INSIGHT 2: a phase II study of tepotinib plus osimertinib in MET-amplified NSCLC and first-line osimertinib resistance.

MET amplification (METamp), a mechanism of acquired resistance to EGFR tyrosine kinase inhibitors, occurs in up to 30% of patients with non-small-cell lung cancer (NSCLC) progressing on first-line osimertinib. Combining osimertinib with a MET inhibitor, such as tepotinib, an oral, highly selective, potent MET tyrosine kinase inhibitor, may overcome METamp-driven resistance. INSIGHT 2 (NCT03940703), an international, open-label, multicenter phase II trial, assesses tepotinib plus osimertinib in patients with advanced/metastatic EGFR-mutant NSCLC and acquired resistance to first-line osimertinib and METamp, determined centrally by fluorescence in situ hybridization (gene copy number ≥5 and/or MET/CEP7 ≥2) at time of progression. Patients will receive tepotinib 500 mg (450 mg active moiety) plus osimertinib 80 mg once-a-day. The primary end point is objective response, and secondary end points include duration of response, progression-free survival, overall survival and safety. Trial registration number: NCT03940703 (clinicaltrials.gov).

Osimertinib is used to treat a type of lung cancer that has specific changes (mutations) in a gene called EGFR. Although tumors will usually shrink (respond) during treatment with osimertinib, they can stop responding, or become resistant, to osimertinib. A common cause of resistance is 'MET amplification', which describes when extra copies of a gene called MET are present. Lung cancer that is resistant to osimertinib due to MET amplification could be treated by combining osimertinib with a treatment that blocks MET, such as tepotinib. INSIGHT 2 is an ongoing study that is designed to learn about the effects and safety of tepotinib combined with osimertinib, in patients with lung cancer that has stopped responding to osimertinib because of MET amplification. A plain language version of this article is available and is published alongside the paper online: www.futuremedicine.com/doi/suppl/10.2217/fon-2021-1406.

Counting mRNA Copies in Intact Bacterial Cells by Fluctuation Localization Imaging-Based Fluorescence In Situ Hybridization (fliFISH).

A method for measuring mRNA copies in intact bacterial cells by fluctuation localization imaging-based fluorescence in situ hybridization (fliFISH) is presented. Unlike conventional single-molecule FISH, where the presence of a transcript is determined by fluorescence intensity, fliFISH relies on On-Off duty cycles of photo-switching dyes to set a predetermined threshold for distinguishing true signals from background noise. The method provides a quantitative approach for detecting and counting true mRNA copies and rejecting false signals with high accuracy.

Regulation of infection efficiency in a globally abundant marine Bacteriodetes virus.

This corrects the article DOI: 10.1038/ismej.2016.81.

Prevalence and predictors of pediculosis capitis among primary school children in Hulu Langat, Selangor.

INTRODUCTION: Pediculosis capitis infestation is endemic in both developing and developed countries leading to various physical, economical and psychological consequences. Our main objective was to determine the prevalence and predictors of pediculosis capitis among primary school children in Hulu Langat District, Malaysia. METHODS: An analytic cross-sectional study using cluster random sampling method was carried out in Hulu Langat District, Malaysia. Self-administered pretested questionnaires were used to collect the data. Hair and scalp examination was also carried out. Multivariate logistic regression was used to control for potential confounding and determine the predictors. RESULTS: The overall mean age of the 1,336 respondents was 9.3 years. Majority were males (52.8%), Malays (79.5%) and 81.3% of the fathers had secondary or tertiary education as compared to 77.3% for the mothers. The overall prevalence of pediculosis capitis was 15.3%. The prevalence of pediculosis was significantly higher among females (28.4%) than males (3.7%, p=0.001). Multivariate logistic regression analysis showed that age 10 years or more (Odds Ratio (OR) = 2.34, 95% Confidence Interval (CI) = 1.673 to 3.272), female gender (OR = 10.26, 95% CI = 6.620 to 15.903), history of contact with an infested person (OR = 2.11, 95% CI = 1.506 to 2.960), Indian compared to Chinese (OR = 3.55, 95% CI = 1.282 to 9.860), Malay to Chinese (OR = 2.59, 95% CI = .994 to 6.774) were associated with pediculosis capitis. CONCLUSIONS: Prevalence of pediculosis capitis among children aged 7 - 12 years in Hulu Langat District was high. There is a need for screening and treatment of pediculosis capitis in primary schools.

Regulation of infection efficiency in a globally abundant marine Bacteriodetes virus.

