Biomarker Testing Journey Among Patients with Advanced Solid Tumors and Treatment Patterns by Homologous Recombination Repair Status: A Clinico-Genomic Database Study.

INTRODUCTION: Defects in the homologous recombination repair (HRR) pathway can include mutations in BRCA1 and BRCA2 (BRCAm) and other HRR genes (HRRm). These mutations are associated with a homologous recombination deficiency (HRD) phenotype. We evaluated testing journey and treatment patterns by BRCAm, HRRm, and HRD status in a real-world dataset. METHODS: Deidentified data for patients who had undergone comprehensive genomic profiling using FoundationOne®CDx were collected through December 31, 2020, from a real-world multi-tumor clinico-genomic database (CGDB) capturing data from clinics in the United States. Patients eligible for inclusion in this analysis had a confirmed diagnosis with advanced or metastatic disease between January 1, 2018, and December 31, 2019, for 1 of 15 solid tumor types. Objectives were to evaluate patient treatment patterns by BRCAm, HRRm, and HRD status and to describe the timing of when (throughout disease course) comprehensive genomic profiling was performed. RESULTS: Among 9457 patients included in the overall population with evaluable biomarker status, 7856 (83.1%) received ≥ 1 systemic therapy. Among the 7856 patients who received systemic therapy, 2324 (30.0%) underwent testing before first-line therapy, 4114 (52.4%) were tested after receiving first-line therapy and before receiving subsequent therapy (if any), 970 (12.3%) were tested after second-line therapy and before receiving subsequent therapy (if any), and 447 (5.7%) patients underwent testing after receiving third-line therapy. A higher proportion of patients with BRCAm, HRRm, or HRD-positive status were treated with poly(ADP-ribose) polymerase (PARP) inhibitors across all lines of therapy. There was no evidence of a meaningful difference in the proportion of patients who received other treatment (including chemotherapy and immunotherapy) by BRCAm, HRRm, or HRD status. CONCLUSION: The majority of patients from this real-world dataset underwent FoundationOne®CDx testing after initiation of first-line treatment. Testing appeared to influence treatment patterns, with a higher proportion of patients with BRCAm, HRRm, and HRD-positive disease receiving PARP inhibitors.

Real-world prevalence of homologous recombination repair mutations in advanced prostate cancer: an analysis of two clinico-genomic databases.

BACKGROUND: Homologous recombination repair mutation (HRRm) status may guide risk-stratification and treatment decisions, including polyadenosine diphosphate-ribose polymerase inhibitor use, in advanced prostate cancer. Although HRRm prevalence has been reported in single-institution studies or clinical trials, real-world HRRm prevalence in diverse populations is unknown. We describe HRRm in the clinical setting using two real-world clinicogenomic databases: the Flatiron Health and Foundation Medicine, Inc. Clinico-Genomic Database (CGDB), a national electronic health record-derived database, and the American Association for Cancer Research Project Genomics Evidence Neoplasia Information Exchange (GENIE). METHODS: This cross-sectional analysis included 3757 individuals diagnosed with prostate cancer who had next generation sequencing (NGS) as standard of care. The CGDB included men with advanced/metastatic prostate cancer and genetic data included both germline and somatic pathogenic mutations. The GENIE analysis included men with prostate cancer whose received NGS as standard of care, but the data were filtered to include somatic mutations only. Due to key differences among databases, direct comparisons were not possible. Overall prevalence of HRRm was calculated and stratified by demographic and clinical characteristics. RESULTS: HRRm prevalence (combined germline and somatic) in CGDB (n = 487) was 24.6% (95% CI 20.9-28.7%), with no major differences across demographic and disease characteristic subgroups. HRRm prevalence (somatic) in GENIE (n = 3270) was 11.0% (95% CI 10.0-12.1%), which varied between 9.5% and 18.4% across treatment centers. CONCLUSIONS: Approximately one-quarter of patients with advanced/metastatic prostate cancer in the CGDB had germline and/or somatic HRRm, which is consistent with clinical trials such as the PROfound study that used a similar NGS platform and algorithm to define HRRm. In the GENIE database, HRRm prevalence varied by treatment center or NGS platform. More research is needed to understand real-world HRRm prevalence variations.

