Relationship of glutathione and glutathione-S-transferase to cisplatin sensitivity in human head and neck squamous carcinoma cell lines

[Accumulation Mechanism of 2-Nitroimidazole-based Hypoxia Imaging Probes Revealed by Imaging Mass Spectrometry]

Hypoxia in tumor tissues plays a pivotal role in tumor progression and angiogenesis, and is associated with cancer therapeutic resistance. For the diagnosis of hypoxia, non-invasive imaging techniques, especially positron emission tomography (PET) with 2-nitroimidazole-based probes, are used, since 2-nitroimidazole-based probes are considered to undergo reductive metabolism on their 2-nitroimidazole moiety and become trapped in hypoxic cells. However, the detailed mechanism of their accumulation remains unclear because of the difficulty in estimating the metabolites by radioisotopic analysis. Imaging mass spectrometry (IMS) can distinguish the distribution patterns of the drug and its metabolites. To clarify the accumulation mechanism of 2-nitroimidazole-based probes in hypoxic cells, we evaluated [¹⁸F]fluoromisonidazole (FMISO), a 2-nitroimidazole-based PET probe, in combination with radioisotopic analysis and IMS. We found that the glutathione conjugate of reduced FMISO (amino-FMISO-GS) was the main FMISO metabolite, and was specifically distributed in the hypoxic regions of tumors. The same phenomenon was observed when we examined another 2-nitroimidazole-based probe, pimonidazole. The in vitro cellular uptake study revealed that FMISO accumulation in hypoxic cells depends on the cell type. In those cells exhibiting higher FMISO uptake, the reactive glutathione level and enzyme (glutathione S-transferase; GST) activity catalyzing the glutathione conjugation reaction was significantly higher, whereas the expression level of the efflux transporter (multidrug resistance-associated protein 1; MRP1) was significantly lower. Our study suggests that 2-nitroimidazole-based probes accumulate in hypoxic cells via glutathione conjugation following reductive metabolism, which depends not only on the glutathione conjugation capacity of the cells but also on hypoxic conditions.

FMISO accumulation in tumor is dependent on glutathione conjugation capacity in addition to hypoxic state

OBJECTIVE

¹⁸F-fluoromisonidazole (FMISO), a well-known PET imaging probe for diagnosis of hypoxia, is believed to accumulate in hypoxic cells via covalent binding with macromolecules after reduction of the nitro group. Previously, we showed the majority of ¹⁸F-FMISO was incorporated into low-molecular-weight metabolites in hypoxic tumors, and the glutathione conjugate of reduced FMISO (amino-FMISO-GS) distributed in the tumor hypoxic regions as revealed by imaging mass spectrometry (IMS). The present study was conducted to clarify whether FMISO is metabolized to amino-FMISO-GS within tumor cells and how amino-FMISO-GS contributes to FMISO accumulation in hypoxic cells. We also evaluated the relationship between FMISO accumulation and the glutathione conjugation-related factors in the cells.

METHODS

Tumor cells (FaDu, LOVO, and T24) were treated with ¹⁸F-FMISO and incubated under normoxic or hypoxic conditions for 4 h. The FMISO metabolites were analyzed with LC-ESI-MS. Several glutathione conjugation-related factors of tumor cells were evaluated in vitro. FaDu tumor-bearing mice were intravenously injected with ¹⁸F-FMISO and the tumors were excised at 4 h post-injection. Autoradiography, IMS and histologic studies were performed.

RESULTS

Amino-FMISO-GS was the main contributor to FMISO incorporated in hypoxic FaDu cells in vitro and in vivo. Total FMISO uptake levels and amino-FMISO-GS levels were highest in FaDu, followed by LOVO, and then T24 (total uptake: 0.851 ± 0.009 (FaDu), 0.617 ± 0.021 (LOVO) and 0.167 ± 0.006 (T24) % dose/mg protein; amino-FMISO-GS: 0.502 ± 0.035 (FaDu), 0.158 ± 0.013 (LOVO), and 0.007 ± 0.001 (T24) % dose/mg protein). The glutathione level of FaDu was significantly higher than those of LOVO and T24. The enzyme activity of glutathione-S-transferase catalyzing the glutathione conjugation reaction in FaDu was similar levels to that in LOVO, and was higher than that in T24. Quantitative RT-PCR analysis revealed that the expression levels of efflux transporters of the glutathione conjugate (multidrug resistance-associated protein 1) were lowest in FaDu, followed by LOVO, and then T24.

