Utility of irritable bowel syndrome subtypes and most troublesome symptom in predicting disease impact and burden

BACKGROUND

Little is known about the characteristics of individuals with irritable bowel syndrome (IBS) according to stool subtype or the most troublesome symptom reported by the individual, or whether these are useful in predicting the impact of IBS.

METHODS

We collected demographic, gastrointestinal, and psychological symptoms, healthcare usage and direct healthcare costs, impact on work and activities of daily living, and quality of life data from individuals with Rome IV-defined IBS.

KEY RESULTS

We recruited 752 people with Rome IV IBS. Individuals with IBS-D reported a poorer disease-specific quality of life than those with IBS-C or IBS-M (mean (SD) IBS-QOL 45.3 (23.0) for IBS-D, vs. 52.3 (19.9) for IBS-C, vs. 49.4 (22.0) for IBS-M, p = 0.005). Mean (SD) IBS-QOL scores were also lower amongst those who reported diarrhea (44.8 (22.3)) or urgency (44.6 (22.3)) as their most troublesome symptom, compared with those reporting abdominal pain (52.2 (22.9)), constipation (49.5 (21.8)), or abdominal bloating or distension (50.4 (21.3)). However, there were no differences in mean EQ-5D scores, IBS severity, levels of anxiety, depression, somatoform symptom-reporting, or gastrointestinal symptom-specific anxiety. Direct healthcare costs of IBS were similar across all subtypes and all most troublesome symptom groups, although some differences in work productivity and social leisure activities were detected.

CONCLUSIONS AND INFERENCES

There appears to be limited variation in the characteristics of individuals with Rome IV IBS based on both stool subtypes and most troublesome symptom reported, suggesting that gastrointestinal symptoms alone have limited ability to predict disease impact and burden.

The future of clinical trials-is it virtual?

INTRODUCTION

Participant recruitment to clinical trials is often sub-optimal. Decentralized clinical trials have the potential to address challenges in traditional site-based clinical trial recruitment.

SOURCES OF DATA

This review is based on recently published literature and the experience of running a large industry-sponsored interventional trial using both traditional and decentralized methods.

AREAS OF AGREEMENT

Efficient delivery of clinical trials is essential to continue to provide therapeutic improvements in a timely and cost-efficient way. Clinical trial designs are constantly evolving to achieve effective trial delivery, manage the complexity of new therapeutic algorithms and conform to cultural developments.

AREAS OF CONTROVERSY

Digitally innovative decentralized clinical trials may be a solution to improve recruitment and retention. Although many trials incorporate digital innovations to reduce patient burden, decentralized clinical trials allow remote access to clinical research, potentially enhancing geographical diversity as well as reducing participant burden.

GROWING POINTS

Areas for development currently being discussed are developing a 'recruitment platform' that exploits the reach of digital connectivity, automated identification of eligible participants from volunteers, employing technology for remote interaction and exploring the logistic process of delivering the interventions.

AREAS TIMELY FOR RELEVANT RESEARCH

The focus of development must ensure that the overall impact will widen participation and reduce inequalities in healthcare.

Willingness to pay for medications among patients with Rome IV Irritable Bowel Syndrome

BACKGROUND

Little is known about willingness to pay for medications among individuals with irritable bowel syndrome (IBS).

METHODS

We collected demographic, gastrointestinal symptom, psychological health, quality of life, and healthcare usage data from 752 adults with Rome IV-defined IBS. We examined willingness to pay for a hypothetical medication in return for improvement in IBS symptoms using a contingent valuation method, according to these variables.

RESULTS

The median amount of money individuals was willing to pay was £1-£50 (IQR £0-£100) per month for a medication with a 100% chance of improving IBS symptoms. Women, compared with men, (92.7% willing to pay "£0," 89.8% "£1-£50," 87.3% "£51-£100," 78.9% "£101-£200," and 78.5% "more than £200," p = 0.008) were less likely to be willing to pay for a pill with a 100% chance of improving IBS symptoms whilst those with an annual income of £30,000 or more (12.2% willing to pay "£0," 25.2% "£1-£50," 33.5% "£51-£100," 40.2% "£101-£200," and 35.1% "more than £200," p = 0.002) were more likely. We observed a higher willingness to pay among those with lower IBS-related quality of life (p = 0.002 for trend). Of all 752 individuals, 92.7%, 74.5%, and 58.0% would be willing to pay for a medication that would give them a 100%, 50%, or 30% chance of improving IBS symptoms, respectively.

CONCLUSION

Patients with IBS are willing to pay for medications which improve IBS symptoms. Future studies should investigate the relative importance of medication pricing, efficacy, and side effect profile among individuals with IBS.

OC-052 A CHANGE IN PRESENTATION OF PARAOESOPHAGEAL HIATUS HERNIA REQUIRING SURGICAL INTERVENTION IN A DISTRICT GENERAL HOSPITAL IN THE NORTHERN REGION OF THE UNITED KINGDOM

Aim

The incidence of paraoesphageal hiatus hernia (PEH) has changed over the last several years. This study aims to ascertain the difference in the presentation of PEH requiring operative intervention at our unit because of the COVID-19 pandemic

Material & Methods

We conducted a retrospective review of procedures performed by a single surgeon for PEH in a district general hospital. We compared cases from 2016 to March 2020 and during the initial period of the COVID-19 pandemic in 2020.

Results

39 consecutive cases were identified undergoing PEH related procedures. The median age was 66 (IQR 26), with slight female predominance (M:F ratio of 5:6). 28 cases (71.8%) were performed as elective cases.

After the 2020 March lockdown, there were 10 cases of PEH repair performed with 78% performed as emergency procedures, compared to 30 cases in the preceding 5 years and 10% performed as emergency cases. Chi-square test to examine the association between COVID-19 pandemic and emergency procedure, X2(1, N=39)=14.199, p=0.000164.

Pre-COVID19 the types of procedures included 76.7% were fundoplication with suture crural closure, 10% were fundoplication with mesh repair, 3.3% biological mesh repair, 3.3% with suture closure of the crural and 6.7% had suture gastropexy. During the COVID-19 period, 44.4% were gastropexy, 33.3% were gastrostomy tube insertion and 22.2% fundoplication performed.

Conclusion

We have seen significantly more emergency PEH related procedures performed and using a variety of procedures. This leads to the consideration of whether current emergency general surgery training can equip trainees for future independent practice.

Impact of Rome IV irritable bowel syndrome on work and activities of daily living

BACKGROUND

Few studies have demonstrated the impact of irritable bowel syndrome (IBS) on work and activities of daily living.

