mRNA expression levels and genetic status of genes involved in the EGFR and NF-κB pathways in metastatic non-small-cell lung cancer patients.

BACKGROUND: Metastatic non-small-cell lung cancer (NSCLC) has a dismal prognosis. EGFR is overexpressed or mutated in a large proportion of cases. Downstream components of the EGFR pathway and crosstalk with the NF-κB pathway have not been examined at the clinical level. We explored the prognostic significance of the mRNA expression of nine genes in the EGFR and NF-κB pathways and of BRCA1 and RAP80 in patients in whom EGFR and K-ras gene status had previously been determined. In addition, NFKBIA and DUSP22 gene status was also determined. METHODS: mRNA expression of the eleven genes was determined by QPCR in 60 metastatic NSCLC patients and in nine lung cancer cell lines. Exon 3 of NFKBIA and exon 6 of DUSP22 were analyzed by direct sequencing. Results were correlated with outcome to platinum-based chemotherapy in patients with wild-type EGFR and to erlotinib in those with EGFR mutations. RESULTS: BRCA1 mRNA expression was correlated with EZH2, AEG-1, Musashi-2, CYLD and TRAF6 expression. In patients with low levels of both BRCA1 and AEG-1, PFS was 13.02 months, compared to 5.4 months in those with high levels of both genes and 7.7 months for those with other combinations (P=0.025). The multivariate analysis for PFS confirmed the prognostic role of high BRCA1/AEG-1 expression (HR, 3.1; P=0.01). Neither NFKBIA nor DUSP22 mutations were found in any of the tumour samples or cell lines. CONCLUSIONS: The present study provides a better understanding of the behaviour of metastatic NSCLC and identifies the combination of BRCA1 and AEG-1 expression as a potential prognostic model.

Epidermal growth factor receptor tyrosine kinase inhibitors as first-line treatment in advanced nonsmall-cell lung cancer.

PURPOSE OF REVIEW: Classic activating mutations in the form of deletions in exon 19 or a missense mutation L858R in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) predict dramatic responses to EGFR tyrosine kinase inhibitors such as gefitinib and erlotinib. We review here the clinical benefits of targeted therapy with erlotinib and gefitinib in white and Asian nonsmall-cell lung cancer patients. RECENT FINDINGS: Two separate analyses of pooled data from small phase II prospective studies show that therapy with gefitinib and erlotinib induces responses in over 70% of nonsmall-cell lung cancer patients harboring classic EGFR mutations, with progression-free survival ranging from 9 to 13 months and median survival of around 23 months. Two separate studies in white and Asian patients have recently confirmed that these subgroups of patients attain response rates of 70% with erlotinib and gefitinib, including complete responses, progression-free survival of up to 14 months, and median survival of up to 27 months. The serial monitoring of EGFR mutations in the blood will permit the assessment of molecular responses and be an important tool for the surveillance of clinical progression. SUMMARY: Nonsmall-cell lung cancer with EGFR mutations constitute a new entity with a unique opportunity for further refinement of different genetic subgroups among patients with EGFR mutations, requiring different personalized treatment strategies. Despite the impressive outcomes attained with EGFR tyrosine kinase inhibitors, patients with EGFR mutations at present require continuous treatment, and only a fraction of these patients will reach sustainable long-term survival.

Detection of EGFR mutations with mutation-specific antibodies in stage IV non-small-cell lung cancer.

BACKGROUND: Immunohistochemistry (IHC) with mutation-specific antibodies may be an ancillary method of detecting EGFR mutations in lung cancer patients. METHODS: EGFR mutation status was analyzed by DNA assays, and compared with IHC results in five non-small-cell lung cancer (NSCLC) cell lines and tumor samples from 78 stage IV NSCLC patients. RESULTS: IHC correctly identified del 19 in the H1650 and PC9 cell lines, L858R in H1975, and wild-type EGFR in H460 and A549, as well as wild-type EGFR in tumor samples from 22 patients. IHC with the mAb against EGFR with del 19 was highly positive for the protein in all 17 patients with a 15-bp (ELREA) deletion in exon 19, whereas in patients with other deletions, IHC was weakly positive in 3 cases and negative in 9 cases. IHC with the mAb against the L858R mutation showed high positivity for the protein in 25/27 (93%) patients with exon 21 EGFR mutations (all with L858R) but did not identify the L861Q mutation in the remaining two patients. CONCLUSIONS: IHC with mutation-specific mAbs against EGFR is a promising method for detecting EGFR mutations in NSCLC patients. However these mAbs should be validated with additional studies to clarify their possible role in routine clinical practice for screening EGFR mutations in NSCLC patients.