Association Between Homologous Recombination Repair Biomarkers and Survival in Patients With Solid Tumors.

PURPOSE: Mutations in BRCA1 and/or BRCA2 (BRCAm), other homologous recombination repair genes (HRRm), and homologous recombination deficiency (HRD) lead to an accumulation of genomic alterations that can drive tumorigenesis. The prognostic impact of these HRR pathway defects on overall survival (OS) in patients not receiving poly (ADP-ribose) polymerase inhibitors (PARPi) or immunotherapy is unclear. We evaluated the association of HRR biomarkers with OS in patients with advanced solid tumors receiving therapy excluding PARPi and immunotherapy. METHODS: Deidentified data were collected through December 31, 2020, from a real-world clinicogenomic database (CGDB) with data originating from approximately 280 cancer clinics in the United States. Patients age 18 years and older with an advanced/metastatic diagnosis between 2018 and 2019 for 1 of 15 solid tumors and available data in the CGDB were included. The primary analysis evaluated the association between HRR pathway biomarkers and OS, using start of second-line therapy as the index date (to reduce immortal time bias). RESULTS: A total of 9,457 patients had available data for BRCA/HRR and 5,792 for HRD status; 4,890 (51.7%) were women and mean (SD) age was 65.9 (11.5) years. For the primary analysis, adjusted hazard ratios for OS were BRCAm (n = 156) versus BRCA wild-type (wt; n = 3,131; 0.83 [95% CI, 0.60 to 1.17]); for HRRm (n = 467) versus HRRwt (n = 282; 0.95 [95% CI, 0.79 to 1.14]); and for HRD-positive (n = 447) versus -negative (n = 1,687; 1.22 [95% CI, 1.02 to 1.47]). Results were similar using start of first-line and start of third-line therapy as index dates. CONCLUSION: This large, real-world study found no association between OS and either BRCA or HRR status but identified a possible linkage between HRD positivity and shorter median OS in patients with advanced solid tumors who did not receive PARPi or immunotherapy.

Evaluation and Comparison of Real-World Databases for Conducting Research in Patients With Colorectal Cancer.

PURPOSE: Evaluating whether patient populations in clinico-genomic oncology databases are comparable with whom in other databases without genomic component is important. METHODS: Four databases were compared for colorectal cancer (CRC) cases and stage IV CRC cases: American Association for Cancer Research Project Genomics Evidence Neoplasia Information Exchange Biopharma Collaborative (GENIE-BPC), The Cancer Genome Atlas (TCGA), SEER-Medicare, and MarketScan Commercial and Medicare Supplemental claims databases. These databases were also compared with the SEER registry database which serves as national benchmarks. Demographics, clinical characteristics, and overall survival were compared in patients with newly diagnosed CRC and patients with stage IV CRC across databases. Treatment patterns were further compared in patients with stage IV CRC. RESULTS: A total of 65,976 patients with CRC and 13,985 patients with stage IV CRC were identified. GENIE-BPC had the youngest patient population (mean age [years]: CRC, 54.1; stage IV CRC, 52.7). SEER-Medicare had the oldest patient population (CRC, 77.7; stage IV CRC, 77.3). Most patients were male and of White race across databases. GENIE-BPC had the highest proportion of patients with stage IV CRC (48.4% v other databases 13.8%-25.4%) and patients receiving treatments (95.7% v 37.6%-59.1%). Infusional fluorouracil, leucovorin, and oxaliplatin with or without bevacizumab was the most common regimen across databases accounting for 47.3%-78.5% of patients receiving first line of therapy. The median survival from diagnosis was 36, 94, 44 months (CRC) and 23, 36, 15 months (stage IV CRC) for patients in GENIE-BPC after left truncation, TCGA, and SEER-Medicare databases, respectively. CONCLUSION: Compared with other databases, GENIE-BPC had the youngest patients with CRC with the most advanced disease and the largest proportion of patients receiving treatment. Investigators should consider adjustments when extrapolating results from clinico-genomic databases to the general CRC population.

A comprehensive literature review and meta-analysis of the prevalence of pan-cancer BRCA mutations, homologous recombination repair gene mutations, and homologous recombination deficiencies.