Bacteria impact humans, industry and nature, but do so under viral constraints. Problematically, knowledge of viral infection efficiencies and outcomes derives from few model systems that over-represent efficient lytic infections and under-represent virus-host natural diversity. Here we sought to understand infection efficiency regulation in an emerging environmental Bacteroidetes-virus model system with markedly different outcomes on two genetically and physiologically nearly identical host strains. For this, we quantified bacterial virus (phage) and host DNA, transcripts and phage particles throughout both infections. While phage transcriptomes were similar, transcriptional differences between hosts suggested host-derived regulation of infection efficiency. Specifically, the alternative host overexpressed DNA degradation genes and underexpressed translation genes, which seemingly targeted phage DNA particle production, as experiments revealed they were both significantly delayed (by >30 min) and reduced (by >50%) in the inefficient infection. This suggests phage failure to repress early alternative host expression and stress response allowed the host to respond against infection by delaying phage DNA replication and protein translation. Given that this phage type is ubiquitous and abundant in the global oceans and that variable viral infection efficiencies are central to dynamic ecosystems, these data provide a critically needed foundation for understanding and modeling viral infections in nature.

Conservation of protein abundance patterns reveals the regulatory architecture of the EGFR-MAPK pathway.

Various genetic mutations associated with cancer are known to alter cell signaling, but it is not clear whether they dysregulate signaling pathways by altering the abundance of pathway proteins. Using a combination of RNA sequencing and ultrasensitive targeted proteomics, we defined the primary components-16 core proteins and 10 feedback regulators-of the epidermal growth factor receptor (EGFR)-mitogen-activated protein kinase (MAPK) pathway in normal human mammary epithelial cells and then quantified their absolute abundance across a panel of normal and breast cancer cell lines as well as fibroblasts. We found that core pathway proteins were present at very similar concentrations across all cell types, with a variance similar to that of proteins previously shown to display conserved abundances across species. In contrast, EGFR and transcriptionally controlled feedback regulators were present at highly variable concentrations. The absolute abundance of most core proteins was between 50,000 and 70,000 copies per cell, but the adaptors SOS1, SOS2, and GAB1 were found at far lower amounts (2000 to 5000 copies per cell). MAPK signaling showed saturation in all cells between 3000 and 10,000 occupied EGFRs, consistent with the idea that adaptors limit signaling. Our results suggest that the relative stoichiometry of core MAPK pathway proteins is very similar across different cell types, with cell-specific differences mostly restricted to variable amounts of feedback regulators and receptors. The low abundance of adaptors relative to EGFR could be responsible for previous observations that only a fraction of total cell surface EGFR is capable of rapid endocytosis, high-affinity binding, and mitogenic signaling.

Functional Status of Post Stroke Survivors

Globally, stroke is the commonest cause of long-term disability. The residual disabilities among post stroke patients affect their daily living activities. The aim of rehabilitation therapy is to help stroke survivors to gain back their functional ability. The present study aimed to determine the relationship between post stroke duration with functionality status of post-stroke survivals at a teaching hospital in Kuala Lumpur. A cross-sectional study involved one hundred nine five post stroke patients who attended the Rehabilitation Clinic over a 4-month period. The data on post stroke duration was reveale from patient’s cleckship. Their functional status was assessed with Modified Barthel Index (MBI). Results showed the mean age of participants was 61 years (SD=13.86, range:22-87 years), with 118 males and 81 females having a median duration of 12 months post-stroke (range: 1–79 months). The prevalence 123 (63.1%) of stroke survivors are found to be dependent in their daily living activity. A Chi-square test for independence indicated there was significant relationship between post-stroke duration with levels of functioning, χ2 (2 , n=195) = 6.455, p<0.05,phi = 0.182. Patients in post-stroke duration of 13-24 months were independent (52.1) than ≤ 12 months and ≥ 24 months.

Inference of interactions in cyanobacterial-heterotrophic co-cultures via transcriptome sequencing.