METHODS

We collected demographic, gastrointestinal symptom, psychological health and quality of life data from 752 adults with Rome IV-defined IBS. We used the work productivity and activity impairment questionnaire for irritable bowel syndrome and the work and social adjustment scale to examine the degree of both impairment at work and in activities of daily living, as well as factors associated with these.

RESULTS

Of 467 individuals who were employed, 133 (28.5%) reported absenteeism, 373 (85.6%) presenteeism and 382 (81.8%) overall work impairment. A mean of 1.97 hours of work per week was lost due to IBS. Extrapolating this across the entire UK, we estimate that between 72 and 188 million hours of work are lost per year due to IBS in individuals of working age. Among all 752 participants, 684 (91.0%) reported any activity impairment with 220 (29.3%) reporting impairment in home management, 423 (56.3%) in social leisure activities, 207 (27.5%) in private leisure activities, and 203 (27.0%) in maintaining close relationships. Severe IBS, higher levels of anxiety, depression, somatization and gastrointestinal symptom-specific anxiety, and lower levels of IBS-related quality of life were associated with impairment in both work and activities of daily living.

CONCLUSION

Patients with IBS experience a substantial impact on their work and activities of daily living because of their IBS. Future studies should assess the impact of medical interventions on the ability to work and participate in social activities.

Direct healthcare costs of Rome IV or Rome III-defined irritable bowel syndrome in the United Kingdom

BACKGROUND

Previous studies have demonstrated a substantial economic impact of irritable bowel syndrome (IBS).

AIMS

To provide contemporaneous estimates of direct healthcare costs of IBS in the United Kingdom.

METHODS

We collected demographic, gastrointestinal and psychological symptoms, quality of life and healthcare usage data from adults with Rome IV or Rome III IBS in the United Kingdom. We calculated the mean annual direct healthcare costs of IBS per person and used contemporaneous IBS prevalence data, together with census data, to estimate annual direct costs of IBS. We also examined predictors of higher costs.

RESULTS

The mean annual direct cost of IBS per person among 752 individuals with Rome IV IBS was £556.65 (SD £1023.92) and £474.16 (SD £897.86) for 995 individuals with Rome III IBS. We estimate the annual direct healthcare cost of IBS in the United Kingdom is £1.27 billion if the Rome IV criteria are used to define IBS, and £2.07 billion using Rome III. Among individuals with Rome IV IBS, mean annual costs were higher in those with opiate use (£907.90 vs £470.58, p < 0.001), more severe symptoms (p < 0.001 for trend), a shorter duration of IBS (1 year, £1227.14 vs >5 years £501.60, p = 0.002), lower quality of life (p < 0.001 for trend), and higher depression, somatisation and gastrointestinal symptom-specific anxiety scores (P < 0.001 for trend for all).

CONCLUSION

We estimate annual direct healthcare costs of IBS of between £1.3 and £2 billion in the United Kingdom.

Editorial: risky business. What do sufferers' perceptions of risk from interventions for IBS really mean? Authors' reply

This article is linked to Goodoory et al papers. To view these articles, visit https://doi.org/10.1111/apt.16816 and https://doi.org/10.1111/apt.16909

Willingness to accept risk with medication in return for cure of symptoms among patients with Rome IV irritable bowel syndrome

BACKGROUND

Some drugs for irritable bowel syndrome (IBS) have serious side effects.

AIMS

To examine the willingness of individuals with IBS to accept risks with medication in return for symptom cure.

METHODS

We collected demographic, gastrointestinal symptoms, psychological health, quality of life and impact on work and daily activities data from 752 adults with Rome IV-defined IBS. We examined median willingness to accept death in return for cure with a hypothetical medication using a standard gamble, according to these variables.

RESULTS

Participants would accept a median 2.0% (IQR 0.0%-9.0%) risk of death in return for a 98.0% (IQR 91.0%-100.0%) chance of permanent symptom cure. The median accepted risk of death was higher in men (5.0% vs 2.0%, P < 0.001), those with continuous abdominal pain (4.0% vs 1.0%, P < 0.001), more severe symptoms (P = 0.005 for trend), abnormal depression scores (P < 0.001 for trend), higher gastrointestinal symptom-specific anxiety (P < 0.001 for trend), and lower IBS-related quality of life (P < 0.001 for trend). Those willing to accept above median risk of death were more likely to be male (17.1% vs 9.1%, P < 0.001), take higher levels of risks in their daily life (P = 0.008 for trend), and report continuous abdominal pain (53.1% vs 39.4%, P < 0.001), and had higher depression (P = 0.004 for trend) and lower quality of life (P < 0.001 for trend) scores.

CONCLUSION

Patients are willing to accept significant risks in return for cure of their IBS symptoms.

Atypical breasts cancers

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Myoepithelial carcinomas comprise exclusively of tumour cells with myoepithelial differentiation and can be managed through surgical excision with radiotherapy.

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Mucinous carcinomas are difficult to diagnose but important to distinguish as survival rate between the types can vary.

•

Invasive apocrine carcinomas are difficult to diagnose due to the variable presentation and lack of diagnostic criteria.

Introduction

Method

Conclusion

Porcine acellular dermis-based breast reconstruction: complications and outcomes following adjuvant radiotherapy

Background

Acellular dermal matrices (ADM) such as Strattice^TM are increasingly used in UK during implant-based reconstruction. However, there are mixed opinions regarding the compatibility of radiotherapy treatment in pre- and post-reconstructed breasts. The aims of this study are to audit the rates of radiation induced complications in patients who underwent breast reconstruction using Strattice^TM and establish whether there is an association between timing of radiotherapy and complication rates.

Methods

Retrospective data collection was performed for all patients who underwent skin-sparing mastectomy and immediate or delayed Strattice^TM-based reconstruction, and received pre- or post-reconstruction radiotherapy from July 2010 to November 2014.

Results

The age ranged from 33 to 78 years (mean age 51 ± 10.6) with a mean follow-up time of 21 months. There were 25 Strattice^TM-based reconstructions performed. Sixteen had delayed reconstruction, and 9 had skin-sparing mastectomy and immediate reconstruction. There were 4 (16 %) abandoned procedures due to inability to stretch the mastectomy flap secondary to poor skin compliance. Two women (8 %) presented 4 and 9 months later with wound breakdown. One case (4 %) developed severe capsular contracture following radiotherapy post-reconstruction and 1 case (4 %) of implant rupture. There were no episodes of extrusion or implant infection. Overall complication rates were 32 %. The majority (75 %) of complications occurred in breasts reconstructed post-radiotherapy; however, this is not significant when analysed using chi-square (p = 0.43).