There is significant improvement in the outcomes following treatment with PARP inhibitors among patients with certain tumors that have BRCA mutations (BRCAm), homologous recombination repair (HRR) gene mutations, or homologous recombination deficiency (HRD) positivity. We performed a literature review and meta-analysis to evaluate the prevalence of BRCA1/2m, HRR gene mutations, and HRD positivity across multiple cancers. There were 265 publications on BRCA1/2 mutation prevalence, 189 on HRR gene mutation prevalence, and 7 on HRD positivity prevalence. The prevalences of germline BRCA1m and BRCA2m were 7.8% and 5.7% for breast cancer, 13.5% and 6.6% for ovarian cancer, 0.5% and 3.5% for prostate cancer, and 1.1% and 4.1% for pancreatic cancer, respectively. The prevalences of somatic BRCA1m and BRCA2m were 3.4% and 2.7% for breast cancer, 4.7% and 2.9% for ovarian cancer, 5.7% and 3.2% for prostate cancer, and 1.2% and 2.9% for pancreatic cancer, respectively. We identified 189 studies with over 418,649 samples across 25 tumor types that examined mutations in one or more HRR genes other than BRCA1/2. The prevalence of mutations among HRR genes remained low (less than 1%), with ATM (5.2%), CHEK2 (1.6%), and PALB2 (0.9%) exhibiting the highest prevalence. Seven studies evaluated HRD positivity in breast, ovarian, and prostate cancer patients. The prevalence of HRD positivity was 56% overall (95% CI = 48%-64%). The understanding of biomarker prevalence across tumor types and standardization of biomarker assays could have important clinical implications.

A Systematic Review and Meta-Analysis on the Prognostic Value of BRCA Mutations, Homologous Recombination Gene Mutations, and Homologous Recombination Deficiencies in Cancer.

Patients with BRCA1/2 mutations (BRCAm), loss-of-function mutations in other homologous recombination repair (HRRm) genes, or tumors that are homologous recombination deficiency positivity (HRD+) demonstrate a robust response to PARPi therapy. We conducted a systematic literature review and meta-analysis to evaluate the prognostic value of BRCAm, HRRm, and HRD+ on overall survival (OS) among those treated by chemotherapy or targeted therapy other than PARPi across tumor types. A total of 135 eligible studies were included. Breast cancer (BC) patients with BRCA1/2m had a similar overall survival (OS) to those with wild-type BRCA1/2 (BRCA1/2 wt) across 18 studies. Ovarian cancer (OC) patients with BRCA1/2m had a significantly longer OS than those with BRCA1/2 wt across 24 studies reporting BRCA1m and BRCA2m, with an HR of 0.7 (0.6-0.8). Less OS data were reported for other tumors: 6 studies for BRCA2m compared with BRCA2 wt in prostate cancer with an HR of 1.9 (1.1-3.2) and 2 studies for BRCA1/2m compared with BRCA1/2 wt in pancreatic cancer with an HR of 1.5 (0.8-3.1). Only 4 studies reported HRD+ by either BRCA m or genomic instability score (GIS) ≥ 42 and OS by HRD status. The HR was 0.67 (0.43-1.02) for OS with HRD+ vs. HRD-. A total of 15 studies reported the association between HRRm and OS of cancers in which one or more HRR genes were examined. The HR was 1.0 (0.7-1.4) comparing patients with HRRm to those with HRR wild-type across tumors. Our findings are useful in improving the precision and efficacy of treatment selection in clinical oncology.

Association of clinico-genomic characteristics with tumor mutational burden in small cell lung cancer patients.

Aim: We evaluated the relationship between clinical and genomic characteristics and tumor mutational burden (TMB) in small cell lung cancer. Materials & methods: In a retrospective analysis of small cell lung cancer patients aged ≥18, we assessed treatment patterns and survival in relation to TMB; the association of clinical and genomic characteristics with TMB was determined by multivariate regression. High TMB (TMB-H) was defined as ≥10 mutations/megabase. Results: Among 186 patients, treatment patterns and overall survival were similar for TMB-H and non-TMB-H patients. TMB was determined for 179 patients, 41.9% of whom were TMB-H. Short variants of LRP1B, FAT3, MLL3, MED12 and NOTCH3 were significantly associated with TMB-H (p ≤ 0.01). Conclusion: Neither treatment patterns nor survival differed by TMB status.