We used deep sequencing technology to identify transcriptional adaptation of the euryhaline unicellular cyanobacterium Synechococcus sp. PCC 7002 and the marine facultative aerobe Shewanella putrefaciens W3-18-1 to growth in a co-culture and infer the effect of carbon flux distributions on photoautotroph-heterotroph interactions. The overall transcriptome response of both organisms to co-cultivation was shaped by their respective physiologies and growth constraints. Carbon limitation resulted in the expansion of metabolic capacities, which was manifested through the transcriptional upregulation of transport and catabolic pathways. Although growth coupling occurred via lactate oxidation or secretion of photosynthetically fixed carbon, there was evidence of specific metabolic interactions between the two organisms. These hypothesized interactions were inferred from the excretion of specific amino acids (for example, alanine and methionine) by the cyanobacterium, which correlated with the downregulation of the corresponding biosynthetic machinery in Shewanella W3-18-1. In addition, the broad and consistent decrease of mRNA levels for many Fe-regulated Synechococcus 7002 genes during co-cultivation may indicate increased Fe availability as well as more facile and energy-efficient mechanisms for Fe acquisition by the cyanobacterium. Furthermore, evidence pointed at potentially novel interactions between oxygenic photoautotrophs and heterotrophs related to the oxidative stress response as transcriptional patterns suggested that Synechococcus 7002 rather than Shewanella W3-18-1 provided scavenging functions for reactive oxygen species under co-culture conditions. This study provides an initial insight into the complexity of photoautotrophic-heterotrophic interactions and brings new perspectives of their role in the robustness and stability of the association.

Comparison of nested and ELISA based polymerase chain reaction assays for detecting Chlamydia trachomatis in pregnant women with preterm complications.

Identification of pregnant women infected with Chlamydia trachomatis is essential to allow early antibiotic treatment in order to prevent adverse pregnancy outcomes. In this study, two nucleic acid amplification tests (NAAT) namely nested PCR (BioSewoom, Korea) and Amplicor CT/NG (Roche Diagnostic, USA) were evaluated in terms of sensitivity and specificity for the detection of C. trachomatis DNA in pregnant women with preterm complications. A cross-sectional study was carried out in two public hospitals in Southern Selangor, Malaysia. Endocervical swabs obtained were subjected to DNA amplification using nested PCR (BioSewoom, Korea) and Amplicor CT/NG (Roche Diagnostic, USA). A total of 83 endocervical swabs obtained from pregnant women of less than 37 weeks gestation and presented with preterm complications were subjected to chlamydial DNA detection using both assays. The study shows that Amplicor CT/NG assay is more effective in the detection of C. trachomatis DNA from endocervical swabs compared to Biosewoom nested PCR kit. Agreement between the two assays were poor (kappa=0.094) with nested PCR showing a low sensitivity of 10.81% and a 97.83% specificity when compared to Amplicor CT/NG. The results obtained indicated that BioSewoom nested PCR was less sensitive than Amplicor CT/ NG for detecting C. trachomatis in endocervical specimens and that another more reliable test is required for confirmatory result.

Closing the global cancer divide--performance of breast cancer care services in a middle income developing country.

BACKGROUND: Cancer is the leading cause of deaths in the world. A widening disparity in cancer burden has emerged between high income and low-middle income countries. Closing this cancer divide is an ethical imperative but there is a dearth of data on cancer services from developing countries. METHODS: This was a multi-center, retrospective observational cohort study which enrolled women with breast cancer (BC) attending 8 participating cancer centers in Malaysia in 2011. All patients were followed up for 12 months from diagnosis to determine their access to therapies. We assess care performance using measures developed by Quality Oncology Practice Initiative, American Society of Clinical Oncology/National Comprehensive Cancer Network, American College of Surgeons' National Accreditation Program for Breast Centers as well as our local guideline. RESULTS: Seven hundred and fifty seven patients were included in the study; they represent about 20% of incident BC in Malaysia. Performance results were mixed. Late presentation was 40%. Access to diagnostic and breast surgery services were timely; the interval from presentation to tissue diagnosis was short (median = 9 days), and all who needed surgery could receive it with only a short wait (median = 11 days). Performance of radiation, chemo and hormonal therapy services showed that about 75 to 80% of patients could access these treatments timely, and those who could not were because they sought alternative treatment or they refused treatment. Access to Trastuzumab was limited to only 19% of eligible patients. CONCLUSIONS: These performance results are probably acceptable for a middle income country though far below the 95% or higher adherence rates routinely reported by centres in developed countries. High cost trastuzumab was inaccessible to this population without public funding support.

The highly conserved MraZ protein is a transcriptional regulator in Escherichia coli.