CONCLUSIONS

FMISO accumulates in hypoxic cells through reductive metabolism followed by glutathione conjugation. We illustrated the possibility that increased production and decreased excretion of amino-FMISO-GS contribute to FMISO accumulation in tumor cells under hypoxic conditions.

Nuclear localization of glutamate-cysteine ligase is associated with proliferation in head and neck squamous cell carcinoma

Glutathione (GSH) is the keystone of the cellular response toward oxidative stress. Elevated GSH content correlates with increased resistance to chemotherapy and radiotherapy of head and neck (HN) tumors. The purpose of the present cross-sectional study was to evaluate whether the expression of glutamate-cysteine ligase (GCL) accounts for the increased GSH availability observed in HN squamous cell carcinoma (SCC). For that purpose, the messenger (m)RNA levels of the modifier (M) and catalytic (C) subunits of GCL and its putative regulators (namely, nuclear factor erythroid 2-related factor 2, heme oxygenase-1 and nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha) were monitored in 35 surgical resections of untreated HNSCC. The localization of GCLM was evaluated using in situ hybridization and immunohistochemistry. GCLM expression was significantly increased in tumor samples, compared with normal mucosa, both at the mRNA and protein level (P=0.029), but the pathway of GCLM activation remains to be elucidated. Protein expression of GCLM was detected in the cytoplasm and nucleus. GCLM and the proliferation marker Ki-67 displayed a similar distribution, being both mainly expressed at the periphery of tumor lobules. The present study reported increased expression of GCL and the rate-limiting enzyme of GSH synthesis, within HNSCC. The nuclear localization of GCLM and the concomitant expression of Ki-67 suggested that the localization of GSH synthesis contributes to the protection against oxidative stress within hotspots of cell proliferation.

Trichosanthes dioica root extract induces tumor proliferation and attenuation of antioxidant system in albino mice bearing Ehrlich ascites carcinoma

Trichosanthes dioica Roxb. (Cucurbitaceae), called pointed gourd in English, is a dioecious climber grown widely in the Indian subcontinent. The present study assessed the influence of treatment of hydroalcoholic extract of Trichosanthes dioica root (TDA) on Ehrlich ascites carcinoma (EAC) in Swiss albino mice with effects on antioxidant systems. Twenty-four hours after intraperitoneal inoculation of tumor (EAC) cells in mice, TDA was administered at 25 and 50 mg/kg for 8 consecutive days. On the 9(th) day, half of the mice were sacrificed for estimation of tumor proliferation, hematological, and hepatic antioxidative parameters. The rest were kept for assessment of survival parameters. TDA exhibited dose dependent and significant increase in tumor weight, tumor volume, packed cell volume and viable cells and reduced non-viable cells and life span of EAC bearing animals. Hematological parameters were significantly worsened in TDA-treated mice. TDA treatment significantly aggravated the hepatic antioxidative parameters. The present study demonstrated that T. dioica root possessed tumor promoting activity in EAC bearing albino mice, plausibly mediated by attenuation of endogenous antioxidant systems.

Antitumor efficacy and amelioration of oxidative stress by Trichosanthes dioica root against Ehrlich ascites carcinoma in mice

CONTEXT

Trichosanthes dioica Roxb. (Cucurbitaceae) is a dioecious climber, traditionally used in India for several medicinal purposes.

OBJECTIVE

The present study assessed the hydroalcoholic extract of T. dioica root (TDA) for antitumor effect and antioxidant influence against Ehrlich ascites carcinoma (EAC) in Swiss albino mice.

METHODS

Twenty four hours after intraperitoneal inoculation of tumor (EAC) cells in mice, TDA was administered at 5 and 10 mg/kg body weight daily for 9 consecutive days. On the 10th day, half of the mice were sacrificed for estimation of tumor proliferation, hematological, and liver antioxidant parameters viz. lipid peroxidation, reduced glutathione (GSH), glutathione S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT); and the rest were kept alive for assessment of increase in life span. The antitumor effect of TDA was assessed by evaluating tumor weight, tumor volume, packed cell volume, viable and non-viable tumor cell counts, median survival time and percentage increase in life span of EAC bearing mice.

RESULTS AND DISCUSSION

TDA exhibited dose dependent and significant (p < 0.001) decrease in tumor weight, tumor volume, packed cell volume and viable cell count and extended the life span of EAC bearing hosts. Hematological profiles were significantly (p < 0.001) restored near to normal in TDA treated mice as compared to EAC control. TDA treatment significantly (p < 0.001) modulated the aforesaid liver antioxidant parameters as compared to EAC control.