Conclusions

Our evidence suggests that there is no difference in complication rates in pre- and post-radiation individuals; this would suggest that implant-based reconstruction using Strattice^TM should not be an absolute contraindication in pre- or post-radiotherapy patients. However, when planning these procedures, it is paramount that the increased risks are emphasised to patients in order to better manage patient expectation in cases where complications arise.

Level of Evidence: Level III, risk / prognostic study.

Left gastric artery aneurysm rupture: a rare cause of retroperitoneal bleeding: a case report

INTRODUCTION

Visceral artery aneurysms are very rare. Patients usually present as emergency secondary to the sudden rupture of the aneurysm or as an incidental finding on ultrasound, MRI or abdominal computed tomography. Among these, splenic artery aneurysms are the most common ones accounting for 60% of all splanchnic aneurysms and gastric and gastroepiploic aneurysms account for only about 4%.

CASE PRESENTATION

We present a 61-year-old Caucasian male previously fit and well, presenting with sudden onset epigastric pain due to retroperitoneal haemorrhage secondary to ruptured left gastric artery aneurysm. Apart from a tender epigastrium, there were no other obvious signs elicited on abdominal examination. He had persistent tachycardia and haemoglobin drop from 10 g/dl to 6.7 g/dl. He underwent a contrast computed tomography which identified the ruptured left gastric artery. The aneurysm was controlled successfully with coil embolisation of the left gastric artery. At three-month follow-up, there was no evidence of the aneurysm.

CONCLUSION

Clinical presentations that do not correlate with examination finding should prompt immediate extensive investigation. The aid of contrast computed tomography and minimally invasive radiological interventional is the key to a fruitful outcome for this very rare entity.

Rectal metastasis from Breast cancer: A rare entity

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In patients with history of Invasive lobular cancer of breast with positive faecal occult blood with or without bowel symptoms should have high clinical suspicion of bowel metastasis.

•

Breast cancer is the second most common cancer to metastasise to anywhere along the gastrointestinal tract from oropharynx to anus.

Introduction

Breast cancer metastases occurs in around 50% of all presentation. It is the second most common type of cancer to metastasise to the GI tract but this only occurs in less than 1% of cases.

Presentation of case

We report a case that underwent treatment for invasive lobular cancer (ILC) of the breast and 5 years later was found to have rectal and peritoneal metastasis. She is currently receiving palliative management including chemotherapy in the form of weekly Paclitaxel (Taxol^®) and stenting to relieve obstruction.

Conclusion

There should be high clinical suspicion of bowel metastasis in patients presenting with positive faecal occult blood with or without bowel symptoms even if the incidence is less <1% of metastases, particularly in cases where the initial breast tumour was large, with positive axillary nodes.

Rare breast malignancies and review of literature: A single centres experience

•

Lymphoma of the breast is best managed with chemotherapy rather than surgery.

•

Supradiaphragmatic metastases of ovarian cancer to breast can significantly alter prognosis.

•

Osteosarcoma requires total excision with adequate margins in order to determine tumour size which is a valuable prognostic factor for survival.

•

Immunohistochemistry is helpful to distinguish metaplastic carcinoma which are aggressive and are associated with poor outcomes.

•

Adenoid cystic carcinoma of the breast are associated with favourable prognosis that only require surgery.

Introduction

Breast cancer is a heterogeneous condition, with variants which are less common but still very well defined by the World Health Organization (WHO) classification. With the small number of cases each year large trials are difficult to perform. This series aims to discuss the rare breast malignancies encountered within a breast department and the evidence based approached to their management.

Method

Literature search of electronic databases via PubMed and the search engines Google/Google Scholar were used. Emphasis on keywords: breast cancer and the type of histology used to limit search. Searches were screened and those articles suitable had full text versions retrieved. The references to all retrieved texts were searched for further relevant studies.

Conclusion

Due to the rarity of some of these breast cancers, systematic evaluation of patient with detailed histopathology will aid accurate diagnosis and management. The series hopes to add the existing understanding of this small percentage of cases.

Yttrium-90 internal pair production imaging using first generation PET/CT provides high-resolution images for qualitative diagnostic purposes

Yttrium-90 ((90)Y) internal pair production can be imaged by positron emission tomography (PET)/CT and is superior to bremsstrahlung single-photon emission CT/CT for evaluating hepatic (90)Y microsphere biodistribution. We illustrate a case of (90)Y imaging using first generation PET/CT technology, producing high-quality images for qualitative diagnostic purposes.

Comparison of response to radiation, hyperthermia and cisplatin in parental and polymerase beta knockout cells

The role of polymerase beta in response to radiation, cisplatin and hyperthermia was examined in a pair of mouse cell lines, comprising a normal parental line and a derivative with polymerase beta knockout. Cell survival was assessed using the colony survival assay. For irradiation, there was no difference in response between the two cell lines. Treatment with cisplatin for 1 h showed a large increase in resistance in the mutant cell line. The results with hyperthermia were more complex. The mutant was more resistant to 45 degrees C heating, but was slightly more heat sensitive than the wild type at 41 degrees C. Thus, in summary, while the knockout of polymerase beta did not alter radiation sensitivity, it did increase resistance to cisplatin and induced resistance to hyperthermia at higher temperatures (45 degrees C).

Response to pulsed dose rate irradiation with and without mild hyperthermia using tumour and normal cell lines

To determine whether pulsed dose rate irradiation in combination with mild hyperthermia could radiosensitize cells in comparison to pulsed dose rate irradiation alone, human ovarian carcinoma (A2780s, cisplatin- and radiation-sensitive, and A2780cp, cisplatin- and radiation-resistant) and human fibroblast (AG1522) cell lines were used. Cells were irradiated in vitro using two fraction sizes, 0.53 Gy given every hour and 1.6 Gy given every 3h, with an overall average dose rate of 0.53 Gy/h. The data showed that 40 degrees C hyperthermia did not radiosensitize any of the cell lines for the 0.53 Gy every 1 h fractionation scheme. In addition, mild hyperthermia radiosensitized both carcinoma cell lines when using the 1.6 Gy fraction size for all doses tested in the A2780s and at higher doses in the A2780cp, but not the normal cell line. These results suggest a potential clinical advantage when using the 1.6 Gy fraction size with 40 degrees C mild hyperthermia, since hyperthermia radiosensitized the carcinoma cells but not the normal cells.

