Revisiting the use of the EORTC QLQ-STO22 to assess health-related quality of life of patients with gastric cancer: incorporating updated treatment options and cross-cultural perspectives.

BACKGROUND: The EORTC QLQ-STO22 (QLQ-STO22) is a firmly established and validated measure of health-related quality of life (HRQoL) for people with gastric cancer (GC), developed over two decades ago. Since then there have been dramatic changes in treatment options for GC. Also, East Asian patients were not involved in the development of QLQ-STO22, where GC is most prevalent and the QLQ-STO22 is widely used. A review with appropriate updating of the measure was planned. This study aims to capture HRQoL issues associated with new treatments and the perspectives of patients and health care professionals (HCPs) from different cultural backgrounds, including East Asia. METHODS: A systematic literature review and open-ended interviews were preformed to identify potential new HRQoL issues relating to GC. This was followed by structured interviews where HCPs and patients reviewed the QLQ-STO22 alongside new issues regarding relevance, importance, and acceptability. RESULTS: The review of 267 publications and interviews with 104 patients and 18 HCPs (48 and 9 from East Asia, respectively) generated a list of 58 new issues. Three of these relating to eating small amounts, flatulence, and neuropathy were recommended for inclusion in an updated version of the QLQ-STO22 and covered by five additional questions. CONCLUSIONS: This study supports the content validity of the QLQ-STO22, suggesting its continued relevance to patients with GC, including those from East Asia. The updated version with additional questions and linguistic changes will enhance its specificity, but further testing is required.

Breast cancer survivors: return to work and wage loss in selected hospitals in Malaysia.

PURPOSE: This study aimed, firstly, to assess the determinants of return to work (RTW), secondly, to explore the amount of annual wage loss, and finally, to discover the determinants of wage loss among breast cancer (BC) survivors. METHODS: A cross-sectional study design was used in this research. The data was collected via interview using a validated questionnaire. Logistic regression models were developed to discover the significant determinants of RTW and of wage loss among BC survivors. RESULTS: A total of 256 BC survivors were included in this study. The analysis showed that there was a 21% loss of or reduction in mean income within 1 year after diagnosis. The significant predictors of RTW are being a government employee, having reduced wages or wage loss, and if the case had been diagnosed 1 year or more ago. Being a private sector employee and having a late stage of cancer was a barrier to RTW. The main risk factors for reduced wages or wage loss were belonging to the age group of 40-59 years, being of Chinese or Indian ethnicity, having low educational status, and not returning to work. However, belonging to the higher monthly income group (earning > RM 2000) is a protective factor against the risk of reduced wages or wage loss. CONCLUSIONS: Non-RTW and wage loss after diagnosis of BC may result in the survivors experiencing a significant financial burden. Assessment of these patients is becoming more crucial because more women participate in the workforce in Malaysia nowadays and because BC is managed using multiple treatment modalities with their consequences could lead to long absences from work.

Influence of testosterone on mean arterial pressure: A physiological study in male and female normotensive WKY and hypertensive SHR rats.

Introduction Testosterone plays an important role in the blood pressure regulation. However, information with regard to the effect of this hormone on blood pressure in normotensive and hypertensive conditions is limited. Therefore, in this study, the relationship between plasma testosterone level and mean arterial pressure (MAP) was investigated under these conditions. Methods Normotensive Wistar-Kyoto (WKY) and hypertensive Spontaneous Hypertensive (SHR) male and female rats were gonadectomized with female rats treated with testosterone. Estrous cycle stages of intact female rats of both strains were identified by vaginal smear. Pressure in the carotid artery of anesthetized rats was measured via direct cannulation technique. The blood was withdrawn for plasma testosterone level measurement by enzyme-linked immunosorbent assay. Results Treatment of ovariectomized female WKY and SHR rats with testosterone for 6-week duration has resulted in MAP to increase (P < 0.05). In male WKY and SHR rats, MAP and plasma testosterone levels decreased by orchidectomy (P < 0.05). No significant differences in MAP and plasma testosterone levels were observed in intact female WKY and SHR rats between stages of the estrous cycle. Conclusions The effects seen in testosterone-treated ovariectomized female rats and in orchidectomized male rats suggested that testosterone could play an important role in causing the blood pressure to increase.

