMed1991

Mechanisms of X-ray-mediated protooncogene c-jun expression in radiation-induced human sarcoma cell lines.

c-jun is a protooncogene associated with neoplastic transformation and is transcriptionally induced by ionizing radiation. To examine the possible mechanisms of radiation-induced c-jun transcription, we analyzed RNA from human tumor cell lines RIT-3 and STSAR-5 following x-irradiation in the presence of protein kinase inhibitors, or the absence of serum and calcium. Protooncogene c-jun expression increased several fold following irradiation of these radiation-induced human sarcoma cell lines. The expression of c-jun was not altered following irradiation in conditioned medium containing serum as compared to that of cells in serum free medium. Depletion of PKC by prolonged TPA treatment resulted in inhibition of c-jun expression. In addition, nonspecific protein kinase inhibitors, staurosporin and H7 attenuated c-jun expression, whereas the analogue of ATP (sangivamycin) did not. Furthermore, the selective inhibitor of cAMP dependent protein kinase HA 1004 did not alter radiation-mediated c-jun induction. These data indicate that ionizing radiation exposure results in c-jun induction which is dependent upon the activation of PKC. Protein kinase C activation and the subsequent expression of the protooncogene c-jun by ionizing radiation may further define the molecular mechanisms of radiation-induced neoplastic transformation.

Enzyme Activation↗