Utility of p16 immunohistochemistry for the identification of Lynch syndrome.

PURPOSE: Immunohistochemistry for mismatch repair proteins has shown utility in the identification of Lynch syndrome, but majority of tumors with loss of MLH1 expression are due to sporadic hypermethylation of the MLH1 promoter. These tumors can also show epigenetic silencing of other genes, such as p16. The aim of our study is to evaluate the utility of p16 immunohistochemistry in the prediction of MLH1 germline mutations. EXPERIMENTAL DESIGN: p16 immunohistochemistry was appropriately evaluated in 79 colorectal cancers with loss of MLH1 expression. Methylation of MLH1 and p16 were quantitatively studied using real-time PCR assay Methylight. BRAF V600E mutation in tumor tissue was also investigated. Genetic testing for germline mutation of MLH1 was made on 52 patients. RESULTS: Loss of p16 expression was seen in 21 of 79 samples (26.6%). There was found statistically significant association between p16 expression and p16 methylation (P < 0.001), MLH1 methylation (P < 0.001), and BRAF mutation (P < 0.005). All tumors with loss of p16 expression showed hypermethylation of p16 (21 of 21), 95.2% (20 of 21) showed MLH1 methylation, and 71.4% (15 of 21) were mutated for BRAF V600E. Mutational analysis showed pathogenic germline mutations in 8 of the patients, harboring 10 tumors. All 10 of these tumors showed normal staining of p16 in the immunochemical analysis. CONCLUSIONS: p16 immunohistochemistry is a good surrogate marker for p16 and MLH1 epigenetic silencing due to hypermethylation, and is useful as screening tool in the selection of patients for genetic testing in Lynch syndrome.

Low activation of Insulin-like Growth Factor 1-Receptor (IGF1R) is associated with local recurrence in early breast carcinoma.

Background The predictive value of IGF1R on local recurrence in invasive breast carcinoma (BC) is not well known. Methods In a series of 197 lymph-node negative BC patients treated with breast-conserving surgery and radiation therapy, we performed immunohistochemistry for alpha-IGF1R, beta-IGF1R (phosphorylated/active form) and Estrogen/Progesterone receptors. We further evaluated the IGF1R mRNA expression by quantitative RT-PCR and IGF1R mutations by direct DNA sequencing (exons 19 and 21) in 85 primary BC (42 control cases, 31 with local recurrence and 12 with distant metastasis) and in 31 local recurrences. Unconditional logistic regression analyses were performed to identify risk factors for recurrence. Results Local recurrences were associated with high-grade tumors, PR-negative and low active-IGF1R, which emerged as independent breast relapse predictors by multivariate analysis. Conclusion Patients with early BC treated with lumpectomy and radiation who have low-grade tumors and favorable markers (increased content of active IGF1R and PR-positive) have a low risk of local recurrence. Therefore, do not benefit from a boost dose on the surgical scar.

Detection of BRAF V600E mutation in colorectal cancer: comparison of automatic sequencing and real-time chemistry methodology.

Mutation V600E of BRAF, a kinase-encoding gene from the RAS/RAF/MAPK pathway, in colorectal carcinoma (CRC) suggests a sporadic origin of the disease, providing an exclusion criterion for hereditary nonpolyposis colorectal cancer. Here we describe detection of this mutation by real-time chemistry TaqMan MGB probes, confirmed by direct DNA sequencing as the gold standard. DNA was extracted from paraffin-embedded tissue from 112 tumors obtained from the EPICOLON study. Seventy-two tumors were CRC with defective DNA mismatch repair (MMR; microsatellite instability and/or loss of protein expression by immunohistochemical analysis), and 40 were proficient MMR controls. BRAF mutation was detected in 20/72 (27.8%) CRC with defective MMR and in 3/40 (7.5%) proficient MMR controls (P = 0.011). BRAF mutation was detected in 19/51 (37.3%) tumors with loss of MLH1 expression and in none of the tumors with loss of MSH2 expression (0/13). BRAF mutation was not found in cases with germline mutation of MLH1 (4/112) or MSH2 (3/112) genes. The sensitivity and specificity of our real-time chemistry were both 100% for detecting the V600E mutation. Because real-time chemistry methodology has advantages in cost, time, and labor, we consider it a valuable alternative to automatic direct sequencing, particularly for serial measurements.