Epigenetic Control of the Vasopressin Promoter Explains Physiological Ability to Regulate Vasopressin Transcription in Dehydration and Salt Loading States in the Rat.

The synthesis of arginine vasopressin (AVP) in the supraoptic nucleus (SON) and paraventricular nucleus (PVN) of the hypothalamus is sensitive to increased plasma osmolality and a decreased blood volume, and thus is robustly increased by both dehydration (increased plasma osmolality and decreased blood volume) and salt loading (increased plasma osmolality). Both stimuli result in functional remodelling of the SON and PVN, a process referred to as functional-related plasticity. Such plastic changes in the brain have recently been associated with altered patterns of DNA methylation at CpG (cytosine-phosphate-guanine) residues, a process considered to be important for the regulation of gene transcription. In this regard, the proximal Avp promoter contains a number of CpG sites and is recognised as one of four CpG islands for the Avp gene, suggesting that methylation may be regulating Avp transcription. In the present study, we show that, in an immortalised hypothalamic cell line 4B, the proximal Avp promoter is highly methylated, and treatment of these cells with the DNA methyltransferase inhibitor 5-Aza-2'-deoxycytidine to demethylate DNA dramatically increases basal and stimulated Avp biosynthesis. We report no changes in the expression of DNA methyltransferases, Dnmt1 and Dnmt3a, whereas there is decreased expression of the demethylating enzyme ten-eleven-translocation 2, Tet2, in the SON by dehydration and salt loading. We found higher methylation of the SON Avp promoter in dehydrated but not salt-loaded rats. By analysis of individual CpG sites, we observed hypomethylation, hypermethylation and no change in methylation of specific CpGs in the SON Avp promoter of the dehydrated rat. Using reporter gene assays, we show that mutation of individual CpGs can result in altered Avp promoter activity. We propose that methylation of the SON Avp promoter is necessary to co-ordinate the duel inputs of increased plasma osmolality and decreased blood volume on Avp transcription in the chronically dehydrated rat.

Ventricular tachycardia storm: a case series and literature review.

INTRODUCTION: Ventricular tachycardia (VT) storm is an uncommon but life-threatening condition. We describe the incidence, causes and management of VT storm among patients admitted to the coronary care unit of a large tertiary hospital. MATERIALS AND METHODS: Between 1 November 2009 and 30 April 2010, 198 patients were admitted to the coronary care unit and 7 (3.5%) presented with VT storm. A retrospective review of their records was conducted. The mean follow-up period was 268 (196 to 345) days. RESULTS: The mean age was 67 years and 4 patients were male. One patient had a previous myocardial infarction. All had abnormal left ventricular ejection fraction, median of 30%. Acute myocardial infarction (4 patients) was the most common trigger, followed by decompensated heart failure (1), systemic inflammatory response syndrome on a background of non-ischemic dilated cardiomyopathy (1) and bradycardia-induced polymorphic VT (1). Three patients had polymorphic VT and the rest had monomorphic VT. Intravenous amiodarone, lignocaine, overdrive pacing and intra-aortic balloon pump counterpulsation were useful in arrhythmia control. Three patients underwent coronary revascularization, 3 patients received implantable cardioverter-defibrillators, 1 had a permanent cardiac pacemaker, 1 died during the acute episode. Five out of the 6 survivors were prescribed oral beta-blockers upon discharge. On follow-up, none of the patients had a recurrence of the tachyarrhythmia. CONCLUSION: Acute myocardial infarction was the main trigger of VT storm in our patients. Intravenous amiodarone, lignocaine, overdrive pacing and intra-aortic balloon pump counterpulsation were useful at suppressing VT storm.

Earnings among people with spinal cord injury.