Prevalence of High Tumor Mutational Burden and Association With Survival in Patients With Less Common Solid Tumors.

Importance: Tumor mutational burden (TMB) is a potential biomarker associated with response to immune checkpoint inhibitor therapies. The prognostic value associated with TMB in the absence of immunotherapy is uncertain. Objective: To assess the prevalence of high TMB (TMB-H) and its association with overall survival (OS) among patients not treated with immunotherapy with the same 10 tumor types from the KEYNOTE-158 study. Design, Setting, and Participants: This retrospective cohort study evaluated the prognostic value of TMB-H, assessed by Foundation Medicine (FMI) and defined as at least 10 mutations/megabase (mut/Mb) in the absence of immunotherapy. Data were sourced from the deidentified Flatiron Health-FMI clinicogenomic database collected up to July 31, 2018. Eligible patients were aged 18 years or older with any of the following solid cancer types: anal, biliary, endometrial, cervical, vulvar, small cell lung, thyroid, salivary gland, mesothelioma, or neuroendocrine tumor. Patients with microsatellite instability-high tumors were excluded from primary analysis. For OS analysis, patients were excluded if immunotherapy started on the FMI report date or earlier or if patients died before January 1, 2012, and patients were censored if immunotherapy was started later than the FMI report date. Data were analyzed from November 2018 to February 2019. Main Outcomes and Measures: Overall survival was analyzed using the Kaplan-Meier method and Cox proportional hazards model, adjusting for age, sex, cancer types, practice type, and albumin level. Results: Of 2589 eligible patients, 1671 (64.5%) were women, and the mean (SD) age was 63.7 (11.7) years. Median (interquartile range) TMB was 2.6 (1.7-6.1) mut/Mb, and 332 patients (12.8%) had TMB-H (≥10 mut/Mb). Prevalence of TMB-H was highest among patients with small cell lung cancer (40.0%; 95% CI, 34.7%-45.6%) and neuroendocrine tumor (29.3%; 95% CI, 22.8%-36.6%) and lowest was among patients with mesothelioma (1.2%; 95% CI, 0.3%-4.4%) and thyroid cancer (2.7%; 95% CI, 1.2%-5.7%). Adjusted hazard ratio for OS of patients not treated with immunotherapy with TMB-H vs those without TMB-H was 0.94 (95% CI, 0.77-1.13). Comparable results were observed when including patients with high microsatellite instability tumors and calculating OS from first observed antineoplastic treatment date. Conclusions and Relevance: These findings suggest that prevalence of TMB-H varies widely depending on tumor type and TMB-H does not appear to be a factor associated with OS among patients across these cancer types treated in the absence of immunotherapy.

Chemotherapy treatments, costs of care, and survival for elderly patients diagnosed with cervical cancer: an observational study.

Objective: To describe chemotherapy treatments, associated health care use and costs, and survival for women diagnosed with cervical cancer in the United States.Methods: This was a retrospective cohort study of patients aged ≥65 years, identified in linked Surveillance, Epidemiology, and End Results (SEER) and Medicare databases. Women with a new primary diagnosis of cervical cancer between January 2007 and December 2013 were followed until December 2014. Systemic chemotherapy treatments, health care visits and costs (2016 USD rates), and survival were determined by the line of therapy.Results: Of 1651 women in the analysis, 810 (49.1%) were diagnosed at stages I or II, 411 (24.9%) at stage III, and 430 (26.0%) at stage IV. A total of 225 (13.6%) women received first-line (1L) systemic chemotherapy. Of those who received 1L chemotherapy, 73 (32.4%) received second-line (2L) chemotherapy, and 29 (12.9%) received third-line (3L) chemotherapy. During 1L and 2L chemotherapies, patients averaged 5.9 and 6.5 health care visits per month, respectively, and incurred total mean health care costs per patient per month of $7098 and $8770, respectively. Median survival from the start of 1L and 2L chemotherapy was 14.0 and 10.4 months, respectively.Conclusion: Elderly patients with advanced cervical cancer had a poor prognosis, with a median survival of 14 months or less, and had no standard of care for 2L therapy. Systemic chemotherapies pose a substantial economic burden in the range of $7000 to $9000 per patient per month. These results highlight the high unmet medical need among elderly patients with cervical cancer.

