Pitfalls of positivity–new perspectives on the futility of negating negativity

The claim that “thinking positive” betters one's life has become pervasive in our contemporary culture. Proponents of this style of reasoning, including the head of the positive psychology movement, Martin Seligman, claim their goal is to create a field focused on human well-being and the conditions, strengths and virtues that allow people to thrive, and back their standpoint with a great number of studies.

However, critics of the movement have, first of all, pointed out flaws in some of the concepts and studies backing them, and second, performed experiments of their own which show not only that forced positive thinking doesn’t help, but can sometimes be harmful.

More worrisome than disputes in the therapeutic community is the tendency of mass media and our commodified society to abuse these approaches, the end result being a whole scope of popular psychology books which promise wealth, happiness and ideal partners to those prepared to “believe”, and the presence of a horde of self-appointed gurus promising easy answers and quick solutions. This is only a symptom of our contemporary postmodern condition, one well phrased by the Slovenian philosopher Žižek - “the commandment of the ruling ideology is ‘enjoy!”’.

From philosophers of negativity (Nietzsche, Schopenhauer) to psychotherapists dealing with automatic negative thoughts, we come to our proposed field of research in the “neuroscience of negativity”, a search for the biological underpinnings of positivity/negativity, focusing primarily on their relation to Cloningers’ dimensions of personality and mood disorders.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

OC-07 - Decoding risk for thromboembolic events in lymphoma patients

INTRODUCTION

There are few prediction tools for estimating the risk of thrombosis but they are based on studies performed on hospitalized medical patients without cancer or on hospitalized neutropenic cancer patients without special consideration to lymphoma patients.

AIM

Aim of our study was to determine incidence of thromboembolic (TE) events in patients with non Hodgkin lymphoma (NHL), Hodgkin lymphoma (HL) and chronic lymphocytic leukemia (CLL)/ small lymphocytic lymphoma (SLL) who were hospitalized to the lymphoma department in the Clinic of hematology, Clinical Center Serbia, Belgrade and Clinic of hematology, Clinical Center Kragujevac. Also, we assessed 2 predictive models (Padua and Khorana score) and create new model for the identification of lymphoma patients at risk for thromboembolism.

MATERIALS AND METHODS

We reviewed all medical records of patients with with NHL, HL and CLL/SLL diagnosed and treated at two previously mentioned institution between January 2006 and December 2014.

RESULTS

The study population included 1820 eligible lymphoma patients. Of all the patients included in the study, 99 (5.4%) developed at least one TE during a follow-up period of 3 months from the end of therapy. In the final multivariate analysis, the following variables were independently associated with risk of TE: previous VTE and/or arterial events, reduced mobility (ECOG 2-4), obesity (BMI >30 kg/m(2)), extranodal localization, mediastinum involvement, development of neutropenia during therapy and hemoglobin level less than 100g/L. Subsequently, we assigned points for the risk model based on the regression coefficients obtained from the final model and developed Thrombosis Lymphoma (ThroLy) score consisting of all significant variables from the multivariate analysis. The Throly score was arrived at by assigning 2 points for all parameters with an OR >5 in multivariate regression analyses (e.g., previous VTE and arterial events, mediastinum involvement, and BMI) and 1 point for rest all other significant variables. Finally, population were divided into 3 risk categories for TE based on the score from the risk model: low (score 0-1), intermediate (score 2-3) and high (score >3). High risk score had a positive predictive value (probability of TE in those designated high risk) of 65.2%.

CONCLUSIONS

Significance of our investigation is development of score that help phisicians to recruit lymphoma patients at risk for development of thromboembolic complications. Also, we can say that our score is dynamic allowing us to change approach during different phase of therapy and is not limited to outpatient settings or with some complicated laboratory analysis.

Kraepelin's ghost: Late onset schizophrenia, dementia (non)praecox, or paraphrenia? (case report)

Introduction

It is difficult to establish whether a patient has late onset schizophrenia or frontotemporal dementia. The object of the following case report is to point out the difficulty of making a differential diagnosis between these two entities.