STUDY DESIGN: Secondary analysis of cross-sectional data. OBJECTIVES: To identify differences in earnings among participants with spinal cord injury (SCI) and their relation to demographic, injury, educational and employment-related factors. SETTING: People living with SCI in the community who were members of a disability support organization. METHODS: A total of 76 members who have had traumatic SCI for at least 2 years, between 15 and 64 years of age at time of study and were working before SCI were interviewed over the phone. The earnings were categorized as more, same or less than before SCI or no income for those unemployed. RESULTS: Of the 76 participants (who averaged about 15.1 years post SCI), only 13 participants (17.1%) were earning more than before injury, whereas majority were in the category of having no income, being unemployed at time of study, n=36 (47.4%). Factors positively related to earnings were having more years in education, both at time of injury and at time of survey. As anticipated, those currently in full time and paid employments were earning more while receipt of financial compensation was negatively related to earnings. CONCLUSION: Despite a lengthy period of time post SCI, only a minority were earning more, reflecting poorly on the quality of post SCI employment experience. The rehabilitation team should therefore focus on improving both educational and vocational opportunities for persons with SCI and aim for full time, paid employments. The current workers' compensation scheme renders the recipient at a static income and may need to be revised.

Self management pilot study on women with breast cancer: lessons learnt in Malaysia.

OBJECTIVE: With increasing survival rates, breast cancer is now considered a chronic condition necessitating innovative care to meet the long-term needs of survivors. This paper presents the findings of a pilot study on self-management for women diagnosed with breast cancer and their implications for Asian health care providers. METHODS: A pre-test/ post-test pilot study was conducted to gain preliminary insights into program feasibility and barriers to participation, and to provide justification for a larger trial. RESULTS: The study found the 4 week self-management program feasible and acceptable, with a favourable trend in quality of life. The recruitment barriers ranged from competing medical appointments, uncollaborative health providers, linguistic barriers and social-household concerns. Supporting facilitators identified were family, health professionals and fellow participants ("buddies"). Lessons from the study are discussed with regard to Asian health providers. CONCLUSION: There is preliminary evidence that self management is a workable and potentially useful model even in an Asians entrenched-hierarchical medical model of care. The initial challenge was breaking down barriers in acceptancee of a collaborative stance. A clinical trial is now warranted to gather more evidence.

Perceived barriers to self-management in Malaysian women with breast cancer.

Naturalistic inquiry using focus group interviews was undertaken to explore experiences and perceived barriers to self management in women with breast cancer. The aim was to identify their perceived barriers to self management to aid the development of rehabilitation programmes. Successful programmes are strongly linked to patients' perceived needs. Four focus groups consisted of 39 women, were purposively recruited. Women's needs within the three areas of medical, emotional and role management of breast cancer were explored. The main barriers were unavailability of information, inability to access services-and-support, and socioeconomic-cultural issues (entrenched myths, low-socioeconomic status, and inadequate insurance-health legislative coverage). The findings provide the critically lacking 'expert-view' of survivors, who verified the importance of the medical, emotional and role management tasks, and highlighted barriers and structural solutions. With breast cancer becoming recognised as a form of chronic illness, this study is timely.

Tarsometatarsal joint injuries--review of clinical presentation and surgical treatment.

The tarsometatarsal (Lisfranc) joint suffers a spectrum of injuries ranging from solely ligamentous injury to fracture dislocation. The authors evaluated eighteen consecutive patients who underwent surgery for tarsometatarsal joint injuries, utilising 4.5 mm cancellous screws and 1.6 mm K-wires. The outcome of function and anatomical reduction were assessed by AOFAS (American Orthopedic Foot and Ankle Society) midfoot score and radiography. Patients with only ligamentous injury scored poorer partly due to delay in diagnosis and the nature of the injury. The technique used maintained anatomical reduction at the time of review.

Reliability and validity of the Pressure Management Inventory in a Malaysian population.

There is a general lack of valid tools to measure work stress of Malaysian. This study examines the validity and reliability of the Pressure Management Inventory (PMI). Reliability was evaluated using test retest method, and its correlation coefficient was calculated using Pearson's r. Internal consistencies were examined using Cronbach's Alpha. For precision, the Intraclass coefficients (ICC) were calculated for all the scales. Face Validity and Content Validity were assessed using an open-ended questionnaire on 6 content experts (psychiatrists in HKL). The results show good internal consistencies (alpha < or = 0.7) for most subscales, with the best results in the 'Pressure Scale'. The weak scales are 'Individual-Differences' scale and 'Social Support' scale. The test-retest correlation coefficients were significant at the level of p<0.001 for all, except one scale. The ICC coefficients were high (>0.7) for most scales, particularly for Pressure, Health and Coping Scales. The PMI is a suitable, reliable and valid tool to measure stress of Malaysians. More in-depth study with a wider sampling needs to be carried out to add confidence of its usage on Malaysians.