Survival, Chemotherapy Treatments, and Health Care Utilization Among Patients with Advanced Small Cell Lung Cancer: An Observational Study.

INTRODUCTION: Most cases of small cell lung cancer (SCLC) are diagnosed at an advanced stage. The objective of this study was to investigate patient characteristics, survival, chemotherapy treatments, and health care use after a diagnosis of advanced SCLC in subjects enrolled in a health system network. METHODS: This was a retrospective cohort study of patients aged ≥ 18 years who either were diagnosed with stage III/IV SCLC or who progressed to advanced SCLC during the study period (2005-2015). Patients identified from the Indiana State Cancer Registry and the Indiana Network for Patient Care were followed from their advanced diagnosis index date until the earliest date of the last visit, death, or the end of the study period. Patient characteristics, survival, chemotherapy regimens, associated health care visits, and durations of treatment were reported. Time-to-event analyses were performed using the Kaplan-Meier method. RESULTS: A total of 498 patients with advanced SCLC were identified, of whom 429 were newly diagnosed with advanced disease and 69 progressed to advanced disease during the study period. Median survival from the index diagnosis date was 13.2 months. First-line (1L) chemotherapy was received by 464 (93.2%) patients, most commonly carboplatin/etoposide, received by 213 (45.9%) patients, followed by cisplatin/etoposide (20.7%). Ninety-five (20.5%) patients progressed to second-line (2L) chemotherapy, where topotecan monotherapy (20.0%) was the most common regimen, followed by carboplatin/etoposide (14.7%). Median survival was 10.1 months from 1L initiation and 7.7 months from 2L initiation. CONCLUSION: Patients in a regional health system network diagnosed with advanced SCLC were treated with chemotherapy regimens similar to those in earlier reports based on SEER-Medicare data. Survival of patients with advanced SCLC was poor, illustrating the lack of progress over several decades in the treatment of this lethal disease and highlighting the need for improved treatments.

Chemotherapy treatments, costs of care, and survival for patients diagnosed with small cell lung cancer: A SEER-Medicare study.

OBJECTIVES: The effectiveness and costs of new treatments should be assessed in relation to existing practice. We describe treatments, survival and costs for advanced or metastatic small cell lung cancer (SCLC) patients receiving systemic therapy in the period preceding the introduction of immunotherapies. MATERIALS AND METHODS: This was a retrospective cohort study of patients aged ≥65 years, identified using linked Surveillance, Epidemiology, and End Results and Medicare databases. Individuals with a new primary diagnosis of SCLC between January 2007 and December 2013 were followed until December 2014. Chemotherapy treatments, health care visits and costs (in 2016 USD), and survival were determined by line of therapy. RESULTS: A total of 11 812 patients were identified with SCLC. First-line (1L) chemotherapy was received by 6509 (55.1%) patients, most (93.2%) with carboplatin- (71.0%) or cisplatin- (22.2%) based therapies, typically combined with etoposide (79.2%). Second- (2L) and third- (3L) line chemotherapies were received by 2238 (18.9%) and 679 (5.7%) patients, of which 48.4% and 30.9%, respectively, were platinum-based. The median durations of 1L, 2L, and 3L carboplatin-based therapies were 5.9, 4.8, and 5.4 months, respectively, and the corresponding durations of cisplatin-based therapies were 5.3, 4.2, and 5.3 months. During 1L, 2L, and 3L chemotherapies, patients averaged 8.2, 7.4, and 7.3 health care visits per month, respectively, and incurred total mean health care costs of $60 223, $42 636, and $35 903 per patient, respectively. Median survival from the start of 1L, 2L, and 3L chemotherapy was 9.2, 6.0, and 5.7 months, respectively. CONCLUSION: First-line chemotherapy was primarily platinum-based, and a plethora of different regimens was used for 2L and 3L chemotherapies. Median survival from the start of 1L chemotherapy was 9 months, with an associated health care cost of $60 000. These data highlight an unmet medical need among SCLC patients receiving systemic therapy.