Case summary

A 49-year-old female patient was admitted to our hospital after presenting with auditory and visual hallucinations, formal thought disorder, persecutory delusions, ideas of reference, insomnia. Memory, executive function and attentional tasks were severely compromised. Computerized tomography showed incipient frontal lobe atrophy. There were no significant abnormalities found in blood and urine samples or physical and neurological examinations. After showing no response to olanzapine, and extrapyramidal side effects to fluphenazine, risperidone was initiated which subsequently led to complete withdrawal of positive symptoms.

Discussion

Patients presenting with psychotic symptoms after the age of 40 presented a diagnostic quandary, as they were less likely to present with negative symptoms, formal thought disorder or affective blunting, and more likely to have systematised delusions and visual hallucinations. Frontotemporal dementia is a disorder that can present itself with cognitive decline and a large range of psychiatric symptoms. The risk of late onset schizophrenia is greater in women, possibly implicating a causative role of female sex hormones. Atypical antipsychotics risperidone and olanzapine seem to be an adequate treatment.

Conclusion

Schizophrenia is a heterogeneous disease with a large variety of clinical manifestations. Special care should be given to patients with age over 40, including neurocognitive assessment, laboratory and hormone tests, and a long-term follow-up.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

A randomized phase II study of ganetespib, a heat shock protein 90 inhibitor, in combination with docetaxel in second-line therapy of advanced non-small cell lung cancer (GALAXY-1)

BACKGROUND

This trial was designed to evaluate the activity and safety of ganetespib in combination with docetaxel in advanced non-small cell lung cancer (NSCLC) and to identify patient populations most likely to benefit from the combination.

PATIENTS AND METHODS

Patients with one prior systemic therapy for advanced disease were eligible. Docetaxel (75 mg/m(2) on day 1) was administered alone or with ganetespib (150 mg/m(2) on days 1 and 15) every 3 weeks. The primary end points were progression-free survival (PFS) in two subgroups of the adenocarcinoma population: patients with elevated lactate dehydrogenase (eLDH) and mutated KRAS (mKRAS).

RESULTS

Of 385 patients enrolled, 381 were treated. Early in the trial, increased hemoptysis and lack of efficacy were observed in nonadenocarcinoma patients (n = 71); therefore, only patients with adenocarcinoma histology were subsequently enrolled. Neutropenia was the most common grade ≥3 adverse event: 41% in the combination arm versus 42% in docetaxel alone. There was no improvement in PFS for the combination arm in the eLDH (N = 114, adjusted hazard ratio (HR) = 0.77, P = 0.1134) or mKRAS (N = 89, adjusted HR = 1.11, P = 0.3384) subgroups. In the intent-to-treat adenocarcinoma population, there was a trend in favor of the combination, with PFS (N = 253, adjusted HR = 0.82, P = 0.0784) and overall survival (OS) (adjusted HR = 0.84, P = 0.1139). Exploratory analyses showed significant benefit of the ganetespib combination in the prespecified subgroup of adenocarcinoma patients diagnosed with advanced disease >6 months before study entry (N = 177): PFS (adjusted HR = 0.74, P = 0.0417); OS (adjusted HR = 0.69, P = 0.0191).

CONCLUSION

Advanced lung adenocarcinoma patients treated with ganetespib in combination with docetaxel had an acceptable safety profile. While the study's primary end points were not met, significant prolongation of PFS and OS was observed in patients >6 months from diagnosis of advanced disease, a subgroup chosen as the target population for the phase III study.

Determinants of intention to work abroad of college and specialist nursing graduates in Serbia

BACKGROUND

In a country with a poor economy and limited job opportunities, the outmigration of students is not commonly perceived as a problem but rather is perceived as a solution to the high unemployment facing young health professionals.