The mraZ and mraW genes are highly conserved in bacteria, both in sequence and in their position at the head of the division and cell wall (dcw) gene cluster. Located directly upstream of the mraZ gene, the Pmra promoter drives the transcription of mraZ and mraW, as well as many essential cell division and cell wall genes, but no regulator of Pmra has been found to date. Although MraZ has structural similarity to the AbrB transition state regulator and the MazE antitoxin and MraW is known to methylate the 16S rRNA, mraZ and mraW null mutants have no detectable phenotypes. Here we show that overproduction of Escherichia coli MraZ inhibited cell division and was lethal in rich medium at high induction levels and in minimal medium at low induction levels. Co-overproduction of MraW suppressed MraZ toxicity, and loss of MraW enhanced MraZ toxicity, suggesting that MraZ and MraW have antagonistic functions. MraZ-green fluorescent protein localized to the nucleoid, suggesting that it binds DNA. Consistent with this idea, purified MraZ directly bound a region of DNA containing three direct repeats between Pmra and the mraZ gene. Excess MraZ reduced the expression of an mraZ-lacZ reporter, suggesting that MraZ acts as a repressor of Pmra, whereas a DNA-binding mutant form of MraZ failed to repress expression. Transcriptome sequencing (RNA-seq) analysis suggested that MraZ also regulates the expression of genes outside the dcw cluster. In support of this, purified MraZ could directly bind to a putative operator site upstream of mioC, one of the repressed genes identified by RNA-seq.

Comparison of maternal characteristics in low birth weight and normal birth weight infants.

Low birth weight is a key determinant in the risk of morbidity and mortality in the neonatal period and during childhood. This unmatched case-control study in Hamadan, Islamic Republic of Iran, compared the characteristics of mothers of low- and normal-birth-weight infants. Maternal sociodemographic data, pregnancy history, anthropometric data and cord plasma zinc level were collected from 134 mothers of low-birth-weight infants and 134 mothers of normal infants at the time of delivery. Significant differences in maternal characteristics namely gravida, parity, body mass index, maternal weight gain during pregnancy and plasma cord blood zinc were found between low- and normal-birth-weight infants. There were no significant differences in maternal age, maternal education, maternal occupation, family income, previous abortion, previous preterm labour, birth Iinterval, type of clinic and place of residence between the 2 groups.

Premorbid brain volume estimates and reduced total brain volume in adults exposed to trauma with or without posttraumatic stress disorder: a meta-analysis.

OBJECTIVE: The primary objective of this study was to meta-analytically investigate whether total brain volume (TBV) and total intracranial volume (TICV) differ between adult participants with posttraumatic stress disorder (PTSD) and controls. BACKGROUND: TICV reaches maximum growth by early adolescence and provides an estimate of premorbid brain size. Little work has directly examined TBV in PTSD participants, although limited evidence suggests that deficits in brain volume may occur. METHODS: Using electronic databases, we identified articles containing TBV and TICV data for adult PTSD participants. Data were extracted and effect sizes were calculated. RESULTS: We identified 8 studies with TBV data (105 PTSD participants and 122 trauma-unexposed controls) and 2 studies with TICV data (18 PTSD participants and 25 trauma-unexposed controls). TBV was significantly smaller in PTSD participants compared with trauma-unexposed controls. In contrast, TICV did not differ between these groups. There were no significant differences in TBV and TICV between PTSD and trauma-exposed controls. CONCLUSIONS: TBV is significantly smaller in adult PTSD participants compared with trauma-unexposed controls. TICV did not differ significantly between these groups, suggesting that a deficit in TBV occurred at some point after the attainment of maximum brain volume in the PTSD group.

A randomised controlled trial of peer-adult-led intervention on improvement of knowledge, attitudes and behaviour of university students regarding HIV/AIDS in Malaysia.

INTRODUCTION: The aim of this study was to investigate the knowledge, attitudes and behaviour of university students regarding acquired immunodeficiency syndrome (AIDS) and the human immunodeficiency virus (HIV). METHODS: A randomised controlled trial of 530 university students was done using peer-adult facilitators. Participants completed a questionnaire before and after the intervention, which was a four-hour group session. A prevention programme was developed by local experts, health educators and peer facilitators. The peer-adult-led programme was designed to provide a conceptual model of HIV risk reduction through information, motivational and behavioural skills, a harm reduction module and health promotion theme. RESULTS: The main outcome measured was the level of knowledge, attitudes and behaviour scores. The results suggest that relative to the control group, participants in the intervention group had higher levels of knowledge (30.37 vs. 25.40; p-value is 0.001) and a better attitude (12.27 vs. 10.84; p-value is 0.001). However, there was no difference in the behavioural score (9.47 vs. 9.41; p-value is 0.530). The correlation between the level of knowledge and age and the level of education was found in the intervention group, but not in the control group (p-value is 0.01). Attitude and gender were found to be correlated in the intervention group only (p-value is 0.01). CONCLUSION: Our programme was successful in increasing knowledge and improving attitudes towards AIDS and HIV. However, it did not improve risk-taking behaviour. Peer-adult-led educational programmes for youth using various interactional activities, such as small group discussions, poster activity and empathy exercises, can be successful in changing the prevailing youth perceptions of AIDS and HIV.