Profile of women presenting for abortions in Singapore at the National University Hospital.

The study was conducted to profile women seeking abortions at the National University Hospital, with particular interest in the trend of teenage pregnancies with the aim of identifying risk factors for late presentation for abortions. All patients who underwent an abortion at our center from January 1, 1996 to December 31, 2000 were recruited. Data were entered into a prepared questionnaire during the mandatory pre-abortion counseling sessions and completed at the 6-week post-abortion follow-up. This was then keyed into a database (SPSS Version 10), and the results were analyzed. Multivariate analysis was used in identifying risk factors associated with late presentation for abortions. Chi-square analysis of variables was used where relevant. A total of 1370 women presented for induced abortions during the period of study. The mean age of women was 29.6 years. Most women were either homemakers (35.3%) or semi-skilled workers (28.5%) with at least a secondary school education (58.3%). The majority were married (75.5%). There was a significant trend in the proportion of single women seeking abortions, from 18.3% in 1996 to 27.8% in 2000 (p < 0.05). At the same time, the proportion of women presenting for repeat abortions also increased from 13.8% in 1996 to 33.2% in 2000 (p < 0.05). Teenage abortions made up 117 (8.5%) of the study group, of which 95% were single women. Significant proportions (52.1%) were students at the time of abortion. In contrast to women above 20 years of age, pregnant teenagers were more likely not to have used any contraception (67.1% vs. 37.3%) and more likely to present late for abortion (18.8% vs. 10.4%). Teenage pregnancies are a major risk factor for late presentation for abortions. This emphasizes the need for availability and easy access to early abortion counseling, and the need for sex education with use of contraception starting in schools, to reduce abortions among teenagers.

A demographic profile of patients undergoing transurethral resection of the prostate for benign prostate hyperplasia and presenting in acute urinary retention.

OBJECTIVE: To evaluate, in a prospective study, the demographic profile of patients with benign prostate enlargement who presented in acute urinary retention (AUR). PATIENTS AND METHODS: The study comprised all patients admitted for transurethral resection of the prostate and categorised into two groups, i.e. those presenting in AUR or electively. The factors evaluated included the length of hospitalization, the patients' occupation, their duration of symptoms and reasons for not seeking treatment. RESULTS: There was no significant difference in the mean age and occupational status of the two groups but those in AUR had more complications and a longer hospital stay after surgery; 60% of these men had had their urinary symptoms for > 1 year. When asked why they did not seek treatment earlier, 35% reported fear of surgery, while 41% thought that their symptoms were a normal part of ageing. CONCLUSION: There is a need to raise the level of public awareness of benign prostatic enlargement because those who present with AUR incur excess morbidity and longer hospitalization that could otherwise be avoided through earlier treatment and elective surgery.

Unknown identification using reference mass spectra. Quality evaluation of databases.

The high success of the "uncertified" mass spectrometry spectral collection started in 1956 demonstrated qualitatively that a partial reference mass spectrum, even one measured routinely, can be of real value. Correct matchings were still possible despite reference errors, which almost never led to close matches that were incorrect. This study shows quantitatively that the number of different compounds, not the number of peaks in a spectrum, is by far the most important determinant of database efficiency for identifying a "global" unknown. A statistical evaluation of matching performance shows that only 6, 12, and 18 peaks in a reference spectrum are 13%, 67%, and 96%, respectively, as valuable as hundreds of peaks. Also, a separately measured second spectrum of the same compound is 50% as valuable as the first. Database expansion that tripled the number of possible wrong answers only reduced the proportion of correct identifications by 5%. Corrections of a mass or abundance error in each of six reference spectra increase the database matching performance by as much as the addition of one spectrum of a new compound. A new "matching quality index" based statistically on these values indicates that the largest database is also by far the most effective for matching unknowns.

Comparison of algorithms and databases for matching unknown mass spectra.