OBJECTIVES

Study objectives were to identify the prevalence of intention to work abroad of nursing graduates to point to the predictors of intention to work abroad and predictors of having a firm plan to work in a foreign country.

DESIGN

Descriptive study, a survey.

SETTINGS

College and specialist nursing schools, Serbia.

PARTICIPANTS

719 nursing graduates from the 2012/2013 school year.

METHODS

Voluntarily completed a questionnaire that was designed with regard to similar surveys administered in EU-candidate countries during the pre-accession period. Data were analysed with descriptive and multivariate regression analyses.

RESULTS

Almost 70% (501) of respondents indicated an intention to work abroad. Of the nurses, 13% already had established a firm plan to work abroad. Single graduates and those with a friend or relative living abroad were more likely to consider working abroad than were their counterparts (odds ratios were 2.3 and 1.7, respectively). The likelihood of considering working abroad decreased by 29% when the individuals' financial situation was improved. Factors associated with having a firm plan were previous professional experience in a foreign country, having someone abroad and financial improvement (5.4 times, 4.8 times and 2 times greater likelihood, respectively).

CONCLUSIONS

The high prevalence of intention to work abroad suggests the need to place the issue of the out-migration of nursing graduates on the policy agenda. College and specialty nursing graduates and health technicians are prepared to work abroad in search of a better quality of life, better working conditions and higher salaries.

Enhanced International Prognostic Index (NCCN-IPI), Charlson Comorbidity Index and absolute lymphocyte count as predictors for survival of elderly patients with diffuse large B cell lymphoma treated by immunochemotherapy

Diffuse large B cell lymphoma (DLBCL) affects more commonly patients over 60 years. These patients have vast number of comorbidities which can modify survival as well as other clinical parameters. The aim of this study was to evaluate prognostic significance of the National Comprehensive Cancer Network International Prognostic Index (NCCN-IPI), absolute lymphocyte count (ALC), absolute monocyte count (AMC), lymphocyte-to-monocyte ratio (LMR) and comorbidities expressed with Charlson Comorbidity Index (CCI). A total of 182 DLBCL patients 60 years old and older were included, focusing on whole group and patients older than 70. All patients were treated with immunochemotherapy.Overall treatment response was achieved in 84.6% of patients. The NCCN-IPI was of highly prognostic value in the analyzed group (p<0.0001). Survival analysis showed that ALC>1.1x109/L, AMC≤0.59x109/L, and LMR>2.8 were associated with more favorable outcome (p=0.029, p=0.019, p=0.028, respectively). The patients with CCI≥2 had poorer outcome (p=0.008) compared to the patients with CCI 0-1. Multivariate analysis showed that among ALC, AMC, LMR, NCCN-IPI and CCI, the NCCN-IPI was the critical parameter that significantly affected survival (p<0.0001). Furthermore, comorbidities were also valuable independent factors which influenced survival (p=0.031) as well as the ALC (p=0.024). In elderly DLBCL patients, NCCN-IPI and ALC proved their prognostic validity, while poorer outcome could be expected in older patients with high CCI (≥2). Furthermore, mentioned prognostic parameters retained their prognostic value in the group of patients older than 70.

Abstract P2-16-23: The ENCHANT-1 trial (NCT01677455): An open label multicenter phase 2 proof of concept study evaluating first line ganetespib monotherapy in women with metastatic HER2 positive or triple negative breast cancer (TNBC)

Background: Hsp90 is a molecular chaperone protein required for the stabilization and activation of many proteins, referred to as Hsp90 ‘clients’, such as HER2, HIF1-a, EGFR, ER, PI3K, AKT, P53 and VEGFR. The drug candidate, ganetespib is a novel triazolone inhibitor of Hsp90, with over 700 patients treated to date. Ganetespib has shown activity in preclinical models of HER2+, ER+/PR+ and TNBC. Early clinical trials documented ganetespib single agent activity in heavily pretreated HER2+ and TNBC patients. Ganetespib has been well tolerated in clinical trials with a favorable safety profile. This efficacy-screening study is designed to provide further evidence of ganetespib activity and identify potentially predictive biomarkers in metastatic breast cancer (BC).