CONCLUSION

The present study demonstrated that TDA possessed promising antitumor efficacy in mice, plausibly mediated by amelioration of oxidative stress by multiple mechanisms.

The Association Between Polymorphisms in Glutathione S-Transferase (GSTM1andGSTT1) and Lung Cancer Outcome

BACKGROUND

Polymorphisms in the glutathione S-transferase (GST) family may be associated with increased risk of lung cancer, somatic changes in lung tumour tissue, and survival. We evaluated survival according to GST polymorphism in lung cancer patients.

METHODS

We studied DNA polymorphisms of 81 primary lung cancer patients at 2 glutathione-related loci: GSTM1, and GSTT1 that encode glutathione S-transferase-mu, and glutathione S-transferase- square. The presences of the GSTM1 and GSTT1 genes were assayed by PCR. Kaplan-Meier with log rank tests, and Cox regression models were applied in the analysis.

RESULTS

The median age of 75 males and 6 females was 60 years. Median survival of the whole population was 8 months. In the first presentation, none of the patients with GSTT1 null genotype but 30 percent of the patients with GSTT1-positive genotype had liver metastasis (p < 0.01) but GSTT1 genotype was not associated with survival. Sputum (p < 0.01) was more common in patients with GSTM1 null genotype. Subjects with the GSTM1-null genotype had shorter survival. Using a Cox proportional hazard model, GSTM1, tumor (T) factor and thoracic irradiation status were identified as independent prognostic factors.

CONCLUSIONS

Our preliminary results showed that GSTM1-null genotype was associated with shorter survival.

Prediction of chemosensitivity using multigene analysis in head and neck squamous cell carcinoma

AIMS

The main purpose of the current study was to find predictive biomarkers that can be routinely used for the response to chemotherapy in head and neck squamous cell carcinoma (HNSCC).

METHODS

From this standpoint, we selected the histoculture drug response assay (HDRA) to assess in vitro chemosensitivity, and real-time reverse transcription polymerase chain reaction to investigate the gene expression profile of individual tumors as available predictive biomarkers. Using both surgery and biopsy specimens, we analyzed their gene expression profiles using the 18 markers that we thought were likely predictors of the response to anti-cancer agents.

RESULTS

Statistically significant associations were found between 5-fluorouracil (5-FU) sensitivity in HDRA and HER-2 mRNA expression level (p = 0.0030). Moreover, HER-2 expression was significantly associated with cisplatin sensitivity (p = 0.0089). Cisplatin sensitivity in HDRA was also demonstrated to have a significant association with epidermal growth factor receptor (EGFR) expression in which the group with cisplatin resistance tended to have a higher expression level than the sensitive group (p = 0.0385).

CONCLUSION

HER-2 and EGFR may be possible reliable predictive biomarkers for anti-cancer therapy, and might help in the decision-making process for individual patients with HNSCC.

Role of the Glutathione Metabolic Pathway in Lung Cancer Treatment and Prognosis: A Review

Inherent and acquired drug resistance is a cause of chemotherapy failure, and pharmacogenomic studies have begun to define gene variations responsible for varied drug metabolism, which influences drug efficacy. Platinum-based compounds are the most commonly used chemotherapeutic agents in the treatment of advanced stage lung cancer patients, and the glutathione metabolic pathway is directly involved in the detoxification or inactivation of platinum drugs. Consequently, genotypes corresponding to higher drug inactivation enzyme activity may predict poor treatment outcome. Available evidence is consistent with this hypothesis, although a definitive role for glutathione system genes in lung cancer prognosis needs to be elucidated. We present evidence supporting a role of the glutathione system in acquired and inherited drug resistance and/or adverse effects through the impact of either drug detoxification or drug inactivation, thus adversely effecting lung cancer treatment outcome. The potential application of glutathione system polymorphic genetic markers in identifying patients who may respond favorably, selecting effective antitumor drugs, and balancing drug efficacy and toxicity are discussed.

Protective role of Egyptian propolis against tumor in mice

BACKGROUND

Propolis has numerous biologic activities including antibiotic, antifungal, antiviral and anti-inflammatory properties. The present work is aimed to study the effect of crude Egyptian propolis on tumor in mice induced by Ehrlich ascitis carcinoma (EAC) cell line.