Evaluation of cell survival, DNA double strand breaks, and DNA synthesis during concurrent camptothecin and X-radiation treatments

We evaluated cell survival, DNA double strand breaks (dsbs), and DNA synthesis following camptothecin (CPT) alone or concurrent CPT and X-radiation treatments in exponential-phase cultures of a radioresistant human melanoma cell line. Cell survival was measured by a clonogenic assay. DNA dsbs were measured by pulsed-field gel electrophoresis. DNA synthesis was measured by incorporation of (3)H-thymidine. We found that (i) concurrent CPT and X-radiation interacted additively, unlike previous results with plateau-phase cultures of these cells, which showed synergistic interaction; (ii) there were strong negative correlations (correlation coefficients of at least 0.82) between clonogenic surviving fractions and DNA dsbs following CPT alone or concurrent CPT and radiation treatments; and (iii) concurrent CPT and radiation (10 Gy) treatment did not completely inhibit DNA synthesis, even though addition of radiation to CPT did further decrease DNA synthesis (relative to CPT alone) at CPT concentrations below 20 microM. Our results suggest that during concurrent CPT and radiation treatment residual DNA dsb levels were good indicators of cell killing and that the absence of complete inhibition of DNA synthesis could at least in part explain the additive interaction between CPT and radiation.

The response of human breast tumour cell lines with altered polymerase beta levels to cisplatin and radiation

MCF 7 (human breast carcinoma cells) and mutants transfected with the DNA polymerase beta gene were tested for response to cisplatin, radiation and combined treatments. The transfected cells showed a higher level of polymerase beta activity and were more resistant to radiation and cisplatin compared to the parental cell line. Further studies showed that for isosurvival treatments the mutant cells were more effective in sublethal radiation damage repair compared to the parental line. The combination of cisplatin with radiation showed effective radiosensitization which was less in the mutants compared to the parental line. In addition, the sequence of cisplatin before irradiation was more effective then cisplabn after irradiation. Pre-exposure to low levels of cisplatin for up to 24 h before irradiation showed a small significant adaptive response in one mutant line at 8 h and while similar trends were observed in the parental lines at earlier times they were not significant. In summary our data show that polymerase beta and thus base excision repair may play a role in cellular responses to cisplatin and radiation.

Equivalence of pulsed-dose-rate to low-dose-rate irradiation in tumor and normal cell lines

To determine whether different fractionation schemes could simulate low-dose-rate irradiation, ovarian cells of the carcinoma cell lines A2780s (radiosensitive) and A2780cp (radioresistant) and AG1522 normal human fibroblasts were irradiated in vitro using different fraction sizes and intervals between fractions with an overall average dose rate of 0.53 Gy/h. For the resistant cell line, the three fractionation schemes, 0.53 Gy given every hour, 1.1 Gy every 2 h, and 1.6 Gy every 3 h, were equivalent to low dose rate (0.53 Gy/h). Two larger fraction sizes, 2.1 Gy every 4 h and 3.2 Gy every 6 h, resulted in lower survival than that after low-dose-rate irradiation for the resistant cell line, suggesting incomplete repair of radiation damage due to the larger fraction sizes. The survival for the sensitive cell line was lower at small doses, but then it increased until it was equivalent to that after low-dose-rate irradiation for some fractionation schemes. The sensitive cell line showed equivalence only with the 1.6-Gy fraction every 3 h, although 0.53 Gy every 1 h and 1.1 Gy every 2 h showed equivalence at lower doses. This cell line also showed an adaptive response. The normal cell line showed a sensitization to the pulsed-dose-rate schemes compared to low-dose-rate irradiation. These data indicate that the response to pulsed-dose-rate irradiation is dependent on the cell line and that compared to the response to low-dose-rate irradiation, it shows some equivalence with the resistant carcinoma cell line, an adaptive response with the parental carcinoma cell line, and sensitization with the normal cells. Therefore, further evaluation is required before implementing pulsed-dose-rate irradiation in the clinic.

Evidence for adaptive response and implication in pulse-simulated low-dose-rate radiotherapy

PURPOSE

Pulsed-dose-rate (PDR) brachytherapy as a substitute for continuous low-dose-rate (LDR) brachytherapy has a number of clinical advantages. However, early results show that some cells can exhibit an adaptive response to radiation and in PDR where many pulses are given such an adaptive response may play an important role in the outcome.

METHODS AND MATERIALS

Nine human cell lines (two normal fibroblast and seven tumor) were evaluated for an adaptive response. Cells were given either a single adapting dose before a challenge dose or given PDR sequences for which the average dose rate matched the LDR dose rate. Response was assessed using the colony survival assay.

RESULTS

Five of the nine cell lines showed an adapting response to single small doses of radiation. Three of these cell lines were further investigated for adapting response to PDR and two of the three lines (one ovarian carcinoma and one glioma) showed an adaptive response which was dependent on pulse size and interval.

CONCLUSION

The data show that an adaptive response can occur in human cells and that it can vary among cell lines. In addition, PDR sequences also produced an adaptive response which could have an affect on PDR therapy if such a response is found in tissues.

Metabolism of alternative substrates and the bioenergetic status of EMT6 tumor cell spheroids

In order to evaluate the ability of EMT6/Ro multicellular spheroids to utilize various pathways of energy production, (13)C and (31)P MRS have been employed to monitor the metabolism of glucose, glutamine, acetate and propionate. EMT6/Ro spheroids perfused with culture medium containing 5.5 mM glucose maintain stable levels of nucleotide triphosphates (NTP) and phosphocreatine (PCr) for up to 48 h, even in the absence of glutamine. The metabolism of 1-(13)C-glucose was almost entirely to 3-(13)C-lactate (88 +/- 12%, n = 7), even though the perfusion medium was equilibrated with 95% O(2). Labeling was also observed in other glycolytic metabolites, primarily alanine and alpha-glycerolphosphate. A low level of (13)C labeling in glutamate, indicative of mitochondrial oxidative metabolism (TCA cycle), was consistently detected when spheroids were perfused with 1-(13)C-glucose, almost exclusively in the C4 position of glutamate. Labeling of glutamate C2 and C3 was always less than 20% of the labeling in C4 and was usually undetectable. No evidence of adjacent carbon labeling in individual glutamate molecules (indicative of multiple cycles of label incorporation) was found, even in high-resolution (13)C NMR spectra of extracts from cells or spheroids. Despite the predominantly glycolytic metabolism of glucose, the mitochondrial substrate glutamine (2 mM, in the presence of < or =0.5 mM glucose from fetal bovine serum), supported stable levels of NTP and PCr in the tumor cells for up to 12 h. In the presence of 2.5 mM acetate, the bioenergetic status of cells in EMT6 spheroids declined slowly but measurably, and no incorporation of label from 2-(13)C-acetate into other metabolites was detected either in intact perfused spheroids or in high-resolution spectra of extracts. In contrast, when the anaplerotic TCA cycle substrate 3-(13)C-propionate replaced acetate, the high-energy phosphate levels in EMT6/Ro spheroids were somewhat reduced, but stabilized at a new lower level. Incubation of spheroids with 3-(13)C-propionate (with natural abundance glucose and glutamine) resulted in label detectable in the C2 and C3 of glutamate, but the primary labeled compound was methylmalonate, an intermediate in propionate metabolism. Addition of vitamin B(12), a cofactor for methylmalonyl CoA reductase, to the growth medium 24 h prior to perfusion with propionate resulted in the elimination of the methylmalonate resonance. A variety of 2- and 3-labeled metabolites were detected, including succinate, malate and glutamate. Labeling of C2 and C3 of lactate implicated cytoplasmic malic enzyme activity.