Methods: The ENCHANT-1 Trial is an international, first-line 2-cohort Phase 2 study in BC patients: Cohort A, HER2 amplified (n = 35), and Cohort B, TNBC (n = 35). Patients who present with previously untreated metastatic disease are eligible for treatment with ganetespib at 150 mg/m2 twice weekly on 3 out of 4 wks, for a total of up to 12 wks. Primary endpoint: ORR assessed using RECIST1.1 criteria. Key secondary endpoints include metabolic response as assessed by PET/CT at wk 3 utilizing modified EORTC criteria. Disease progression (PD) at wk 3 by PET imaging indicates discontinuation of study therapy, and is performed to quickly offer patients with metabolic PD a standard of care treatment.

The study is designed as Simon 2-stage requiring at least one OR in 15 patients for the respective cohort to expand to 35 patients. A Steering Committee is established to oversee the overall study and review the interim results.

Results: The study was initiated in 23 centers globally. At the time of submission, a total of 17 patients had been enrolled; TNBC (n = 15) and HER2 (n = 2). Here we report the interim analysis in the TNBC cohort. The median age was 54 years (range 30 -77) with ECOG PS 0 (n = 7/15). Most patients (n = 9) presented with de novo metastatic disease. 5 patients were not evaluable for PET assessment (3 had not yet reached wk 3 and 2 withdrawn before wk 3 for clinical progression), and 9 patients were not evaluable for objective response at wk 6 (3 withdrawn before or at wk 3 for clinical progression and 6 had not yet reached wk 6 evaluation). In the 10 patients with evaluable PET imaging, 9 patients achieved metabolic (m) response (2 mPR, 4 mSD with dominant tumor shrinkage and 3 SD) and one patient with mPD. In the 6 patients evaluable for OR at wk 6, one patient achieved PR, 2 SD and 3 PD. Treatment with ganetespib was well tolerated; the most common AEs were mild or moderate diarrhea (8/15, 53%), fatigue (5/15, 33%), decreased appetite (4/15, 27%), insomnia (4/15, 27%), and nausea (4/15, 27%).

Conclusion: Ganetespib single agent was generally well tolerated and showed anti-tumor activity TNBC patients as early as 3 weeks following treatment. PET seems to be a good tool to screen antitumor activity of new agents in early settings rather that in heavily pretreated patients. The TNBC cohort has met the protocol criteria for proceeding to stage 2.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-16-23.

Transcranial Doppler in brain death confirmation in clinical practice

PURPOSE

Transcranial Doppler (TCD) can be used as a confirmatory test in brain death. The aim was to present the usefulness of TCD in brain death confirmation.

MATERIALS AND METHODS

Forty-four patients with severe brain lesions leading to brain death were treated over a 4-year period. After the clinical diagnosis of brain death was made, the appropriate confirmatory test was chosen according to patient condition, taking into consideration the restrictions of the test protocol. Due to the inconclusive test results, some patients underwent repeat testing.

RESULTS

Among 44 patients, 19 had neurotrauma, 11 massive aneurysmal subarachnoidal hemorrhages, 1 arteriovenous subarachnoidal and parenchymal hemorrhage, 12 hypertensive parenchymal hemorrhages, and 1 ischemic stroke. As a primary test, TCD was used in 30, brain scintigraphy in 2, multislice CT angiography (CTA) in 10, and cerebral angiography in 2 patients, and the diagnosis was confirmed in 26, 3, 9 and 2 patients, respectively. Due to inconclusive results CTA was repeated in five patients. In patients in whom TCD was applied, the time to confirm the diagnosis was the shortest, and in most (61 %) cerebral circulatory arrest was confirmed within 2 hours of clinical diagnosis.