RESULTS

The administration of propolis (160 mg/kg body weight), by gastric intubation 2 h before the intraperitoneal injection of EAC, effectively inhibited tumor growth and the proliferation of EAC. The tumor volume was markedly reduced from 7+/-0.9 ml in EAC-infected mice to 1.6+/-0.95 ml in propolis-treated mice. Also, the lipid peroxide level which was 13.3+/-1.24 nmol malodialdehyde (MDA)/mg protein in EAC infected mice was significantly decreased to 3.3+/-2.1 nmol MDA/mg protein. Reduced glutathione (GSH) and glutathione S-transferase (GST) concentrations were markedly increased in propolis-treated mice. This effect was associated with inhibition of cell cycle progression and induction of apoptosis. Administration of propolis 2 h before injection of EAC arrested cells in G0/G1 phase and resulted in a decrease in the viability, DNA, total RNA and protein level of tumor cells.

CONCLUSIONS

Crude Egyptian propolis has a strong inhibitory activity against tumors. The anti-tumor mechanism may be mediated by preventing oxidative damage and induction of apoptosis.

Genetic determinants of lung cancer short-term survival: the role of glutathione-related genes

PURPOSE

Survival of lung cancer patients has been dismal. Glutathione enzymes are directly involved in the metabolism of platinum compounds, a group of important chemotherapeutic drugs in cancer treatment. We tested the hypothesis that genes encoding glutathione enzymes may predict lung cancer short-term survival.

METHODS

We studied DNA polymorphisms of 250 primary lung cancer patients at four glutathione-related loci: GSTP1, GSTM1, GSTT1 and gamma-GCS that encode glutathione-S-transferase-pi, glutathione-S-transferase-mu, glutathione-S-transferase-theta, and gamma-glutamylcysteine synthetase, respectively. Pearson's chi(2)-square tests, Kaplan-Meier survival curves, log rank tests, and Cox regression models were applied in the analysis.

RESULTS

There were 150 (60%) men and 100 (40%) women in this study. Seventeen percent of the patients had never smoked cigarettes, and 61% had stopped smoking at least 6 months prior to their lung cancer diagnosis. Among never smokers, those with null (N) or low (L) genotype experienced a better 1-year-survival rate than those with a positive (P) or high (H) genotype. Patients with P or H at two loci (PP or PH) were compared with patients with N or L at one or both loci (other). Among never smokers, 1-year-survival rates were 60-78% for patients with PP or PH genotypes compared with 89-100% for other types. The survival advantage was greater among advanced-stage patients who were NL or NN than low-stage patients. Similar results were not observed among smokers.

CONCLUSIONS

Glutathione-related genes may determine lung cancer survival. Our results, if confirmed, would suggest new directions to enhance cancer treatment, and provide easily measurable markers for clinicians to plan patient-specific therapy.

Effect of purified allicin, the major ingredient of freshly crushed garlic, on cancer cell proliferation

The diverse health benefit effects of garlic include its anticancer activity. However, very little is known about such activity of isolated garlic compounds, among which allicin (the major ingredient of crushed garlic) has been the least studied. The aim of this work was to determine whether pure allicin exhibits the antiproliferative effect reported for garlic in in vitro models. Allicin, but not its precursor alliin, inhibited proliferation of human mammary (MCF-7), endometrial (Ishikawa), and colon (HT-29) cancer cells (50% inhibitory concentration = 10-25 microM). Two of three tested primary lines of human fibroblasts displayed a similar response to allicin (50% inhibitory concentration = 16-40 microM), whereas the third line was almost unaffected by this compound. The pure allicin and water extract of garlic powder with equivalent allicin concentrations displayed a similar potency, suggesting that allicin is responsible for the antiproliferative effect of the extract. The growth inhibition was accompanied by accumulation of cells in the G0/G1 and G2/M phases of the cell cycle (MCF-7 cells) and not by a significant increase in cell death. Allicin caused a transient drop in the intracellular glutathione (GSH) level, the magnitude and kinetics of which significantly varied depending on cell type. The extent of the decrease in GSH levels correlated well (r = 0.75) with the growth inhibitory activity of allicin. On the basis of these findings, we suggest that allicin plays a major role in the antiproliferative effect of water-soluble garlic preparations and that this effect may be attributed to the ability of allicin to transiently deplete the intracellular GSH level.

Is glutathione-S-transferase-pi expression a reliable predictor of chemoradiation response in cancer of the head and neck?