Comparison of hyperthermia radiosensitization and DNA polymerase inactivation in human normal and melanoma cell lines of different radiosensitivities

Two human melanoma cell lines (one radiosensitive, HT144 and one radioresistant, SK Mel-3) and one normal human fibroblast (AG1522) were evaluated for thermal radiosensitization and the thermal enhancement ratios (TERs) were calculated. These were compared with residual polymerase activity to determine if this activity could be used to predict TERs. In all three cell lines, there was a good correlation between TER and residual polymerase alpha or beta activity. Polymerase beta was more sensitive than polymerase alpha as an indicator for TER. There were small cell line-dependent differences (not related to radiosensitivity) among the correlation curves, indicating that for each cell/tumor-type polymerase activity, vs. TER may have to be calibrated.

p53 status, cellular recovery and cell cycle arrest as prognosticators of in vitro radiosensitivity in human pancreatic adenocarcinoma cell lines

PURPOSE

To investigate the factors contributing to the in vitro radiosensitivity of four human pancreatic adenocarcinoma cell lines differing in p53 status, and the basis for the lack of post-irradiation G1 arrest in the two cell lines that have retained a wild-type p53 allele.

MATERIALS AND METHODS

Cells were X-irradiated and the parameters related to radiosensitivity, as well as the modulation of gene products linked to regulation of cell cycle transit (p53, p21/WAF1/CIP1, pRb) or DNA replication and repair (DNA topoisomerase I and II), were determined.

RESULTS

Both cell lines expressing either mutant (mt) R248W or R273H p53 proteins were more radioresistant. All the cell lines arrested in G2. None of the cell lines arrested in G1 and this was linked to the inability to upregulate p21/WAF1/CIP1. There were no correlations between p53 status and the magnitude or time of maximum G2 arrest. However, there was a negative correlation between a protracted arrest in G2 and the ability to recover from potentially lethal damage (PLD).

CONCLUSIONS

Variation in radiosensitivity is related to p53 status, but the survival advantage conferred by having mutant p53 status is not readily explained neither by recovery from PLD nor by cell cycle arrest kinetics. There is no p53-independent pathway for the recruitment of p21 in these cell lines following irradiation.

Evaluation of cross-resistance between responses to cisplatin, hyperthermia, and radiation in human glioma cells and eight clones selected for cisplatin resistance

Human glioma cells were exposed to stepwise increasing concentrations of cisplatin and given a final, acute, high concentration treatment of cisplatin. From the surviving cells, eight cisplatin resistant clones were selected. These clones demonstrated a range of cisplatin sensitivities that were retained in the absence of cisplatin when cells were continually passaged. These cells were tested for cross-resistance to radiation and hyperthermia at 42 and 45 degrees C. The data showed that seven of the eight clones were also more radioresistant than the parental line, while one was more radiosensitive. The degree of cisplatin resistance was not related to the degree of radiation resistance. For hyperthermia at 42 and 45 degrees C, some of the clones were slightly more resistant than the parental line, while one clone was much more sensitive. This was not the same clone that was radiosensitive. In conclusion, there was no direct correlation between cisplatin resistance, radiation resistance, and hyperthermia response, although some of the clones were resistant to all three treatments.

Bone mineral densities and hip axis lengths of normal Singapore women

This study aims to evaluate the bone mineral densities and hip axis lengths of women in the local population. 227 normal Singapore women of ages 20 to 70 years had evaluation of their bone mineral densities (BMDs) by means of dual X-ray absorptiometry (DXA). The trend of BMDs at the left femoral neck and the lumbar spine remains fairly constant with increasing age until the 45-49 years age-band, beyond which there is a consistent decline. The mean hip axis length is 10.3 cm with a standard deviation of 0.6 cm. In general, the bone mineral densities in the femoral neck and lumbar spine as measured by DXA and the hip axis length of the local population is lower than corresponding figures reported in the Western population.

Comparison of radiosensitization by 41 degrees C hyperthermia during low dose rate irradiation and during pulsed simulated low dose rate irradiation in human glioma cells

PURPOSE

Long duration mild hyperthermia has been shown to be an effective radiosensitizer when given concurrently with low dose rate irradiation. Pulsed simulated low dose rate (PSLDR) is now being used clinically, and we have set out to determine whether concurrent mild hyperthermia can be an effective radiosensitizer for the PSLDR protocol.

MATERIALS AND METHODS

Human glioma cells (U-87MG) were grown to plateau phase and treated in plateau phase in order to minimize cell cycle redistribution during protracted treatments. Low dose rate (LDR) irradiation and 41 degrees C hyperthermia were delivered by having a radium irradiator inside a temperature-controlled incubator. PSLDR was given using a 150 kVp X-ray unit and maintaining the cells at 41 degrees C between irradiations. The duration of irradiation and concurrent heating depended on total dose and extended up to 48 h.

RESULTS

When 41 degrees C hyperthermia was given currently with LDR or PSLDR, the thermal enhancement ratios (TER) were about the same if the average dose rate for PSLDR was the same as for LDR. At higher average dose rates for PSLDR the TERs became less.

CONCLUSIONS

Our data show that concurrent mild hyperthermia can be an effective sensitizer for PSLDR. This sensitization can be as effective as for LDR if the same average dose rate is used and the TER increases with decreasing dose rate. Thus mild hyperthermia combined with PSLDR may be an effective clinical protocol.