Cell-free DNA concentration in pleural fluid and serum: quantitative approach and potential prognostic factor in patients with cancer and pleural effusions.

PURPOSE: The presence of pleural effusions in patients with tumors is often indicative of locally advanced or metastatic disease, and detection of malignancy in effusion samples frequently leads to a disease upstaging. Our purpose was to quantify the DNA in pleural effusion and serum in patients presenting pleural effusion in order to assess the potential prognostic impact. PATIENTS AND METHODS: The DNA level was determined by amplifying hRNase P in paired samples of serum and pleural fluid in 70 consecutive patients with cancer showing pleural effusion. A group of 30 patients without cancer was included. The correlation between serum and pleural DNA was calculated. Survival curves according to serum and pleural DNA were analyzed. RESULTS: Median DNA concentrations were greater in patients with neoplasia than in patients without malignancy: 105 ng/mL versus 40 ng/mL (P = 0.001) in serum samples, respectively; 93 ng/mL versus 21 ng/mL (P = 0.001) in pleural fluids, respectively. A positive correlation between serum and pleural levels was confirmed (r = 0.3; P < 0.05). Median survival time for patients with serum DNA < or = 105 ng/mL was 11.03 months in contrast to only 3.63 months for patients with higher values (P = 0.036). Accordingly, median survival time for patients with pleural DNA < or = 93 ng/mL was 12.3 months versus only 4.63 months in case of higher levels (P = 0.027). CONCLUSION: This study shows that there is a strong correlation between higher levels of free DNA in pleural fluid or serum and malignancy. Survival is worse for patients with higher DNA levels in serum and pleural fluid.

Gene expression signature of tolerance and lymphocyte subsets in stable renal transplants: results of a cross-sectional study.

BACKGROUND: In kidney transplants operational tolerance has been associated with up-regulation of B cell differentiation genes and an increased number of total, naive and transitional peripheral B cells. The aim is to evaluate tolerance biomarkers in different cohorts of stable renal transplants under immunosuppression. METHODS: This is a cross-sectional study conducted in renal transplants. We evaluate genetic tolerance signature and lymphocyte subsets in stable transplants treated with calcineurin inhibitors (CNI) at 1 (n=15), 5 (n=14) and 10 (n=16) years, and azathioprine-treated transplants followed 30 years (n=8). Healthy volunteers (n=10) and patients with chronic rejection (n=15) served as controls. RESULTS: We confirm that peripheral expression of IGKV1D-13 and IGKV4-1 genes by RT-PCR distinguish tolerant (n=10) from stable transplants (n=10) provided by the International Tolerance Network. Tolerance signature was defined as the lowest expression for both genes in tolerant patients. In CNI-treated patients, genetic signature of tolerance and B cells showed a time-dependent increase not observed in azathioprine-treated patients (p<0.01). Genetic tolerance signature was observed in 0% at 1, 7% at 5 and 25% at 10-years while it was not observed in azathioprine-treated and chronic rejection patients. Fifteen out of 16 CNI-treated transplants at 10 years were revaluated 3 months apart. Nine did not show the tolerance signature in any determination, 4 in one and 2 in both determinations. Genetic signature of tolerance was associated with an increase of total, naive and transitional B cells (p<0.05). CONCLUSIONS: IGKV1D-13 and IGKV4-1 gene expression and its linked B cell populations increase during follow up in CNI-treated patients. At 10 years, 2 out of 15 CNI treated patients consistently express biomarkers associated with true tolerance. In azathioprine-treated patients these biomarkers were down-regulated.

Clinical validation of a PCR assay for the detection of EGFR mutations in non-small-cell lung cancer: retrospective testing of specimens from the EURTAC trial.

The EURTAC trial demonstrated that the tyrosine kinase inhibitor (TKI) erlotinib was superior to chemotherapy as first-line therapy for advanced non-small cell lung cancers (NSCLC) that harbor EGFR activating mutations in a predominantly Caucasian population. Based on EURTAC and several Asian trials, anti-EGFR TKIs are standard of care for EGFR mutation-positive NSCLC. We sought to validate a rapid multiplex EGFR mutation assay as a companion diagnostic assay to select patients for this therapy. Samples from the EURTAC trial were prospectively screened for EGFR mutations using a combination of laboratory-developed tests (LDTs), and tested retrospectively with the cobas EGFR mutation test (EGFR PCR test). The EGFR PCR test results were compared to the original LDT results and to Sanger sequencing, using a subset of specimens from patients screened for the trial. Residual tissue was available from 487 (47%) of the 1044 patients screened for the trial. The EGFR PCR test showed high concordance with LDT results with a 96.3% overall agreement. The clinical outcome of patients who were EGFR-mutation detected by the EGFR PCR test was very similar to the entire EURTAC cohort. The concordance between the EGFR PCR test and Sanger sequencing was 90.6%. In 78.9% of the discordant samples, the EGFR PCR test result was confirmed by a sensitive deep sequencing assay. This retrospective study demonstrates the clinical utility of the EGFR PCR test in the accurate selection of patients for anti-EGFR TKI therapy. The EGFR PCR test demonstrated improved performance relative to Sanger sequencing.