Treatment patterns, health care resource utilization, and costs in patients with relapsed/refractory Hodgkin lymphoma treated with brentuximab vedotin.

Data are limited on the real-world utilization and costs of brentuximab vedotin (BV) among patients with relapsed/refractory Hodgkin lymphoma (rrHL) in the United States. A total of 219 BV patients identified from the Truven MarketScan® databases were followed up for a median of 2.9 years before and 1.0 year after initiation of BV. Of these patients, 109 (50.6%) received systemic therapy after BV (post-BV ST). Median duration of treatment was short for BV (2.1 months) and post-BV ST treatment (1.3 months); time to next treatment was 6.2 and 9.1 months, respectively. Average total US dollar 2014 costs/person for BV and post-BV ST line of therapy were $167,152 and $132,115, respectively; mean per-patient-per-month costs for BV and post-BV ST were $30,434 and $29,138, respectively. Findings underscore the unmet medical need and substantial economic burden in BV-treated patients with rrHL.

A quantitative and efficient approach to select MIRU-VNTR loci based on accumulation of the percentage differences of strains for discriminating divergent Mycobacterium tuberculosis sublineages.

Although several optimal mycobacterial interspersed repetitive units-variable number tandem repeat (MIRU-VNTR) loci have been suggested for genotyping homogenous Mycobacterium tuberculosis, including the Beijing genotype, a more efficient and convenient selection strategy for identifying optimal VNTR loci is needed. Here 281 M. tuberculosis isolates were analyzed. Beijing genotype and non-Beijing genotypes were identified, as well as Beijing sublineages, according to single nucleotide polymorphisms. A total of 22 MIRU-VNTR loci were used for genotyping. To efficiently select optimal MIRU-VNTR loci, we established accumulations of percentage differences (APDs) between the strains among the different genotypes. In addition, we constructed a minimum spanning tree for clustering analysis of the VNTR profiles. Our findings showed that eight MIRU-VNTR loci displayed disparities in h values of ≥0.2 between the Beijing genotype and non-Beijing genotype isolates. To efficiently discriminate Beijing and non-Beijing genotypes, an optimal VNTR set was established by adding loci with APDs ranging from 87.2% to 58.8%, resulting in the construction of a nine-locus set. We also found that QUB11a is a powerful locus for separating ST10s (including ST10, STF and STCH1) and ST22s (including ST22 and ST8) strains, whereas a combination of QUB11a, QUB4156, QUB18, Mtub21 and QUB26 could efficiently discriminate Beijing sublineages. Our findings suggested that two nine-locus sets were not only efficient for distinguishing the Beijing genotype from non-Beijing genotype strains, but were also suitable for sublineage genotyping with different discriminatory powers. These results indicate that APD represents a quantitative and efficient approach for selecting MIRU-VNTR loci to discriminate between divergent M. tuberculosis sublineages.

Persistently high prevalence of primary resistance and multidrug resistance of tuberculosis in Heilongjiang Province, China.

BACKGROUND: The spread of multidrug-resistant tuberculosis (MDR-TB) Mycobacterium tuberculosis (M. tuberculosis) strains has been a big challenge to the TB control and prevention in China. Knowledge about patterns of drug resistance in TB high-burden areas of China is crucial to develop appropriate control strategies. We conducted a comprehensive investigation of the resistance pattern of M. tuberculosis in Heilongjiang Province. METHODS: 1427 M. tuberculosis clinical strains were isolated from pulmonary TB patients hospitalized between 2007 and 2012. The susceptibility of the isolates to the first-line anti-TB drugs and the resistance of MDR M. tuberculosis to fluoroquinolones were examined. We also performed a statistical analysis to identify the correlated risk factors for high burden of MDR-TB. RESULTS: The global resistance rates of 2007-2012 to the first-line drugs and MDR were 57.0 and 22.8 %, respectively. Notably, the primary MDR-TB and pan-resistance rates were as high as 13.6 and 5.0 %, respectively. Of MDR M. tuberculosis isolates (2009), approximately 13 % were not susceptible to any of the fluoroquinolones tested. Being age of 35 to 54, high re-treatment proportion, the presence of cavity lesion, and high proportion of shorter hospitalization are correlated with the development of MDR-TB. CONCLUSIONS: The high prevalence of drug resistant, MDR-TB, and fluoroquinolone-resistant MDR-TB is a big concern for TB control. More importantly, in order to control the development of MDR-TB effectively, we need to pay more attention to the primary resistance. Targeting reducing the prevalence of the risk factors may lead to better TB control in China.