Thermal radiosensitization and repair inhibition in human melanoma cells: a comparison of survival and DNA double strand breaks

Human melanoma cells (SK-mel-3) were treated with combinations of radiation and hyperthermia treatment and survival (using the colony forming assay) and DNA double strand breaks (dsb's) (using pulsed field gel electrophoresis) were measured for immediate and delayed plating. The cells were treated in plateau phase, so that delayed plating would result in repair of potentially lethal damage (PLD). Delayed plating showed PLDR for both the survival and the dsb end-point. One hour of heating after irradiation showed a temperature dependent increase in radiosensitization for both the survival endpoint and the dsb endpoint for the temperature range from 42 to 45 degrees C. One hour of heating at 43 degrees C after irradiation resulted in the partial inhibition of PLDR and recovery of dsb's. For heating at 45 degrees C the inhibition of dsb repair was complete. There was good correlation between the survival endpoint and the dsb endpoint for the thermal radiosensitization for both the immediate plating and the PLDR protocols. These data indicate that hyperthermia inhibition of repair of PLD is probably due to the inhibition of dsb rejoining. These correlations were made at the same dose levels for survival and dsb analysis, thus avoiding the potential complications of many earlier studies which used much higher doses for dsb analysis than for survival studies.

Comparison of high dose rate, low dose rate, and high dose rate fractionated radiation for optimizing differences in radiosensitivities in vitro

Radiotherapy is administered with the assumption that all patients respond similarly to radiation although radiosensitivity does vary from patient to patient, resulting in different degrees of early and late effects. Because the dose given to a patient is limited by the response of normal tissue in the treatment field, it would be beneficial to determine the sensitivity of this normal tissue prior to therapy. Previous studies to predict radiosensitivity have used surviving fractions after a single dose given in vitro, however, differences in cell survival at this low level of kill are not easy to resolve. In this study, we set out to evaluate the use of alternative dose regimens which may better resolve differences in radiosensitivity. We have examined several radiation protocols for predictive value, including survival after high doses (6 Gy) at both high (112 cGy/min) and low (.882 cGy/min) dose rates and after fractionated doses of 2 Gy (6 fractions). A sensitive human fibroblast line (S11358) cultured from a patient showing severe effects after therapy is compared with a cell line (OMB1) cultured from an apparently normal subject. Differences between these cell lines have been compared with those between two human melanoma cell lines (SKMEL3 and HT144) which have shown resistant and sensitive response to radiation in vitro respectively. In both fibroblast and melanoma cell lines, the difference in the survival of normal and sensitive cells increased with increasing dose regardless of whether irradiation was delivered as low dose rate, high dose rate, or as fractionated doses. We propose that radiation doses which more closely mimic clinical treatment are more suitable than surviving fraction after 2 Gy (SF2) for in vitro evaluation of relative radiosensitivities of cell populations.

Concomitant treatment with mild hyperthermia, cisplatin and low dose-rate irradiation in human ovarian cancer cells sensitive and resistant to cisplatin

Hyperthermia has been shown to be an effective radiation sensitizer. Cisplatin has also been shown to cause radiosensitization. In part, the sensitization is through the inhibition of repair of radiation damage. In this study we have set out to combine low dose-rate irradiation (during which extensive repair occurs) with both cisplatin and hyperthermia to maximize the radiation sensitizing effect. Two human ovarian carcinoma cell lines, one parental (A2780S) and the other a cisplatin resistant derivative (A2780CP) cell line were used in these experiments. Long duration hyperthermia at 40 degrees C was combined with low concentrations of cisplatin (0.5-3 microg/ml) and low dose-rate irradiation (LDRI). The responses to the individual treatments showed that there was cross resistance in the two cell lines for cisplatin and radiation, but for hyperthermia the opposite effect was found. When all treatments were given concurrently the response was greater than the calculated response of all three individual treatments, indicating a synergistic interaction. The effect was greater in the cisplatin resistant cell line. The combination of mild hyperthermia, low dose cisplatin and LDRI are a good combination for potential clinical application. In addition, this could be a good approach to deal with cisplatin resistance.

Evaluation of apoptosis in four human tumour cell lines with differing sensitivities to cisplatin

Four human tumour cell lines were evaluated for their ability to undergo apoptosis when subjected to cisplatin or hyperthermia treatment. In an ovarian carcinoma line (A2780s) and its derivative cisplatin resistant line (A2780cp) the variation in response was expressed for both the colony survival endpoint and the apoptosis endpoint. Apoptosis was measured by the number of floating cells, DNA agarose gels, and electron microscopy. In fact, cisplatin resistance was expressed to a higher level for apoptosis, than colony survival in the A2780cp cell line compared to the A2780s line. The melanoma cell line (Sk Mel-3) also showed induced apoptosis by cisplatin treatment while the glioma line (U87MG) showed little to no apoptosis in response to cisplatin treatment. Hyperthermia (43 degrees C for 1 hour) induced apoptosis in the human melanoma cell line but not in the glioma cell line. These data indicate that, while both cisplatin and hyperthermia can induce apoptosis in human tumour cell lines, the degree of induction is highly cell line dependent.

DNA topoisomerase I content of a pair of human melanoma cell lines with very different radiosensitivities correlates with their in vitro sensitivities to camptothecin

In this study, we set out to determine if the differential sensitivities to CPT between a radioresistant (Sk-Mel-3) and a radiosensitive (HT-144) human melanoma cell line, and also between cultures with a different growth phase in each cell line, were related to endogenous differences in cellular transport of CPT or to DNA topo I catalytic activities and content. Cultures of HT-144 and Sk-Mel-3 cells in both the exponential, or plateau (i.e. confluent), phase of growth were compared. Cellular response to CPT was determined by clonogenic survival assay. Drug accumulation and efflux were determined using [3H]CPT. Topo I catalytic activity was determined from the ability of nuclear extracts prepared from the cells to relax supercoiled DNA plasmid. Nuclear extracts of the cells were also used to determine topo I content by western blotting. The significantly enhanced sensitivity of exponential-phase, relative to plateau-phase, cultures of both cell lines was related to an enhanced accumulation of [3H]CPT in one (i.e. HT-144), but not the other, cell line. Thus the higher sensitivity of exponential-phase cultures of HT-144 relative to those of Sk-Mel-3 can at least be partially accounted for on the basis of a relatively higher accumulation. However, a higher accumulation was not the reason why plateau-phase cultures of HT-144 were relatively more sensitive than those of Sk-Mel-3. Although there were no significant differences (at the p < 0.05 level) between the endogenous catalytic activities of topo I extracted from exponential- and plateau phase-cultures of both these cell lines, there was a trend for HT-144 cells to show higher endogenous topo I catalytic activities compared to Sk-Mel-3 cells. In contrast, topo I content was higher in exponential- relative to plateau phase-cultures of both cell lines, and in HT-144 relative to Sk-Mel-3 when cultures in a similar growth phase were compared. The relative differences in sensitivity to CPT observed in vitro between these two cell lines, and also between exponential- and plateau phase-cultures of each cell line, correlates best with topo I content rather than topo I catalytic activity or [3H]CPT transport.