Fifth Educational Symposium of the Spanish Lung Cancer Group: report on the Molecular Biology Workshop.

The majority of non-small-cell lung cancer (NSCLC) patients present with locally advanced (35%) or metastatic disease (40%); in this setting, it is of the utmost importance to balance efficacy with toxicity. However, with platinum combinations, survival has reached a "plateau", with median overall survival times of a mere 10-12 months, making it mandatory to search for new strategies and to identify more effective treatment. Molecular characteristics can be more informative than clinical features in predicting clinical benefit, and the identification of molecular markers can help define subgroups of patients who are likely to respond to different treatments, thus avoiding unnecessary toxicities and costs and providing the maximum benefit to each patient. Here we review research on biomarker assessment that was presented during the Molecular Biology Workshop held in Palma de Mallorca on 25 November 2010, during the Fifth Educational Symposium of the Spanish Lung Cancer Group.

mRNA expression of BRCA1, PIAS1, and PIAS4 and survival after second-line docetaxel in advanced gastric cancer.

Breast cancer susceptibility gene 1 (BRCA1) has a central role in chemotherapy-induced DNA damage response. The protein inhibitor of activated STAT (PIAS) family of proteins, PIAS1 and PIAS4, are also necessary for adequate DNA damage repair. To further understand the role of BRCA1 in DNA repair, we examined the mRNA expression of these genes in 133 advanced (stage III-IV) gastric cancer patients using quantitative reverse transcription polymerase chain reaction. All P values were two-sided. The median overall survival was 12.5 months (95% confidence interval [CI] = 9.8 to 13.4 months). Among 59 patients receiving second-line docetaxel, the median overall survival was 25.8 months (95% CI = 9.2 to 42.4 months) for patients with high BRCA1 expression, 19.1 months (95% CI = 3.4 to 34.8 months) for those with intermediate expression, and 9.5 months (95% CI = 8.7 to 10.2 months) for those with low expression (P = .0062). The risk of mortality was higher in patients with low BRCA1 levels compared with high BRCA1 levels (hazard ratio of death = 2.49, 95% CI = 1.03 to 5.97, P = .037). Survival in patients receiving second-line docetaxel-based chemotherapy showed a similar trend with PIAS1 and PIAS4 mRNA expression levels, although the associations for PIAS4 were not statistically significant.

Pretreatment EGFR T790M mutation and BRCA1 mRNA expression in erlotinib-treated advanced non-small-cell lung cancer patients with EGFR mutations.

PURPOSE: Advanced non-small-cell lung cancer (NSCLC) patients harboring epidermal growth factor receptor (EGFR) mutations (deletion in exon 19 or L858R) show an impressive progression-free survival of 14 months when treated with erlotinib. However, the presence of EGFR mutations can only imperfectly predict outcome. We hypothesized that progression-free survival could be influenced both by the pretreatment EGFR T790M mutation and by components of DNA repair pathways. EXPERIMENTAL DESIGN: We assessed the T790M mutation in pretreatment diagnostic specimens from 129 erlotinib-treated advanced NSCLC patients with EGFR mutations. The expression of eight genes and two proteins involved in DNA repair and four receptor tyrosine kinases was also examined. RESULTS: The EGFR T790M mutation was observed in 45 of 129 patients (35%). Progression-free survival was 12 months in patients with and 18 months in patients without the T790M mutation (P = 0.05). Progression-free survival was 27 months in patients with low BRCA1 mRNA levels, 18 months in those with intermediate levels, and 10 months in those with high levels (P = 0.02). In the multivariate analysis, the presence of the T790M mutation (HR, 4.35; P = 0.001), intermediate BRCA1 levels (HR, 8.19; P < 0.0001), and high BRCA1 levels (HR, 8.46; P < 0.0001) emerged as markers of shorter progression-free survival. CONCLUSIONS: Low BRCA1 levels neutralized the negative effect of the T790M mutation and were associated with longer progression-free survival to erlotinib. We advocate baseline assessment of the T790M mutation and BRCA1 expression to predict outcome and provide alternative individualized treatment to patients based on T790M mutations and BRCA1 expression.