PURPOSE

Concurrent radiation and chemotherapy is being evaluated as an alternative treatment to surgery for patients with advanced squamous cell carcinoma of the head and neck, because organ preservation maybe possible without compromising survival. However, the response to concurrent chemoradiation treatment varies from patient to patient, and there is currently no available molecular predictor of response for this particular treatment modality. There is some evidence to indicate that glutathione S-transferase-pi (GST-pi), which is one of the drug detoxifying enzymes, may decrease the effectiveness of platinum-based chemotherapy in the treatment of a variety of tumor types. This study was performed to investigate whether GST-pi expression was correlated with response to concurrent chemotherapy and radiotherapy in patients with advanced squamous cell carcinoma of the head and neck.

MATERIALS AND METHODS

Diagnostic biopsy specimens of 36 patients who underwent concurrent chemoradiotherapy for the treatment of advanced squamous cell carcinoma of the head and neck were examined for GST-pi expression by using immunohistochemistry with polyclonal antihuman GST-pi antibodies. GST-pi expression scores were compared among responders and nonresponders.

RESULTS

Although the staining rate with antiGST-pi was slightly lower in the responder group in comparison with the nonresponders (82% vs 100%), the difference was not statistically significant.

CONCLUSION

GST-pi expression is unlikely to be a valuable predictor of response to concurrent chemotherapy and radiation treatment in patients with advanced squamous cell carcinoma of the head and neck.

Molecular biomarkers in HNSCC: prognostic and therapeutic implications

The prognosis of squamous cell carcinoma of head and neck (HNSCC) is influenced by many factors, such as performance status, TNM staging and pathological grading of differentiation. However, these factors are not sufficient for predicting outcome. Therefore, recent research has focused on the identification of molecular biomarkers. These markers help to stage patients in more meaningful prognostic groups and identify high-risk patients who may benefit from a more aggressive treatment approach. They also identify patients who are resistant to radiotherapy or chemotherapy, potentially avoiding the morbidity and cost of ineffective therapies. They can also identify patients with a high risk of recurrence who may benefit from chemoprevention. Finally, these markers may serve as targets for novel therapies, which would eventually change the outcome of HNSCC.

UV reflectance spectroscopy probes DNA and protein changes in human breast tissues

OBJECTIVE

The absorption spectrum obtained using diffuse reflectance measurements of malignant, fibroadenoma, and normal human breast tissues were studied. The spectral features in the spectrum were assigned to molecular components in the tissues.

BACKGROUND DATA

Over the past decade, the methods of fluorescence, excitation, and Raman spectroscopy have been studied as potential noninvasive diagnostic tools. Useful spectroscopic information may be obtained from absorption spectra of tissues as well. However, direct measurement of absorption spectra of tissues by conventional transmission means is complicated by multiple photon scattering in tissues. Diffuse reflectance spectrum offers an indirect way to obtain absorption spectrum.

METHODS

Excised malignant, fibroadenoma, and normal breast tissue samples without any treatment were obtained from pathology. Samples were placed in a quartz cuvette. The diffuse reflectance measurements between 250 nm to 650 nm were performed using an automated dual lamp spectrophotometer. The absorption spectra of breast tissues were obtained from the diffuse reflectance measurement.

RESULTS

Twenty-one invasive carcinoma, 20 mixed in situ and invasive carcinoma, 14 fibroadenoma, and 39 normal breast tissue samples were studied. The absorption spectra of breast tissues were obtained from diffuse reflectance spectra. Spectral features were assigned to DNA and proteins in human breast tissue. Amplitude of changes averaged over 275 nm to 285 nm and 255 nm to 265 nm and were found to be different for malignant, fibroadenoma, and normal breast tissues. These changes arise from differences in content of protein and DNA.

CONCLUSION

The peaks of absorption spectrum derived from diffuse reflectance measurements in the UV region revealed fingerprints from proteins and DNA components. The absorbance in the wavelength ranges of 275-285 nm and 255-265 nm were found to be different for malignant, fibroadenoma, and normal breast tissues. These differences provide a criterion to distinguish malignant from fibroadenoma and normal breast tissues.

Cisplatin and radiation sensitivity in human head and neck squamous carcinomas are independently modulated by glutathione and transcription factor NF-kappaB

BACKGROUND

Response to neoadjuvant cisplatin-based chemotherapy has been used to predict overall response to chemoradiation therapy and to select patients with head and neck squamous cell carcinoma (HNSCC) for organ preservation therapy in NCI and VA cooperative group trials. However, different molecular determinants have been reported to contribute to sensitivity of cells to cisplatin and radiation, including glutathione (GSH), and activation of nuclear factor-kappaB (NF-kappaB), a transcription factor that regulates cytoprotective genes. We have reported that NF-kappaB is constitutively activated in HNSCC, but the relationship of NF-kappaB to GSH and to cisplatin and radiation sensitivity in HNSCC is unknown.