Interactions of mild hyperthermia, cisplatin and split dose irradiation in human ovarian carcinoma cells

PURPOSE

Human ovarian cancer cells were evaluated to determine whether combination treatment with mild hyperthermia and cisplatin could inhibit repair of sublethal radiation damage.

MATERIALS AND METHODS

Human ovarian carcinoma cell lines A2780S (parental line) and A2780CP (cisplatin resistant variant) were used in this study. Cisplatin at concentrations of 1 or 3 microg/ml was given concomitantly with 1 h of heating at 40 degrees C either immediately before or after irradiation. Survival was determined using a colony-forming assay.

RESULTS

Neither mild hyperthermia nor cisplatin treatments alone affected sublethal damage repair. The combined treatment showed an effect in both cell lines and was treatment sequence-dependent. The effect was greater in the parental cell line.

CONCLUSIONS

The data show that combined treatment of cisplatin and hyperthermia may have clinical efficacy at cisplatin concentrations and hyperthermia temperatures which by themselves have little to no effect.

Thermotolerance effects on thermoradiosensitization in human glioma cells

Human glioma cells were tested to evaluate thermotolerance (TT) development and its effect on radiosensitization. The data show that long duration mild hyperthermia (LDMH) at 40, 41 and 42 degrees C when given before acute irradiation resulted in increased radiosensitization with heating time. Furthermore, radiosensitization was not reduced by TT. When LDMH was given before 45 degrees C hyperthermia there was evidence of TT development which reduced radiosensitization compared to heating at 45 degrees C alone. For 40 and 41 degrees C heating the effect was maximum for the 8 h heating time while for 42 degrees C it was generally maximum for the 4 h heating time. At longer heating times of 24 to 48 h the effect of TT declined. Thus while LDMH itself does not display TT for radiosensitization it can in fact produce a TT effect on radiosensitization when used in a stepup-heating protocol with 45 degrees C.

Classification of 1H MR spectra of biopsies from untreated and recurrent ovarian cancer using linear discriminant analysis

Proton (1H) magnetic resonance (MR) spectra of ex vivo biopsy samples of ovarian cancers provided biochemical information that was used to discriminate cancer from normal ovarian tissue. Possible differences present in intrinsically resistant tumors or changes in biochemistry after the induction of resistance were identified. Using multivariate techniques, in particular linear discriminant analysis (LDA), ovarian cancer was distinguished from normal ovarian tissue with a sensitivity of 100%, a specificity of 95% and an accuracy of 98%. Moreover, LDA was able to distinguish untreated ovarian cancer from recurrent ovarian cancer with a sensitivity of 92%, a specificity of 100%, and an accuracy of 97%; removal of the single "fuzzy" specimen increased the accuracy to 100%. Applications of this knowledge to in vivo measurements could lead to noninvasive diagnosis of ovarian cancer.

Cisplatin and mild hyperthermia in radiosensitization to low dose rate irradiation in human ovarian carcinoma cells

Two human ovarian carcinoma cell lines, one parental and the other a cisplatin resistant derivative cell line, were evaluated for the efficacy of combined treatments of mild hyperthermia, cisplatin and low dose rate irradiation (LDRI). The data showed that cisplatin (1 or 3 micrograms/ml for 1 hour) combined with mild hyperthermia (40 degrees C for 1 hour) was effective for radiosensitization to LDRI in the parental cell line whether given before or after irradiation. In the cisplatin resistant variant, however, these treatments had little to no effect on LDRI response. Thus these data show that these treatments could be clinically effective if there is no cisplatin resistance. Our previous study showed that concomitant treatments could be effective in both parental and cisplatin resistant cell line (1).

Cell cycle perturbations in cisplatin-sensitive and resistant human ovarian carcinoma cells following treatment with cisplatin and low dose rate irradiation

PURPOSE

To investigate cell cycle pertubations in plateau-phase human ovarian carcinoma cells following treatment with cisplatin, low dose-rate irradiation (LDRI), or combined cisplatin and LDRI, in order to understand cell cycle mechanisms by which these two treatment modalities interact.

METHODS

Human ovarian carcinoma cells sensitive (A2780) and resistant (2780CP) to cisplatin were grown to plateau phase and given protracted cisplatin treatments (A2780 0.7 and 2 microg/ml; 2780CP 5 and 15 microg/ml) and/or LDRI (0.41 cGy/min). Cell cycle distribution following treatment was determined by two-parameter flow cytometry, based on bromodeoxyuridine (BrdU) uptake and DNA content using propidium iodide staining.

RESULTS

The cisplatin-sensitive A2780 cells exposed to cisplatin alone for up to 28 h showed depletion of the G1 fraction and accumulation in S-phase, although the percentage of S-phase cells actively incorporating BrdU dropped to almost zero. The cisplatin-resistant 2780CP cells exposed to cisplatin alone showed a G1 arrest when exposed to 15 microg/ml, but not when exposed to 5 microg/ml. LDRI alone caused little cell cycle redistribution different from controls in either cell line. When LDRI was combined with cisplatin, no significant cell cycle redistribution was observed, apart from a decline in the actively incorporating S-phase fraction.

CONCLUSIONS

Cisplatin caused A2780 cells to accumulate in nonincorporating S-phase, with no evidence of G1 arrest. Cisplatin-resistant 2780CP cells showed a G1 block when exposed to a high enough cisplatin concentration. This could indicate a mechanism of cisplatin resistance in these cells. LDRI alone or in combination with cisplatin did not result in significant cell cycle redistribution.

Cisplatin, hyperthermia and radiation treatment in human cisplatin-sensitive and resistant glioma cell lines

In this study, the effects of mild protracted hyperthermia, combined with prolonged exposure to cisplatin and low dose-rate irradiation (LDRI), were examined in two human cell lines. The cell lines are human glioma parental and cisplatin-resistant variant cells. The results show that mild hyperthermia at 40 degrees C was able to sensitize both the parental and the variant cisplatin-resistant cells to cisplatin treatments (1 microgram/ml for up to 20 h) when the two treatments were given concurrently. When mild hyperthermia and cisplatin were given with LDRI concurrently, additional enhanced cell killing was observed in both the parental and the cisplatin-resistant variant cells. Further analysis of the results showed that when the effects of the trimodality treatment were normalized to the effects of the combined treatment of mild hyperthermia with cisplatin, the residual cell killing was still greater than that observed for radiation alone, indicating a synergistic interaction. This synergistic interaction was greater for the parental line compared to the cisplatin-resistant line. Thus, these data show that the concurrent application of mild hyperthermia, low concentration, long duration, cisplatin and low-dose rate irradiation may be an effective form of treatment in both normally responding and cisplatin-resistant variant human tumour cell lines.