The most used algorithms for the identification of electron-ionization mass spectra are INCOS and probability based matching (PBM). For unknown spectra of high purity, approximately 75% of rank 1 answers are correct for both algorithms, matched against the National Institute of Standards and Technology 62,235 spectrum database. With matching criteria that retrieve 50% of the possible correct answers from the Wiley 228,998 spectrum database, 54% of the PBM and 42% of the INCOS answers are correct; for 85% purity unknowns, 48% and 27% are correct. For an unknown spectrum of two compounds, neither was reported in the first three INCOS answers; eight of the first ten PBM answers identify both components.

Effect of buthionine sulfoximine on PtII and PtIV drug accumulation and the formation of glutathione conjugates in human ovarian-carcinoma cell lines.

Glutathione (GSH) has often been implicated in the mechanism of resistance to platinum anti-cancer drugs. It has been suggested that GSH may reduce the cytotoxicity of these drugs by forming inactive conjugates and by enhancing the repair of DNA-platinum crosslinks. In the present study we have examined the effect of D,L-buthionine-S,R-sulfoximine (BSO) pretreatment on the accumulation of platinum in a sensitive (CHI) and 2 relatively resistant (SKOV-3, HX/62) human ovarian-carcinoma cell lines following exposure to PtII- (cisplatin, carboplatin) and PtIV-drugs (tetraplatin). The metabolism of cisplatin and tetraplatin (particularly the extent of platinum-GSH conjugate formation) in the presence and absence of BSO pre-treatment was also examined in these cell lines. BSO pre-treatment reduced the accumulation of PtII but not that of PtIV drugs in the relatively resistant SKOV-3 and HX/62 cell lines. It had no effect on the accumulation of either class of drugs in the sensitive CHI cells. Metabolism studies with cisplatin showed that the SKOV-3 and HX/62 cells, which contained 2- to 3-fold higher levels of GSH, were able to inactivate a greater proportion of cellular cisplatin, by the formation of platinum-GSH conjugates, than the CHI cells. A significant inhibition in formation of these conjugates, by BSO-induced depletion of cellular GSH (over 80%), did not, however, increase cisplatin concentration in the resistant cells. In contrast, a small increase in cisplatin concentration was observed in the sensitive cells following BSO pre-treatment. Comparison of cisplatin and tetraplatin metabolism in the SKOV-3 cells indicated that a greater proportion of the latter drug was inactivated by formation of GSH conjugates. BSO-induced depletion of cellular GSH in this cell line significantly reduced the formation of such conjugates from both drugs. However, concomitant increases in intracellular levels of reactive species were observed only after tetraplatin exposure. Our data suggest that the greater potentiation of PtIV- compared with PtII-drug cytotoxicity in the relatively resistant cell lines following 24 hr BSO pre-treatment may be caused by a differential effect of BSO on the metabolism and cellular distribution of these drugs. A BSO-induced reduction in PtII- but not PtIV-drug accumulation in these cells may also partially contribute to the differential potentiation of cytotoxicity of these drugs.

Reduced drug accumulation as a major mechanism of acquired resistance to cisplatin in a human ovarian carcinoma cell line: circumvention studies using novel platinum (II) and (IV) ammine/amine complexes.

Acquired resistance to cisplatin (cis-diamminedichloroplatinum (II)) has been generated in vitro in the 41M human ovarian carcinoma cell line, established from a previously untreated patient. Three cisplatin-resistant variants were selected at approximately 2, 4 and 6-fold resistance (in terms of 50% inhibitory concentrations), in order to study the underlying mechanisms of acquired cisplatin resistance. Compared to the parent line, platinum accumulation following exposure to equimolar concentrations of cisplatin was on average (across the entire concentration range) 2.9, 3.6 and 4.8-fold lower in the 41McisR2, 41McisR4 and 41McisR6 cell lines, respectively. Thus the difference in uptake corresponded closely with their resistance factor in the three resistant variants. Moreover, a significant reduction in platinum accumulation was observed as early as 5 min after exposure to cisplatin in the 41M vs 41McisR6 cell lines. Platinum accumulation was similar in all cell lines following exposure to equitoxic concentrations (2 h IC50) of cisplatin. Enhanced efflux of drug was not observed between the 41M and 41McisR6 cells. In addition, there was no difference in intracellular glutathione (GSH) levels. Our previous studies have shown no indication of metallothionein involvement and the decrease in cisplatin uptake in the 41McisR6 cells was reflected by a similar reduction in DNA interstrand cross-links (ISC) formation. These results suggest that the mechanism of acquired resistance to cisplatin in the 41McisR6 cell line may be predominantly due to reduced drug uptake. The 41McisR6 cells were not found to be cross-resistant to ouabain, a postulated specific inhibitor of sodium-potassium adenosine triphosphatase (Na+, K(+)-ATPase), suggesting that decreased cisplatin accumulation in these cells is probably not regulated by alterations in their Na+, K(+)-ATPase levels, and Na+ potential across the plasma membrane. Cellular accumulation of a novel class of platinum (IV) ammine/cyclohexylamine dicarboxylates, which exhibit enhanced cytotoxicity over cisplatin and completely circumvent resistance to cisplatin in the 41McisR line, was also examined. The data suggests that increased accumulation of these compounds, as a result of their enhanced lipophilicity, could account for the dramatic increase in their potency over cisplatin.