Obesity among Mongolian Adults from Urban and Rural Areas.

Shifts in lifestyles and eating patterns have led to an increasing prevalence of chronic non-communicable diseases in the adult population in Mongolia. This article reports the prevalence of obesity, abdominal obesity and body fat among 408 Mongolian adults aged 25 years and above. The subjects included 61.2% from urban areas and 38.8% from rural areas, reflective of the 60: 40 urban rural ratio in the general population. Anthropometric measurements were taken according to standard methods. Classification of overweight/obesity was based on body mass index of WHO while abdominal obesity was based on WPRO for Asians. Men made up 47.8% (200) and women 52.2% (218) of the sample. The mean age of the subjects was 46.7±12.7 years. About one-third (32.8%) of the subjects were overweight and 10.5% obese. A higher proportion of women (13.3%) than men were obese (7.5%). The age groups of 35-54 years in men and 55-64 years in women showed the highest prevalence of overweight. Prevalence of abdominal obesity was found in 46.5% of the men and in 65.1% of the women. Women aged 55-64 years had the highest proportion (78.4%) of abdominal obesity. In terms of body fat, 20.0 % and 51.5% of the men had high and very high levels of body fat respectively, while among the women, 15.1% and 55.5% respectively had high and very high levels of body fat. Mongolian adults face serious risk of cardiovascular diseases and other aspects of ill-health brought about by obesity. Prevention and control of obesity should be targeted as an urgent public health agenda in Mongolia.

Parasitic infections among Orang Asli (aborigine) in the Cameron Highlands, Malaysia.

In April 2004, an outbreak of acute diarrheal illness occurred among the Orang Asli (aborigine) in the Cameron Highlands, Pahang State, Peninsular Malaysia, where rotavirus was later implicated as the cause. In the course of the epidemic investigation, stool samples were collected and examined for infectious agents including parasites. Soil transmitted helminthes (STH), namely Ascaris lumbricoides (25.7%), Trichuris trichiura (31.1%) and hookworm (8.1%), and intestinal protozoa, which included Giardia lamblia (17.6%), Entamoeba histolytica/E. dispar (9.4%), Blastocystis hominis (8.1%) and Cryptosporidium parvum (2.7%), were detected. Forty-four (59.5%) were infected with at least one parasite, 24 (32.4%), 12 (16.2%) and 8 (10.8%) had single, double and triple parasitic infections, respectively. STH were prevalent with infections occurring as early as in infancy. Giardia lamblia, though the most commonly found parasite in samples from symptomatic subjects, was within the normally reported rate of giardiasis among the various communities in Malaysia, and was an unlikely cause of the outbreak. However, heavy pre-existing parasitic infections could have contributed to the severity of the rotavirus diarrheal outbreak.

An emerging role for escitalopram in the treatment of obsessive-compulsive disorder.

Obsessive-compulsive disorder (OCD) is a common and severe neuropsychiatric disorder treated by both behavioral and pharmacologic techniques. Despite the availability of treatments for OCD, including the selective serotonin reuptake inhibitors (SSRIs), many OCD patients have an inadequate response to current treatments. As such, additional approaches to the management of OCD are required. A potential but little studied treatment for OCD is the SSRI escitalopram. Escitalopram is the S-enantiomer of citalopram, the preparation containing both S and R enantiomers of citalopram. Not only is escitalopram the most selective of the SSRIs, it is also devoid of R-citalopram, which may interfere with the effects of the S enantiomer. Escitalopram appears to be effective in depression and several anxiety disorders, including social anxiety disorder and generalized anxiety disorder, conditions in which it also appears reasonably well tolerated. Enantiomeric specificity, high serotonin reuptake selectivity, comparatively good tolerability and favorable pharmacokinetics, and preliminary evidence of efficacy in OCD suggest a potential role for the use of escitalopram in the treatment of OCD. Nevertheless, additional work including evaluating the use of escitalopram with behavioral interventions and in long-term treatment of OCD is needed to clarify its overall role in managing OCD.

Neuroimaging, cognitive, and neurobehavioral outcomes following carbon monoxide poisoning.