Predictive biomarkers in the management of EGFR mutant lung cancer.

Activating mutations in the form of deletions in exon 19 (del 19) or the missense mutation L858R in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) predict outcome to use of EGFR tyrosine kinase inhibitors (TKIs), such as gefitinib and erlotinib. Pooled data from several phase II studies show that gefitinib and erlotinib induce responses in over 70% of NSCLC patients harboring EGFR mutations, with progression-free survival (PFS) ranging from 9 to 13 months. Two studies in Caucasian and Asian patients have confirmed that these subgroups of patients attain PFS up to 14 months. These landmark outcomes have been accompanied by new challenges, primarily the additional role of chemotherapy and the management of tumors with the secondary T790M mutation that confers resistance to EGFR TKIs. Mechanisms of resistance to reversible EGFR TKIs should be further clarified and could be related to modifications in DNA repair.

Non-small-cell lung cancer harbouring mutations in the EGFR kinase domain.

Key "driver" mutations have been discovered in specific subgroups of non-small-cell lung cancer (NSCLC) patients. Activating mutations in the form of deletions in exon 19 (del 19) or the missense mutation L858R in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR) predict outcome to EGFR tyrosine kinase inhibitors (TKIs) such as gefitinib and erlotinib. Pooled data from several phase II studies show that gefitinib and erlotinib induce responses in over 70% of NSCLC patients harbouring EGFR mutations, with progression-free survival (PFS) ranging from 9 to 13 months and median survival of around 23 months. Two studies in Caucasian and Asian patients have confirmed that these subgroups of patients attain response rates of 70% with erlotinib and ge- fitinib, including complete responses, PFS up to 14 months and median survival up to 27 months. These landmark outcomes have been accompanied by new challenges: the additional role of chemotherapy and the management of tumours with the secondary T790M mutation that confers resistance to EGFR TKIs. Mechanisms of resistance to reversible EGFR TKIs should be further clarified and could be related to modifications in DNA repair. The presence of double mutations (T790M plus either L858R or del 19) at the time of diagnosis could be much more frequent than originally thought. The sensitivity to EGFR TKIs could be greatly influenced by the expression of genes involved in the repair of DNA double-strand breaks by homologous recombination and non-homologous end joining.

The prognostic value of BRCA1 mRNA expression levels following neoadjuvant chemotherapy in breast cancer.

BACKGROUND: A fraction of sporadic breast cancers has low BRCA1 expression. BRCA1 mutation carriers are more likely to achieve a pathological complete response with DNA-damage-based chemotherapy compared to non-mutation carriers. Furthermore, sporadic ovarian cancer patients with low levels of BRCA1 mRNA have longer survival following platinum-based chemotherapy than patients with high levels of BRCA1 mRNA. METHODOLOGY/PRINCIPAL FINDINGS: Tumor biopsies were obtained from 86 breast cancer patients who were candidates for neoadjuvant chemotherapy, treated with four cycles of neoadjuvant fluorouracil, epirubicin and cyclophosphamide. Estrogen receptor (ER), progesterone receptor (PR), HER2, cytokeratin 5/6 and vimentin were examined by tissue microarray. HER2 were also assessed by chromogenic in situ hybridization, and BRCA1 mRNA was analyzed in a subset of 41 patients for whom sufficient tumor tissue was available by real-time quantitative PCR. Median time to progression was 42 months and overall survival was 55 months. In the multivariate analysis for time to progression and overall survival for 41 patients in whom BRCA1 could be assessed, low levels of BRCA1 mRNA, positive PR and negative lymph node involvement predicted a significantly lower risk of relapse, low levels of BRCA1 mRNA and positive PR were the only variables associated with significantly longer survival. CONCLUSIONS/SIGNIFICANCE: We provide evidence for a major role for BRCA1 mRNA expression as a marker of time to progression and overall survival in sporadic breast cancers treated with anthracycline-based chemotherapy. These findings can be useful for customizing chemotherapy.

Potential diagnostic value of methylation profile in pleural fluid and serum from cancer patients with pleural effusion.