METHODS

We examined human HNSCC lines to define the relationship of cisplatin and radiation sensitivity to intracellular GSH and NF-kappaB and determined whether HNSCC could be sensitized to these modalities by lowering the concentration of glutathione with L-buthionine sulfoximine or inhibiting activation of NF-kappaB by expression of a degradation-resistant mutant inhibitor-kappaBalpha.

RESULTS

Cisplatin resistance did not predict radiation resistance in three HNSCC cell lines, UM-SCC-9, 11B, and, 38. Resistance to cisplatin correlated with intracellular GSH, and depletion of GSH by treatment with L-BSO sensitized UM-SCC-9 cells to cisplatin but not radiation. Conversely, radiation resistance was correlated with activation of NF-kappaB. Expression of a mutant Inhibitor-kappaB after gene transfer inhibited NF-kappaB and sensitized UM-SCC-9 cells to radiation but not cisplatin.

CONCLUSIONS

GSH and transcription factor NF-alphaB can contribute independently to cisplatin and radiation sensitivity of human HNSCC. These results highlight the need to define molecular determinants of chemotherapy and radiation sensitivity for use in the selection of patients and as novel targets for therapy in future chemoradiation therapy trials for organ preservation in patients with HNSCC.

Prognostic value of c-erbB2 and other markers in patients treated with chemotherapy for recurrent head and neck cancer

BACKGROUND

Chemotherapy is widely used in patients with recurrent head and neck cancer, but no clear markers are available that can predict response to treatment or survival in these patients.

METHODS

Twenty-nine patients evaluated in this study had recurrent head and neck squamous carcinomas, previously treated with surgery and/or radiotherapy. Patients received either cisplatin and 5-fluorouracil (5-FU) (n = 15) or cisplatin and paclitaxel (Taxol) (n = 14). Expression of c-erbB2, p53, glutathione S-transferase pi, multidrug resistance-associated protein, thymidylate synthase, and glutathione synthetase were evaluated in biopsy tissues.

RESULTS

Response to chemotherapy was significantly correlated with improved survival (progression-free survival, p =.0005; overall survival, p =. 007). Of the factors examined, expression of c-erbB2 was associated with significantly decreased progression-free survival (p =.023) and overall survival (p =.029). This was seen in patients treated with cisplatin/taxol but not in patients treated with cisplatin/5-FU.

CONCLUSION

Expression of c-erbB2 may be a clinically useful predictor of survival in this group of patients.

Innate cellular fluorescence reflects alterations in cellular proliferation

BACKGROUND AND OBJECTIVE

The objective of this study was to examine the question of whether unique spectral patterns were associated with cell proliferation and could be identified by comparing the fluorescence pattern of slow to rapid growing cells.

STUDY DESIGN/MATERIALS AND METHODS

Three in vitro model systems, (A431 cells inhibited by EGF, serum-starved 3T3 fibroblasts, and normal oral epithelial cells exposed to TGF beta), were analyzed using fluorescence spectroscopy. Growth status was monitored by cell number, 3H-thymidine incorporation, and flow cytometry.

RESULTS

The excitation spectra (lambda ex 240-430 nm, lambda em 450 nm) effectively distinguished slow and rapid growing cells in all three systems. Statistical analysis of the ratios of the main broad peak (320-350 nm) to a point on the down-slope of the curve at 370 nm was statistically significant. Ratios in the emission scan (lambda ex 340 nm, lambda em 360-660 nm) could separate slow and rapid growing A431 and oral epithelial cells (P = 0.0001 and P = 0.023, respectively), but not slow and fast growing 3T3 cells (P = 0.56).

CONCLUSION

Innate cellular fluorescence has the potential to discriminate proliferating and nonproliferating cell populations.