Carbon monoxide is a colorless, odorless gas produced as a byproduct of combustion. Carbon monoxide is the leading cause of poisoning injury and death worldwide. Morbidity following CO poisoning includes neurologic sequelae, neuropathologic abnormalities on brain imaging, neurobehavioral changes, and cognitive impairments. It is estimated that as high as 50% of individuals with carbon monoxide poisoning will develop neurologic, neurobehavioral, or cognitive sequelae. Carbon monoxide related cognitive impairments included impaired memory, attention, executive function, motor, visual spatial, and slow mental processing speed. Given the high rate of brain related morbidity and the fact that the majority of carbon monoxide is avoidable, awareness and prevention of carbon monoxide poisoning is warranted.

Deaths in children during an outbreak of hand, foot and mouth disease in Peninsular Malaysia--clinical and pathological characteristics.

From July through December 1997, 11 previously healthy children in Peninsular Malaysia succumbed to an illness clinically characterised by an acute severe refractory left-ventricular failure, following a brief prodromal illness, in the midst of an outbreak of hand, foot and mouth disease (HFMD), similar to the reported experience in Sarawak and Taiwan. Retrospective reviews of the clinical features and results of laboratory, pathological and virological investigations of cases were conducted. The median age of the 11 case-patients was 31 months (range, 13 to 49 months); 6 were males. A brief prodromal illness of 3 days (range, 2 to 5 days) was characterised by fever (axillary temperature > 38 degrees C) (100%), oral ulcers (72%), extremity rashes (45%) and significant vomiting (55%). Upon hospitalisation, 7 of 11 case-patients had features suggestive of cardiogenic shock, while 4 of 11 case-patients developed shock during hospitalisation as evidenced by marked sustained tachycardia (heart rate > or = 180 beats per minute), poor peripheral pulses and peripheral perfusion, mottled extremities, pulmonary oedema (haemorrhagic pulmonary secretions in 8 of 11 cases during tracheal intubation, often precipitated by conservative crystalloid boluses, and radiographic evidence of acute pulmonary oedema in 5 of 7 cases) and markedly impaired left ventricular function on echocardiographic examination (7 of 7 cases). Three of 4 case-patients had aseptic meningitis while one case-patient also had an acute flaccid paraparesis. Despite supportive therapy, death occurred within a median of 13.4 hours following hospitalization. Post-mortem findings (all 8 specimens examined) consistently demonstrated brain-stem encephalitis with foci of neuronal necrosis and micro-abscesses. None of the 11 specimens examined revealed histological evidence of myocarditis. Enterovirus 71 (EV71) was detected in 10 of 11 case-patients, many (7) from various sterile tissue sites (5 from central nervous tissues). No other viruses were isolated or identified. Clinical features and pathological studies closely paralleled the reported experience in Sarawak and Taiwan. The uniform necropsy findings of necrotizing brain-stem encephalitis coupled with essentially normal myocardial histology, in concert with the concurrent and consistent detection of EV71 points to a primary EV71 encephalitis; as yet unclear neurogenic mechanisms may account for the cardiovascular manifestations.

A paracrine signal mediates the cell transformation response to low dose gamma radiation in JB6 cells.

The carcinogenic response to radiation is complex and may involve adaptive cellular responses as well as a bystander effect mediated by paracrine or intercellular signaling activities. Using a newly developed co-culture model we have examined whether low dose gamma radiation induces the transformation of JB6 mouse epidermal cells as well as non-irradiated bystander cells. Cell transformation response is defined as the acquisition of anchorage-independent growth properties and is quantified by counting colonies on soft agar. Exposure of JB6 cells to low dose (2-20 cGy) gamma radiation resulted in an approximate 1.9 +/- 0.1 and 2.8 +/- 0.5-fold increase in cell transformation response when cells were seeded at 1 x 10(4) or 1 x 10(5) cells/dish, relative to respective sham exposed controls. We developed a co-culture model where sham exposed or irradiated JB6 cells were mixed with non-irradiated JB6 cells that had been stably transfected with the enhanced yellow fluorescent protein (EYFP) to enable the distinction of fluorescent bystander-specific colonies. A significant increase in the number of bystander-specific colonies was observed in co-culture with 10 cGy irradiated JB6 cells (224 +/- 9), relative to the number of bystander-specific colonies arising in co-culture with sham exposed JB6 cells (55 +/- 16). Our results indicate that low dose radiation induces the transformation of JB6 cells and that a soluble paracrine factor that is secreted by irradiated cells induces the transformation of non-irradiated bystander cells.