Comparison of cellular accumulation and cytotoxicity of cisplatin with that of tetraplatin and amminedibutyratodichloro(cyclohexylamine)platinum(IV) (JM221) in human ovarian carcinoma cell lines.

We have compared the cellular accumulation and cytotoxicity of three platinum compounds in a panel of five human ovarian carcinoma cell lines. The cell lines, which were established from both untreated and pretreated patients, showed a wide range in sensitivity to cisplatin and other platinum drugs. The panel consisted of two sensitive (41M, CH1), one in vivo acquired resistant (PXN/94) with moderate sensitivity, and two intrinsically resistant (SKOV-3, HX/62) cell lines. The cisplatin 2-h concentration of drug required to inhibit cell growth by 50% compared with vehicle treated control cells (IC50 values) for these cell lines were in the following order: CH1 < 41M < PXN/94 < SKOV-3 < HX/62. None of the cell lines showed saturation of platinum accumulation (per mg protein) at 2 h after exposure to cisplatin concentrations of up to 500 microM. The highest cellular platinum accumulation was observed in the sensitive 41M cell line which was established from an untreated patient. The lowest accumulation was found in the intrinsically resistant HX/62 cell line. The rate of platinum accumulation at an equimolar concentration of cisplatin was 41M > SKOV-3 > CH1 > PXN/94 > HX/62. The relationship between drug accumulation and cytotoxicity was evaluated by comparing 2-h IC50 values with platinum accumulation following exposure to both equimolar and equitoxic doses of the agent. The results suggest that reduced drug accumulation may play a partial role in the mechanism of intrinsic resistance to cisplatin in one cell line (SKOV-3) and a major role in another (HX/62), where reduced accumulation is attributable to reduced uptake rather than enhanced efflux. Decreased drug accumulation may also contribute significantly to the lower sensitivity of the PXN/94 cell line to cisplatin. Interestingly, both the PXN/94 and the sensitive CH1 cell lines, which were established from patients pretreated with platinum drugs, showed reduced drug accumulation relative to the 41M cell line. Cellular accumulation of tetraplatin and JM221 [(ammine)dibutyratodichloro(cyclohexylamine)platinum(IV)], a novel platinum(IV) dicarboxylate complex exhibiting enhanced cytotoxicity compared to cisplatin, was also examined. Comparison with platinum accumulation from cisplatin suggests that the increased cytotoxicity of tetraplatin and JM221 may be related to their increased accumulation. Significantly both agents are more lipophilic than cisplatin, which may account partially for their improved uptake in cisplatin resistant cells.

Mechanism-related circumvention of acquired cis-diamminedichloroplatinum(II) resistance using two pairs of human ovarian carcinoma cell lines by ammine/amine platinum(IV) dicarboxylates.