Influence of melatonin on proliferation and antioxidant system in Ehrlich ascites carcinoma cells

The effects of oral supplementation of melatonin on growth of Ehrlich ascites carcinoma (EAC) cells implanted intraperitoneally in female mice were studied. Melatonin at 50 mg/kg body wt. reduced the viability and volume of Ehrlich ascites carcinoma cells and increased the survival of the treated mice. No significant change in intracellular reduced glutathione (GSH) content in EAC cells was observed indicating that GSH was not involved in the inhibitory effect of melatonin. The activity of glutathione-S-transferase in EAC cells was significantly increased. Flow cytometirc studies showed that melatonin not only delayed the progression of cells from G(0)/G(1) phase to S-phase of the cell cycle but also reduced DNA synthesis during cell cycle. In addition, the aneuploidy status was depressed in melatonin treated mice. Based on these data and the reduced viability in both in vitro and in vivo, it is suggested that melatonin might induce apoptosis in EAC cells.

Characterization of human soft-tissue sarcoma xenografts for use in secondary drug screening

We have established ten transplantable human soft-tissue sarcoma (STS) xenografts grown as subcutaneous tumours in the nude mouse. Nine xenografts originated from patients that needed chemotherapy in the course of their disease. The xenografts were tested for their sensitivity to maximum tolerated doses of five anti-cancer agents. Growth of treated tumours was expressed as a percentage of control tumour growth and a growth inhibition > 75% was measured for doxorubicin in 20% of the STS xenografts, for cyclophosphamide in 30%, for ifosfamide in 20%, for vincristine in 20%, whereas etoposide was not effective in the STS xenografts. In three out of ten STS xenografts MDR1 mRNA was detectable, but this was not related to the resistance against doxorubicin, vincristine or etoposide. Topoisomerase IIalpha mRNA expression levels did not reflect sensitivity to doxorubicin or etoposide. In all STS tissues, however, these levels were lower than topoisomerase IIalpha mRNA in a drug-sensitive human ovarian cancer xenograft. Glutathione concentrations and the activities of glutathione S-transferase, glutathione peroxidase and glutathione reductase were not related to resistance against the alkylating agents or doxorubicin. Of interest, in all STS tissues, glutathione S-transferase pi was the predominant isoenzyme present. In conclusion, chemosensitivity of the STS xenografts reflects clinical response rates in phase II trials on the same compounds in adult STS patients. Relatively low levels of topoisomerase IIalpha mRNA may partly account for intrinsic resistance against, for example, doxorubicin. Additional factors must contribute to moderate responsiveness to alkylating agents.

Role of glutathione, glutathione S-transferases and multidrug resistance-related proteins in cisplatin sensitivity of head and neck cancer cell lines

Resistance to chemotherapy is a major problem in the treatment of patients with head and neck squamous cell carcinoma (HNSCC). Important factors involved are drug detoxification by glutathione (GSH) and reduced drug accumulation due to active transport out of the cell by so-called 'multidrug resistance-related proteins'. We have studied a panel of eight HNSCC cell lines showing differences in sensitivity to the anti-cancer drug cisplatin. Our previous studies indicated that the IC50 values were inversely correlated with the intracellular accumulation of platinum (Pt). In the present study, cellular GSH levels were found not to be related to the IC50 values. The expression levels of the enzymes glutathione S-transferase (GST) alpha, mu, and pi, the multidrug resistance-related proteins P-glycoprotein (P-gp), multidrug resistance-associated protein (MRP) and the lung resistance protein (LRP) were determined semiquantitatively by means of immunocytochemistry. The levels of the GSTs, P-gp and LRP were not found to be correlated with the IC50 values of the HNSCC cell lines. Surprisingly, however, an inverse correlation was found between MRP levels and IC50 values. The MRP expression levels were in agreement with the results of the MRP functional assay, based on the transport of calcein across the cell membrane as performed for two of the cell lines. Further studies should prove whether other pump mechanisms or DNA repair are involved in the cisplatin accumulation and the subsequent HNSCC cell growth inhibition.

S-allylmercaptocysteine, a stable thioallyl compound, induces apoptosis in erythroleukemia cell lines

The antiproliferative potential of S-allylmercaptocysteine (SAMC), a stable organosulfur compound of aged garlic extract, has been investigated using two erythroleukemia cell lines, HEL and OCIM-1. It induces a dose-dependent inhibition of cell growth with a 50% lethal dose of 0.046 mM for OCIM-1 cells and 0.093 mM for HEL cells. [3H]thymidine incorporation was reduced in cells treated with this thioallyl compound, and analysis of high-molecular-weight DNA showed fragmentation compatible with apoptosis. Flow cytometric analyses of DNA revealed an abnormal cell cycle progression in both types of erythroleukemia cells, with the major portion of the unsynchronized cells in the G2/M phase. Measurement of acid-soluble free sulfhydryl groups showed an initial increase in response to SAMC followed by a progressive dose-dependent decrease with extended incubation of cells. We conclude from these studies that SAMC is an effective antiproliferative agent against erythroleukemia cells that induces cell death by apoptosis.