CONCLUSION

TCD is a favorable confirmatory test for cerebral circulatory arrest in brain death diagnosis.

Distinguishing Parkinson's disease and essential tremor with transcranial sonography

OBJECTIVES

Until today there is no reliable test that can clearly distinguish Parkinson's disease (PD) from the essential tremor (ET). Our aim was to determine the usefulness of the transcranial sonography (TCS) in the differential diagnosis of the PD and ET as well as the interobserver reliability for this method.

METHODS

Transcranial sonography of substantia nigra and clinical examination were performed on 80 PD patients, 30 ET patients, and 80 matched controls by two independent physicians.

RESULTS

Bilateral SN hyperechogenicity over the margin of 0.20 cm(2) was found in 91% of PD patients, 10% of healthy subjects, and in 13% patients with ET. Interobserver agreement for this method was significant (Student's t-test, P = 1.000).

CONCLUSIONS

Substantia nigra hyperechogenicity on TCS is a highly specific finding of PD, where in healthy individuals or in ET patients, it might correspond to an increased risk of developing PD later in life or might also be because of the impairment of nearby area of nucleus ruber in ET patients, as suggested by positron emission tomography studies. TCS may serve as a practical and sufficiently sensitive neuroimaging tool in PD diagnoses and in distinguishing it from ET; its repeatability and accuracy might add to its practical value.

Validation of test-day models for genetic evaluation of dairy goats in Norway

Test-day data for daily milk yield and fat, protein, and lactose content were sampled from the years 1988 to 2003 in 17 flocks belonging to 2 genetically well-tied buck circles. In total, records from 2,111 to 2,215 goats for content traits and 2,371 goats for daily milk yield were included in the analysis, averaging 2.6 and 4.8 observations per goat for the 2 groups of traits, respectively. The data were analyzed by using 4 test-day models with different modeling of fixed effects. Model [0] (the reference model) contained a fixed effect of year-season of kidding with regression on Ali-Schaeffer polynomials nested within the year-season classes, and a random effect of flock test-day. In model [1], the lactation curve effect from model [0] was replaced by a fixed effect of days in milk (in 3-d periods), the same for all year-seasons of kidding. Models [2] and [3] were obtained from model [1] by removing the fixed year-season of kidding effect and considering the flock test-day effect as either fixed or random, respectively. The models were compared by using 2 criteria: mean-squared error of prediction and a test of bias affecting the genetic trend. The first criterion indicated a preference for model [3], whereas the second criterion preferred model [1]. Mean-squared error of prediction is based on model fit, whereas the second criterion tests the ability of the model to produce unbiased genetic evaluation (i.e., its capability of separating environmental and genetic time trends). Thus, a fixed structure with year (year, year-season, or possibly flock-year) was indicated to appropriately separate time trends. Heritability estimates for daily milk yield and milk content were 0.26 and 0.24 to 0.27, respectively.

Aortic arch dissection presenting with hemodynamic spectrum of aortic regurgitation on transcranial Doppler

The diagnosis of aortic dissection is frequently missed at the time of hospital admittance. Neurological presentations are rare, and neuro-sonography is rarely used. We describe a patient with atypical clinical presentation of aortic arch dissection in whom neuro-sonological investigations showed a "cathedral like" haemodynamic spectrum of aortic regurgitation, directing the investigation towards the diagnosis.