Genetic heterogeneity of pseudoxanthoma elasticum: the Chinese signature profile of ABCC6 and ENPP1 mutations.

Pseudoxanthoma elasticum (PXE), an autosomal recessive disorder characterized by ectopic mineralization, is caused by mutations in the ABCC6 gene. We examined clinically 29 Chinese PXE patients from unrelated families, so far the largest cohort of Asian PXE patients. In a subset of 22 patients, we sequenced ABCC6 and another candidate gene, ENPP1, and conducted pathogenicity analyses for each variant. We identified a total of 17 distinct mutations in ABCC6, 15 of them being, to our knowledge, previously unreported, including 5 frameshift and 10 missense variants. In addition, a missense mutation in combination with a recurrent nonsense mutation in ENPP1 was discovered in a pediatric PXE case. No cases with p.R1141X or del23-29 mutations, common in Caucasian patient populations, were identified. The 10 missense mutations in ABCC6 were expressed in the mouse liver via hydrodynamic tail-vein injections. One mutant protein showed cytoplasmic accumulation indicating abnormal subcellular trafficking, while the other nine mutants showed correct plasma membrane location. These nine mutations were further investigated for their pathogenicity using a recently developed zebrafish mRNA rescue assay. Minimal rescue of the morpholino-induced phenotype was achieved with eight of the nine mutant human ABCC6 mRNAs tested, implying pathogenicity. This study demonstrates that the Chinese PXE population harbors unique ABCC6 mutations. These genetic data have implications for allele-specific therapy currently being developed for PXE.

Premature termination codon read-through in the ABCC6 gene: potential treatment for pseudoxanthoma elasticum.

Pseudoxanthoma elasticum (PXE) is an autosomal recessive disorder manifesting with ectopic connective tissue mineralization, caused by mutations in the ABCC6 gene, with ~35% of all mutations being premature termination mutations. In this study, we investigated the therapeutic potential of the nonsense codon read-through-inducing drug, PTC124, in treating PXE. The ability of this drug to facilitate read-through of nonsense mutations was examined in HEK293 cells transfected with human ABCC6 expression constructs harboring seven different PXE-associated nonsense mutations, and was evaluated by immunofluorescence and In-Cell ELISA. Our data demonstrated that PTC124 did not exhibit cytotoxicity in concentrations up to 20 µg ml(-1), and the facilitated read-through varied not only with dose but also with sequence context. Considering the redundancy of the genetic code, it was postulated that in case of the most common recurrent nonsense mutation, p.R1141X, the read-through may result in substitution of the arginine 1,141 by glycine, tryptophan, or cysteine. Their potential pathogenicity was tested in a recently developed zebrafish messenger RNA (mRNA) rescue assay, and demonstrated that all three mRNA transcripts were able to rescue abcc6a morpholino-induced phenotype of zebrafish. Thus, our results suggest that read-through of nonsense mutations in ABCC6 by PTC124 may have potential for pharmacologic treatment of PXE.

Type I signal peptidase and protein secretion in Staphylococcus aureus.