Relationship between the parameters cellular differentiation, doubling time and platinum accumulation and cisplatin sensitivity in a panel of head and neck cancer cell lines

Patients with head and neck squamous cell carcinoma (HNSCC) treated with cisplatin show a large inter-individual variation in tumor response. Little is known about factors that contribute to this variation. The aim of our study was to correlate the sensitivity to cisplatin with a number of cellular parameters using a panel of 10 human HNSCC cell lines. A 7-fold variation in response after 72 hr of exposure to cisplatin as determined in a colorimetric proliferation assay was observed. The IC50 values did not correlate with the DNA index, the cellular doubling time or the expression of differentiation markers. Intracellular platinum (Pt) concentrations were measured by atomic absorption spectroscopy after exposing the cells to 10 microM cisplatin for 1-72 hr. The intracellular Pt levels increased up to 24 hr. One cell line, derived from the tumor of a patient previously treated with radiotherapy, accumulated much more Pt than the other cell lines. For these other cell lines, a significant positive correlation was found between Pt accumulation and sensitivity. In conclusion, cisplatin-induced growth inhibition in HNSCC in vitro is generally positively correlated with cellular Pt levels. However, the fact that occasionally cancer cells can survive despite high intracellular Pt levels indicates that additional parameters are needed to explain a response unequivocally.

S-allylmercaptocysteine inhibits cell proliferation and reduces the viability of erythroleukemia, breast, and prostate cancer cell lines

Organosulfur compounds are the biologically active components of allium vegetables. Many health benefits have been ascribed to them, including inhibition of carcinogenesis. Inasmuch as several of these thioallyl compounds are quite unstable and others are rapidly inactivated in the body, we have investigated one of the stable components present in aged garlic extract, S-allylmercaptocysteine (SAMC), in an effort to determine whether it can inhibit proliferation of cancer cells. Proliferation and viability of two erythroleukemia cell lines, HEL and OCIM-1, two hormone-responsive breast and prostate cancer cell lines, MCF-7 and CRL-1740, respectively, and normal human umbilical vein endothelial cells in response to different concentrations of SAMC were studied for up to two weeks. There were variations in sensitivity to this organosulfur compound in the different cell lines examined, but the two hormone-responsive cancer cell lines of breast and prostate clearly were far more susceptible to the growth-inhibitory influence of the thioallyl compound. The antiproliferative effect of SAMC was limited to actively growing cells. Human umbilical vein endothelial cells that had reached confluence escaped the reduction in viability so noticeable in the cancer cell lines tested. Our studies thus give evidence of a direct effect of SAMC on established cancer cells.

Cell, tissue and organ culture as in vitro models to study the biology of squamous cell carcinomas of the head and neck

In vitro models are currently being used to study head and neck squamous cell carcinoma (HNSCC). Several hundred HNSCC cell lines have been established by various investigators and used to study a broad spectrum of questions related to head and neck cancer. The head and neck model with respect to multistage carcinogenesis is now complete. Several techniques exist for the culture of normal epithelial cells from the upper aerodigestive tract (UADT). The biology of these UADT cells (oral cavity, oropharynx, hypopharynx and larynx) is being studied. Successful culture of premalignant lesions (dysplastic mucosa, leukoplakia, erythroplakia) has resulted in establishment of a limited number of premalignant cell lines and cell cultures. HPV infection of normal oral epithelial cells for immortalization (approximately premalignant cells) coupled with transformation with carcinogens (malignant cells) has established an experimental model for progression. Two in vivo models for oral carcinogenesis, the 7,12 dimethylbenz(a)anthracene-induced hamster cheek pouch model and the 4-nitroquinoline-N-oxide rat oral model, have been established in culture. Thus, multistage carcinogenesis models have been established from both human tissues and animal models and include cultures of normal, premalignant and malignant cells. Culture techniques for growing dissociated primary tumor cells for short term experimental analysis are being used. The culture of normal or tumor tissue as organ/explant cultures allows for the maintenance of normal cell-cell and cell-matrix interaction, but limits experimentation since these cultures cannot be propagated. Several three dimensional model systems are being used to obtain this histological complexity but allow for experimentation. The ability to culture normal, premalignant and malignant cells coupled with the use of a variety of culture techniques, should allow for the continued growth and experimentation in head and neck cancer research.