Adapting to Change: A Thoracic Oncology Team's Perspective.

With targeted therapies, outcomes for patients with NSCLC are improving, but better monitoring for AEs is needed.

Involvement of budding yeast Rad5 in translesion DNA synthesis through physical interaction with Rev1.

DNA damage tolerance (DDT) is responsible for genomic stability and cell viability by bypassing the replication block. In Saccharomyces cerevisiae DDT employs two parallel branch pathways to bypass the DNA lesion, namely translesion DNA synthesis (TLS) and error-free lesion bypass, which are mediated by sequential modifications of PCNA. Rad5 has been placed in the error-free branch of DDT because it contains an E3 ligase domain required for PCNA polyubiquitination. Rad5 is a multi-functional protein and may also play a role in TLS, since it interacts with the TLS polymerase Rev1. In this study we mapped the Rev1-interaction domain in Rad5 to the amino acid resolution and demonstrated that Rad5 is indeed involved in TLS possibly through recruitment of Rev1. Genetic analyses show that the dual functions of Rad5 can be separated and reconstituted. Crystal structure analysis of the Rad5-Rev1 interaction reveals a consensus RFF motif in the Rad5 N-terminus that binds to a hydrophobic pocket within the C-terminal domain of Rev1 that is highly conserved in eukaryotes. This study indicates that Rad5 plays a critical role in pathway choice between TLS and error-free DDT.

Error-free DNA-damage tolerance in Saccharomyces cerevisiae.

DNA-damage tolerance (DDT) is an important mechanism for living cells to bypass replication blocks on the template strand. In Saccharomyces cerevisiae, DDT is mediated by the RAD6 epistasis group of genes, consisting of two parallel pathways: error-prone translesion DNA synthesis (TLS), and error-free lesion bypass. The two pathways are activated by sequential ubiquitination of PCNA on the Lys164 residue. When a replication fork is stalled at a lesion, PCNA is first monoubiquitinated by Rad6-Rad18, which leads to the TLS pathway. The subsequent ubiquitination by the Mms2-Ubc13-Rad5 complex on the monoubiquitinated PCNA is to form a Lys63-linked polyubiquitin chain that promotes error-free lesion bypass. While the TLS pathway has been extensively characterized, the molecular events leading to error-free lesion bypass by polyubiquitinated PCNA are largely obscure. Furthermore, PCNA can also be sumoylated at the same Lys164 residue, which helps to recruit Srs2, a helicase and anti-recombinase. This review summarizes recent advances in our understanding of error-free DDT and its interplay with Srs2 and homologous recombination.

Spontaneous mutagenesis assay.

Spontaneous mutations occur in the DNA as a result of endogenous cellular processes. The antimutagenic processes within a cell consist primarily of mechanisms of DNA repair, which are critical for maintenance of genomic stability, while mutagenic processes include mistakes by the replicative machinery and spontaneous alterations in the base chemistry of DNA. In Saccharomyces cerevisiae spontaneous mutagenesis assays are typically employed when studying the DNA damage repair pathways, since loss of one of these mechanisms results in a detectable increase in the spontaneous mutation rate, which is determined by first growing cells to log phase, then subculturing them to a very low concentration and incubating for several days. This allows for many cell divisions and thus many opportunities for mutations to occur in the genome. The selection of mutants is typically based on a specific genetic marker such as an auxotrophic marker, and the total number is compared to the total number of viable cells in order to determine the mutation rate for an exponentially growing culture.

The Rad5 helicase activity is dispensable for error-free DNA post-replication repair.

DNA post-replication repair (PRR) functions to bypass replication-blocking lesions and is subdivided into two parallel pathways: error-prone translesion DNA synthesis and error-free PRR. While both pathways are dependent on the ubiquitination of PCNA, error-free PRR utilizes noncanonical K63-linked polyubiquitinated PCNA to signal lesion bypass through template switch, a process thought to be dependent on Mms2-Ubc13 and a RING finger motif of the Rad5 ubiquitin ligase. Previous in vitro studies demonstrated the ability of Rad5 to promote replication fork regression, a function dependent on its helicase activity. To investigate the genetic and mechanistic relationship between fork regression in vitro and template switch in vivo, we created and characterized site-specific mutations defective in the Rad5 RING or helicase activity. Our results indicate that both the Rad5 ubiquitin ligase and the helicase activities are exclusively involved in the same error-free PRR pathway. Surprisingly, the Rad5 helicase mutation abolishes its physical interaction with Ubc13 and the K63-linked PCNA polyubiquitin chain assembly. Indeed, physical fusions of Rad5 with Ubc13 bypass the requirement for either the helicase or the RING finger domain. Since the helicase domain overlaps with the SWI/SNF chromatin-remodelling domain, our findings suggest a structural role of this domain and that the Rad5 helicase activity is dispensable for error-free lesion bypass.

Implementing and sustaining school-located influenza vaccination programs: perspectives from five diverse school districts.