BACKGROUND: The objective of this study was to investigate the diagnostic value of methylation profiles for discrimination between malignant and benign pleural effusions. A secondary objective was to examine the concordance of methylation in samples of serum and pleural fluid. METHODS: The authors used methylation-specific polymerase chain reaction (MSP) analysis to examine the promoter methylation status of 4 genes in patients with pleural effusion: death-associated protein kinase (DAPK), Ras association domain family 1A (RASSF1A), retinoic acid receptor beta (RARbeta), and p16/INK4a. Pleural effusions were collected from 87 patients who had their diagnoses confirmed on cytologic and/or histologic examinations and clinical evolution. Pleural effusions were classified as malignant (n = 53 patients) or benign (n = 34 patients). RESULTS: Methylation was detected in serum from 45.3% of patients with malignant pleural effusions and from 0% of patients with benign pleural effusions, and it was detected in pleural fluid samples from 58.5% of patients with malignant pleural effusions and from 0% of patients with benign pleural effusions (P = .001). The sensitivity of MSP was greater than that of cytologic examination alone (39.1%; P = .001). When MSP was used together with cytologic examination, sensitivity increased to 69.8% (P = .001). CONCLUSIONS: Cell-free methylated DNA in pleural fluid can be detected in patients with neoplastic malignancy in a single extraction by thoracocentesis. Adequate management of the extracted pleural fluid can provide a rapid and reliable diagnosis in patients with pleural effusions who have suspected malignancy. MSP, used together with cytologic examination, may obviate the need for other invasive diagnostic tests.

The detection of bacterial DNA in blood of rats with CCl4-induced cirrhosis with ascites represents episodes of bacterial translocation.

Bacterial DNA (bactDNA) is present in blood and ascitic fluid (AF) in a third of patients with cirrhosis and ascites, but whether this phenomenon represents episodes of bacterial translocation (BT), strictly considered when culture of mesenteric lymph nodes (MLNs) are positive, remains unknown. This study assessed the relationship between bactDNA detection in biological fluids and MLNs and went on to investigate the local and systemic inflammatory status according to its presence. Cirrhosis was induced in rats by ingestion of CCL4. A subgroup of five animals with cirrhosis received norfloxacin (5 mg/kg/day) for 7 days. MLNs and ascitic and pleural fluids were collected at laparotomy and cultured; samples were collected for identification of bactDNA and measurement of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and nitric oxide (NO). BactDNA was detected in MLNs in 12 of 19 animals (63.1%), corresponding in seven cases to culture-positive MLNs, and in five to culture-negative MLNs. BactDNA was detected in biological fluids in 11 of 19 animals (57.9%), and in all cases the same bacteria spp. detected in samples was present in MLNs. BactDNA was not detected in any biological sample from animals receiving norfloxacin. Tumor necrosis factor alpha (TNF-alpha), IL-6, and NO were similar in culture-positive and culture-negative/bactDNA-positive samples, and significantly higher than those observed in animals with culture-negative/bactDNA-negative MLNs, animals with cirrhosis that were receiving norfloxacin, and controls. In conclusion, the presence of bactDNA in biological fluids in rats with cirrhosis constitutes a marker of BT, and it is associated with a marked inflammatory response, independent of the result of the culture.

Salinibacter ruber gen. nov., sp. nov., a novel, extremely halophilic member of the Bacteria from saltern crystallizer ponds.

Five brightly red-pigmented, motile, rod-shaped, extremely halophilic bacteria were isolated from saltern crystallizer ponds in Alicante (two strains) and Mallorca (three strains), Spain. They grew optimally at salt concentrations between 20 and 30% and did not grow below 15% salts. Thus, these isolates are among the most halophilic organisms known within the domain Bacteria. The temperature optimum was 37-47 degrees C. A single, yet to be identified pigment was present, with an absorption maximum at 482 nm and a shoulder at 506-510 nm. The G+C content of the DNA was 66.3-67.7 mol% and, together, they formed a homogeneous genomic group with DNA-DNA similarities above 70%. The 16S rRNA gene sequences were almost identical to sequences recovered earlier from the saltern biomass by amplification of bacterial small-subunit rRNA genes from DNA extracted from the environment. This phylotype, earlier described as 'Candidatus Salinibacter', was shown by fluorescence in situ hybridization to contribute between 5 and 25% of the prokaryote community of the saltern crystallizers. We have therefore succeeded in isolating a bacterium from the natural environment that, although being a major component of the community, was previously known by its phylotype only. Isolation of the organism now allows formal description of a novel genus and species, for which we propose the name Salinibacter ruber gen. nov., sp. nov. The type strain is strain M31T (= DSM 13855T = CECT 5946T).