Acquired resistance to cisplatin has been generated in vitro in two human ovarian carcinoma cell lines: 41M, established from a previously untreated patient; and CH1, from a patient previously treated with cisplatin and cis-diammine-1,1-cyclobutane dicarboxylatoplatinum(II) (carboplatin). In neither cell line with acquired resistance did intracellular detoxification (via increased glutathione or metallothioneins) appear to be a major determinant of resistance. Resistance in 41McisR (resistance factor of 4.7) appeared to be due predominantly to a reduced platinum accumulation (levels were only 23.8% in 41McisR versus 41M). This was also reflected at the DNA level by a similar level of reduced DNA interstrand cross-links and total platinum-DNA adducts measured immediately after a 2-h exposure to cisplatin in 41McisR versus 41M. Conversely, for CH1cisR (resistance factor of 6.5), platinum accumulation, and initial numbers of DNA-interstrand cross-links and total DNA-platinum adducts were not significantly different from the parent CH1 line. This is suggestive of a resistance mechanism involving increased DNA repair or tolerance to platinum-DNA adducts operating in the CH1cisR/CH1 pair of lines. Cross-resistance to carboplatin and partial cross-resistance to the 1,2-diaminocyclohexane-containing agent, (trans-d,l)-1,2-diaminocyclohexane tetrachloroplatinum(IV) (tetraplatin), was observed in both pairs. However, two novel platinum(IV) ammine/amine dicarboxylates, ammine dibutyratodichloro(cyclohexylamine)platinum(IV) (JM221) and ammine dibenzoatodichloro(propylamine)platinum(IV) (JM244), completely circumvented resistance in 41McisR to produce some collateral sensitivity (resistance factors of 0.67 and 0.54, respectively) but showed cross-resistance in CH1cisR (resistance factors of 3.7 and 4.6). In contrast to the data for cisplatin, intracellular platinum levels were not significantly different between the 41M and 41McisR pair of cell lines after exposure to JM244. These results suggest that the ammine/amine platinum(IV) dicarboxylates, which show considerably greater in vitro cytotoxicity than cisplatin, are capable of circumventing acquired cisplatin resistance which is due to decreased intracellular accumulation but are not able to overcome resistance at the level of DNA platination and removal.

Establishment and characterization of an in vitro model of acquired resistance to cisplatin in a human testicular nonseminomatous germ cell line.

Clinically, human testicular nonseminomatous germ cell tumors exhibit remarkable sensitivity to platinum-based chemotherapy. To define better the mechanistic basis for this unusual sensitivity, the biochemical determinants of platinum-induced cytotoxicity have been investigated in a human testicular tumor cell line (GCT27) established from a previously untreated patient and in an in vitro derived 5.6-fold cisplatin-resistant stable variant (GCT27cisR). Compared to 12 ovarian and 5 cervical human tumor cell lines, the parent GCT27 line was among the most sensitive to the cytotoxic effects of both cisplatin (dosage producing 50% inhibition, 0.2 microM) and carboplatin (dosage producing 50% inhibition, 2.9 microM), thus reflecting clinical data. A 4-day exposure sulforhodamine B-staining assay was used to determine that GCT27cisR was cross-resistant to carboplatin and iproplatin and the classical bifunctional alkylating agents melphalan and chlorambucil. Partial cross-resistance was observed to tetraplatin, methotrexate, and mitomycin C. No cross-resistance was observed to Adriamycin, etoposide, vinblastine, bleomycin, 1-beta-D-arabinofuranosylcytosine, and 5-fluorouracil. Intracellular cisplatin accumulation across the dose range 2.5-100 microM (for 2 h) was 1.6 +/- 0.39-fold (mean +/- SD) greater for the parent line. There was no significant difference in glutathione levels between the two lines. The acquired resistance line was 1.9-fold more resistant than the parent line to the cytotoxic effects of cadmium chloride. There was no significant difference between the two lines, however, in the total amounts of platinum bound to DNA after cisplatin exposure (25, 50, or 100 microM for 2 h). The removal of total platinum adducts from DNA was significantly faster for GCT27cisR compared to the parent line (half-times of removal, 32 and 67 h, respectively). These data suggest that the abnormal sensitivity of the parent testicular tumor cell line to platinum-containing anticancer drugs may be due predominantly to an inherent defect in the ability of these cells to remove platinum from their DNA. This defect is apparently lost in the acquired resistance counterpart. Reduced intracellular accumulation and increased cytoplasmic concentrations of metallothionein may also contribute, in part, to the acquisition of cisplatin resistance in this model.