Hypoxia-inducible factor-1alpha is an intrinsic marker for hypoxia in cervical cancer xenografts

The hypoxia-inducible factor 1 (HIF-1) is known to induce the expression of several proteins linked to the maintenance of oxygen homeostasis, cellular energy metabolism, and tumor progression. Its alpha subunit (HIF-1alpha) is stabilized under hypoxic conditions and, therefore, might represent an intrinsic marker for tissue hypoxia. Here we report on the spatial relationship between HIF-1alpha and the nitroimidazole hypoxia marker EF5 in cervical carcinoma xenografts, and on their spatial relationship to tumor blood vessels. EF5 was administered to mice bearing ME180 and SiHa cervical cancer xenografts. Frozen tumor tissue sections, triple-stained for HIF-1alpha, the endothelial cell marker CD31, and EF5, were imaged using wide-field multiparameter immunofluorescence microscopy. Expression levels of EF5 and HIF-1alpha were similar in ME180 xenografts, but the percentage of tumor area stained with EF5 was significantly smaller than the percentage of HIF-1alpha-positive area in SiHa tumors. In both tumor types the EF5-HIF-1alpha overlap was statistically significant, thus confirming their spatial and temporal colocalization. Spatial distribution analysis of EF5 and HIF-1alpha is consistent with different pO2 value "thresholds" for EF5 binding and HIF-1alpha expression. Summarized, our results indicate that HIF-1alpha is a useful intrinsic marker for hypoxia in cervical carcinoma xenografts.

Differential effects of buthionine sulphoximine in hypoxic and non-hypoxic regions of human cervical carcinoma xenografts

BACKGROUND AND PURPOSE

Recently we reported increased glutathione (GSH) levels in hypoxic regions of ME 180 and SiHa cervical cancer xenografts. Since this association might act synergistically to protect from radiotherapy, we examined the differential effects of the GSH depleting agent buthionine suiphoximine (BSO) in relation to tumor oxygenation.

MATERIALS AND METHODS

The nitroimidazole EF5 was used to label tumor hypoxia. GSH levels were determined in cryostat sections using a sensitive HPLC assay and in parallel sections using fluorescence image analysis. Using a dual-labeling method, GSH levels were determined selectively in hypoxic and non-hypoxic tumor regions.

RESULTS

GSH levels were higher in hypoxic than in non-hypoxic regions of cervical carcinoma xenografts. Treatment with BSO produced a more pronounced GSH depletion in regions of hypoxia, resulting in similar post-treatment levels in hypoxic and non-hypoxic areas.

CONCLUSIONS

BSO effectively depletes GSH in hypoxic microregions of tumors. These findings suggest a potential role for BSO as an adjunct to radiotherapy in cervical cancer patients.

Imaging of whole tumor cut sections using a novel scanning beam confocal fluorescence MACROscope

Hypoxia caused by inadequate structure and function of the tumor vasculature has been found to negatively determine the prognosis of cancer patients. Hence, understanding the biological basis of tumor hypoxia is of significant clinical interest. To study solid tumor microenvironments in sufficient detail, large areas (several mm in diameter) need to be imaged at microm resolutions. We have used a novel confocal scanning laser MACROscope (CSLM) capable of acquiring images over fields of view up to 2cm x 2cm. To demonstrate its performance, frozen sections from a cervical carcinoma xenograft were triple labeled for tissue hypoxia, blood vessels and hypoxia-inducible transcription factor 1 alpha (HIF-1alpha), imaged using the CSLM and compared to images obtained using a standard epifluorescence microscope imaging system. The results indicate that the CSLM is a useful instrument for imaging tissue-based fluorescence at resolutions comparable to standard low-power microscope objectives.

Protection from radiation-induced DNA single-strand breaks by induction of nuclear metallothionein

PURPOSE

To examine the extent to which nuclear metallothionein protects from radiation-induced DNA damage under aerobic and hypoxic conditions.

MATERIALS AND METHODS

A semiquantitative fluorescence image analysis method measured the nuclear content of metallothionein (MT) in ME180 and SiHa human squamous cervical carcinoma cell lines under normal growth conditions, and following MT induction by zinc. The extent of initial DNA damage following 60Co irradiation under aerobic and hypoxic conditions was assessed using the alkaline comet assay.