Staphylococcus aureus is an important human pathogen whose virulence relies on the secretion of many different proteins. In general, the secretion of most proteins in S. aureus, as well as other bacteria, is dependent on the type I signal peptidase (SPase)-mediated cleavage of the N-terminal signal peptide that targets a protein to the general secretory pathway. The arylomycins are a class of natural product antibiotics that inhibit SPase, suggesting that they may be useful chemical biology tools for characterizing the secretome. While wild-type S. aureus (NCTC 8325) is naturally resistant to the arylomycins, sensitivity is conferred via a point mutation in its SPase. Here, we use a synthetic arylomycin along with a sensitized strain of S. aureus and multidimensional protein identification technology (MudPIT) mass spectrometry to identify 46 proteins whose extracellular accumulation requires SPase activity. Forty-four possess identifiable Sec-type signal peptides and thus are likely canonically secreted proteins, while four also appear to possess cell wall retention signals. We also identified the soluble C-terminal domains of two transmembrane proteins, lipoteichoic acid synthase, LtaS, and O-acyteltransferase, OatA, both of which appear to have noncanonical, internal SPase cleavage sites. Lastly, we identified three proteins, HtrA, PrsA, and SAOUHSC_01761, whose secretion is induced by arylomycin treatment. In addition to elucidating fundamental aspects of the physiology and pathology of S. aureus, the data suggest that an arylomycin-based therapeutic would reduce virulence while simultaneously eradicating an infection.

Chemotherapeutic sensitization of leptomycin B resistant lung cancer cells by pretreatment with doxorubicin.

The development of novel targeted therapies has become an important research focus for lung cancer treatment. Our previous study has shown leptomycin B (LMB) significantly inhibited proliferation of lung cancer cells; however, p53 wild type lung cancer cells were resistant to LMB. Therefore, the objective of this study was to develop and evaluate a novel therapeutic strategy to sensitize LMB-resistant lung cancer cells by combining LMB and doxorubicin (DOX). Among the different treatment regimens, pretreatment with DOX (pre-DOX) and subsequent treatment with LMB to A549 cells significantly decreased the 50% inhibitory concentration (IC50) as compared to that of LMB alone (4.4 nM vs. 10.6 nM, P<0.05). Analysis of cell cycle and apoptosis by flow cytometry further confirmed the cytotoxic data. To investigate molecular mechanisms for this drug combination effects, p53 pathways were analyzed by Western blot, and nuclear proteome was evaluated by two dimensional-difference gel electrophoresis (2D-DIGE) and mass spectrometry. In comparison with control groups, the levels of p53, phospho-p53 (ser15), and p21 proteins were significantly increased while phospho-p53 (Thr55) and survivin were significantly decreased after treatments of pre-DOX and LMB (P<0.05). The 2D-DIGE/MS analysis identified that sequestosome 1 (SQSTM1/p62) had a significant increase in pre-DOX and LMB-treated cells (P<0.05). In conclusion, our results suggest that drug-resistant lung cancer cells with p53 wild type could be sensitized to cell death by scheduled combination treatment of DOX and LMB through activating and restoring p53 as well as potentially other signaling pathway(s) involving sequestosome 1.

CRM1-dependent p53 nuclear accumulation in lung lesions of a bitransgenic mouse lung tumor model.

The p53 tumor suppressor gene plays an essential role in tumorigenesis, and the chromosomal region maintenance 1 (CRM1) has been suggested to export p53 protein from the nucleus to the cytoplasm. The objectives of the present study were to evaluate p53 expression and subcellular localization as well as CRM1 expression using immunohistochemistry in our established bitransgenic mouse lung tumor model. In this model, expression of the mutant human Ki-rasG12C allele was regulated in a doxycycline (DOX)-inducible, lung-specific manner. Following treatment with curcumin, we found that although overall p53 expression levels were not significantly changed among the three groups, lung lesions in mice treated with DOX alone had the highest proportion of N>C (nucleus predominant) p53 staining (46±7%), followed by lung lesions in mice co-treated with DOX and curcumin (31±12%) and controls (17±4%). CRM1 expression was dramatically inhibited in lung lesions in mice treated with DOX (0±0) as compared to controls (90±17, P=0.001), and could be partially reversed after curcumin treatment (47±21, P=0.028, DOX vs. DOX+curcumin). Collectively, the results from this study demonstrated that p53 accumulated in the nucleus in lung lesions in mice expressing the mutant Ki-rasG12C transgene as a result of down-regulation of CRM1. Furthermore, these alterations could be partially reversed by curcumin treatment. p53 subcellular localization resulting from CRM1 alterations may play an important role in lung tumorigenesis.