Modelling of continuous low dose rate and accelerated fractionated high dose rate irradiation treatments in a human glioma cell line

The Incomplete-Repair model of Thames in its original and in its two-repair processes forms is used to analyse continuous and fractionated irradiation of a glioma cell line treated in vitro. Furthermore, the Incomplete-Repair model is rederived based on the linear-quadratic model bearing a cubic term. Our results show a potentially enhanced but nonsignificantly improved fit to the data when comparing the cubic to the original form of this model. The repair half-time values showed a decrease, followed by an increase, as a function of small doses (< 1.5Gy) per fraction. This is observed using both the original and the cubic forms of the model. We propose this behaviour to be due to an induced resistance of the repair system followed by a saturation process. Two-repair processes were not seen directly due to the large scatter in the fast and the slow components of repair. Repair half-time values are estimated for various dose per fraction protocols using the original and extended forms of the Incomplete-Repair model. Two-repair processes that are consistent as a function of dose per fraction were not detectable in a glioma cell line treated in vitro.

Cytotoxicity, accumulation, and efflux of cisplatin and its metabolites in human ovarian carcinoma cells

Cisplatin (CP) is one of the most useful antineoplastic drugs. When CP is dissolved in human plasma, different metabolites are formed. Using the OV 2008 human ovarian cancer cell line, we examined the relative cytotoxicities of CP and its metabolites (aquated CP [AP], monomethionine CP [MP], bismethionine CP [BP], and a mixture of CP metabolites in ultrafiltrated human plasma [UP]) in vitro. By clonogenic assay, cell survival (percent of mean +/- SE) of OV 2008 cells exposed for 1 hr to 6.7 microM of CP was 9.8 +/- 0.7 and for its equal platinum contents of AP, MP, BP, and UP solutions were 3.3 +/- 0.7, 9.8 +/- 0.9, 15.9 +/- 1.1, 76.8 +/- 2.1, and 13.1 +/- 0.7, respectively. AP was the most cytotoxic species, and BP was the least cytotoxic species. Cellular platinum uptake (ng/10(6) cells) after addition of 0.33, 1.6, and 2.5 mM of each species for 1 hr was measured and a strong correlation was found between cytotoxicity of each CP metabolite and its corresponding cellular platinum (Pt) uptake (r = 0.997). There was a strong correlation between cytotoxicity of the CP metabolites and their DNA binding. With fractionation of these cells into DNA, nucleoplasm and cytoplasm, the highest platinum content was found on DNA. The most important factor that seems to be responsible for the cytotoxicities of the different CP metabolites is the amount of their associated intracellular accumulation, and particularly the degree of their binding to DNA.

Sequence of treatment is important in the modification of camptothecin induced cell killing by hyperthermia

We investigated the modification of camptothecin (CPT)-induced cell killing by hyperthermia in a radioresistant human melanoma (Sk-Mel-3) and a human normal (AG1522) cell line. CPT, a topoisomerase (topo) I inhibitor, was given as a 1 h exposure at variable doses up to 34 microM; hyperthermia was given either before or following CPT treatment. Hyperthermia was given either as a treatment of 41 degrees C for 8 h (termed lower temperature hyperthermia, LTH) or 45 degrees C for 15 min (termed higher temperature hyperthermia, HTH). LTH preceding CPT treatment had no effect on Sk-Mel-3 but potentiated killing of AG1522 cells. HTH preceding CPT treatment, however, almost completely abrogated the toxicity of CPT to both Sk-Mel-3 and AG1522 cells. These results therefore provided evidence for a lack of enhancement of CPT toxicity towards Sk-Mel-3 cells when hyperthermia preceded treatment with CPT. There was also no potentiation of killing of both cell lines when LTH followed treatment with CPT. In contrast, the killing of Sk-Mel-3 cells was slightly potentiated, whereas that of AG1522 cells was reduced, when HTH followed CPT. These results therefore suggested a potential for enhancement of killing of Sk-Mel-3 relative to AG1522 cells when HTH, but not LTH, followed CPT treatment. In addition, we found that a preceding exposure ot HTH did not affect either accumulation or efflux of[3H]CPT in both cell lines. Thus the significantly reduced cytotoxicity observed under those conditions was not related simply to a modification of accumulation or efflux of CPT. We found no significant differences in the atalytic activities of topo I extracted from the nuclei of Sk-Mel-3 and AG1522 cells that were either heated under HTH conditions or that were no subjected to such treatment. These results therefore suggested that the substantial reduction of cytotoxicity seen when HTH preceded CPT treatment was also not due to an effect on topo I catalytic activity. Our results therefore demonstrate that the sequence of application of hyperthermia and CPT is very important in determining the amount and, possibly, selective potentiation of tumour relative to normal cell cytotoxicity.

Cisplatin and low dose rate irradiation in cisplatin resistant and sensitive human glioma cells

PURPOSE

Human glioma cell lines resistant (U373MGCP) and sensitive (U373MG) to cisplatin were used to evaluate the effect of cisplatin as a sensitizer to low dose rate irradiation (LDRI).

METHODS AND MATERIALS

A cisplatin resistant glioma cell line U373MGCP was developed by chronic exposure of parental U373MG cells to cisplatin. Plateau phase cells were treated with cisplatin, high dose rate (HDR) irradiation (1.12 Gy/min), LDRI (0.0088 Gy/min), or cisplatin concurrent with LDRI. Cell survival was determined by the colony forming assay.

RESULTS

Both cell lines showed increased resistance to radiation at LDR compared with HDR, with Dose Modifying Factors (DMF at 10% survival level) of 1.7 for U373MG and 2.5 for U373MGCP. The increased LDR sparing effect in the cisplatin resistant U373MGCP cells indicates increased repair proficiency. The resistant cell line showed a fourfold increase in resistance to cisplatin cytotoxicity at the 10% survival level compared with the parental U373MG cells. Cisplatin enhanced the response of both cell lines to LDRI. The DMFs were 1.2, 1.2, and 1.7, respectively, for the sensitive U373MG cell line given 1 microgram/ml, and the resistant cell line given 3 or 6 micrograms/ml cisplatin treatments concurrent with LDRI.

CONCLUSIONS

These data show that cisplatin can be an effective sensitizer to LDRI in both cisplatin resistant and sensitive glioma cell lines. However, in the resistant cell line, higher concentrations of cisplatin were necessary to achieve the same level of sensitization as in the sensitive cell line.