RESULTS

Provided that cells were maintained at 37 degrees C, most of the cellular content of MT was in the nucleus. Incubation at 4 degrees C caused the rapid translocation of MT from the nucleus into the cytoplasm in both cell lines, with no net loss of cellular MT. Baseline nuclear MT levels were about four times greater in ME180 cells, and were much more readily induced by treatment with 100 microM zinc acetate, compared with SiHa cells. Under aerobic conditions, MT induction by zinc resulted in no protection in either of the cell lines. Under hypoxic conditions, however, the number of DNA single-strand breaks in zinc-treated cells was reduced by approximately 40% in ME180, but not in SiHa cells, when compared with non-induced controls.

CONCLUSIONS

Nuclear MT can exert a significant level of protection from radiation by a mechanism that involves competition with oxygen for DNA radical sites and/or scavenging of free radicals. Because increased MT levels have been reported in hypoxic micro-regions of some solid tumours, this protective mechanism might have clinical relevance.

Microregional heterogeneity of non-protein thiols in cervical carcinomas assessed by combined use of HPLC and fluorescence image analysis

Under low oxygen conditions, non-protein thiols (NPSHs, non-protein sulfhydryls) can effectively compete for DNA radicals sites and hence represent a potentially important cause of radiation resistance in the clinic. Intra- and intertumoral heterogeneity of glutathione (GSH) and cysteine were assessed in cryostat sections of multiple biopsies obtained from 10 cervical carcinomas by the combined use of a sensitive high-performance liquid chromatography (HPLC) method and a fluorescence image analysis technique to examine the spatial distribution of NPSHs in tumor tissue. Glutathione concentrations ranged from 1.98 to 4.42 mM; significant (> or =1 mM) concentrations of cysteine, a more effective radioprotector than GSH, were found in some tumors. By HPLC, the intratumoral heterogeneity of NPSHs was relatively small compared with the intertumoral heterogeneity. The histochemical stain 1-(4-chloromercuryphenoylazo)-2-napthol (mercury orange), which binds to GSH and cysteine, was used to determine the spatial distribution of NPSHs in tumor tissue. A comparison of NPSH levels in serial cryostat sections showed a close correlation between NPSH values determined by HPLC and mercury orange fluorescence quantification. Using fluorescence image analysis, an approximately 2-fold increase of NPSHs in tumor versus nonmalignant tissue was observed in the same section. Because some cervical carcinomas contain radiobiologically important levels of cysteine, agents that target the biochemical pathways maintaining tumor cysteine have therapeutic potential as adjuncts to radiotherapy in cervix cancer patients.

Influence of low pH on cytotoxicity of paclitaxel, mitoxantrone and topotecan

The extracellular pH (pHe) of solid tumours is often lower than in normal tissues, and this may influence the uptake and/or activity of anti-cancer drugs. The cytotoxicity of mitoxantrone, paclitaxel and topotecan was therefore assessed at low pHe and after manipulation of intracellular pH (pHi) in murine EMT6 and in human MGH-U1 cells. The cytotoxic efficacy of all three agents was reduced at pHe 6.5 as compared with pHe 7.4. The ionophore nigericin and inhibitors of membrane-based ion exchange mechanisms that regulate pHi (5-[N-ethyl-N-isopropyl] amiloride, EIPA; 4,4-diisothiocyanstilbene 2,2-disulphonic acid, DIDS) were used to cause intracellular acidification. Combined use of the cytostatic drugs with pHi modifiers reduced their cytotoxicity under both physiological and low-pHe conditions. The uptake into cells of mitoxantrone (a weak base) was inhibited at pHe 6.5 as compared with pHe 7.4, and smaller effects of low pHe to inhibit uptake of topotecan were also observed. DNA analysis of cell cycle distribution revealed that intracellular acidification, as observed during incubation at low pHe and/or using pHi modifiers, resulted in accumulation of cells in G1 phase, where they may be more resistant to these drugs. Reduced uptake of weak bases (mitoxantrone) at low pHe and altered cell cycle kinetics upon acidification are the postulated causes of reduced cytotoxicity of the agents investigated.