Local health departments have typically led school-located influenza vaccination (SLIV) programs, assuming resource-intensive roles in design, coordination, and vaccination. This level of involvement is often not financially sustainable over time. Five diverse school districts in Los Angeles County designed, implemented, refined, and institutionalized their own SLIV programs over 3 years by identifying and maximizing their existing resources. School district nurses and other staff served as project leaders, designing their own vaccination administration process, parental consent, and clinic promotional models. Two districts expanded their existing school immunization clinics and three developed their vaccination capacity with community partnerships. Each district tailored its program in creative resource-minimum ways, sometimes abandoning or adopting new methods/technologies based on the effectiveness in previous seasons. The shared experiences and strategies between district nurses and the local health department described in this article illustrate a district's ability to develop a tailor-made SLIV program, often in less than ideal conditions.

A phase II trial of carboplatin/vinorelbine with pegfilgrastim support for the treatment of patients with advanced non-small cell lung cancer.

INTRODUCTION: The impact of chemotherapy dose delivery has not been well studied in patients with non-small cell lung cancer (NSCLC). Overlapping hematologic toxicities commonly limit planned dose intensity of combination chemotherapy regimens. A phase II study investigating carboplatin and vinorelbine, supported by pegfilgrastim, in the treatment of patients with advanced NSCLC was performed. METHODS: Chemotherapy-naïve patients with locally advanced or metastatic NSCLC were treated with carboplatin area under the curve (AUC) 6 mg/ml per minute intravenously on day 1 and vinorelbine 30 mg/m2 intravenously on days 1 and 8 every 3 weeks for four planned cycles. Pegfilgrastim was administered on day 9 of each cycle as a 6-mg subcutaneous injection. The primary endpoint was incidence of cycle 1 febrile neutropenia. Secondary endpoints included incidence of grade 3/4 hematologic and nonhematologic toxicities, delivered dose intensity, and overall survival. RESULTS: Thirty patients (21 men, 9 women) with a median age of 61 years (range, 43-79) were enrolled. Of 120 planned patient cycles, 101 (84%) were completed. There was one episode of cycle 1 febrile neutropenia. Overall response rate was 27%. Median dose delivered for vinorelbine was 17.2 mg/m2 per week, representing a delivered dose intensity of 86%. Median survival was 9.4 months (95% confidence interval: 6.1-18.0) with a 3-year survival rate of 20%. CONCLUSIONS: This regimen of carboplatin and vinorelbine with pegfilgrastim support was associated with a low rate of febrile neutropenia and good maintenance of planned dose intensity. Although response and survival are similar to other chemotherapy regimens in advanced NSCLC, studies optimizing chemotherapy delivery in this setting may help inform treatment approaches in patients with earlier stage disease.

A phase I study of dose-dense topotecan given upfront to standard therapy in patients with small cell lung cancer.

OBJECTIVE: To determine the feasibility and maximum tolerated dose of dose-dense topotecan as induction chemotherapy before standard therapy (carboplatin plus etoposide alone or in combination with radiotherapy) in patients with small cell lung cancer (SCLC). PATIENTS AND METHODS: Chemotherapy-naive patients with SCLC and good performance status were eligible. Three 2-week cycles of dose-dense topotecan administered on days 1-3 with granulocyte colony-stimulating factor support were followed by four cycles of standard carboplatin plus etoposide therapy alone (extensive-stage SCLC) or with radiotherapy (limited-stage SCLC). The dose of topotecan was escalated from 1.5 mg/m2/day to 2.5 mg/m2/day in increments of 0.25 mg/m2/day within cohorts of 3-5 patients each. Dose-limiting toxicity was defined as any grade 3 or 4 toxicity resulting in a treatment reduction or a delay of >3 days. RESULTS: Twenty-two patients with SCLC (5 limited-stage, 17 extensive-stage) were enrolled. Treatment was well tolerated. The dose-limiting toxicities were thrombocytopenia and neutropenia, and the maximum tolerated dose of dose-dense topotecan induction therapy was 2.25 mg/m2/day. Overall, topotecan-related grade 3/4 haematological toxicities included neutropenia (n = 4), thrombocytopenia (n = 3) and febrile neutropenia (n = 1). No grade 4 non-haematological toxicities occurred. Grade 3 adverse events included nausea (n = 2), renal toxicity (n = 1) and anorexia (n = 1). Toxicity during the carboplatin plus etoposide +/- radiotherapy phase of therapy was consistent with that reported in previous trials. The overall response rate was 80% for limited-stage and 76% for extensive-stage SCLC. Median survival was 8 months in patients with limited-stage SCLC and 13.5 months for patients with extensive-stage SCLC. CONCLUSION: The results of this phase I study suggest that a regimen of sequential dose-dense topotecan and carboplatin plus etoposide is feasible, and the preliminary activity observed in patients with SCLC warrants further investigation at a starting dose of topotecan 2.25 mg/m2/day.