Impaired telomere maintenance in Alazami syndrome patients with LARP7 deficiency.

BACKGROUND: Loss of function in genes required for telomere maintenance result in disorders known as telomeropathies, which are characterized by a pattern of symptoms including generalized and specific lymphocytopenias as well as very short telomere length and disease anticipation. METHODS: Because human LARP7 is the most likely ortholog of the Tetrahymena p65 protein, which is required for telomerase activity in that organism, we investigated the effects of LARP7 silencing in human cells as well as in two distinct families with Alazami syndrome (loss of function of LARP7). RESULTS: Depletion of LARP7 caused a reduction in telomerase enzymatic activity and progressively shorter telomeres in human cancer cell lines. Alazami syndrome patients from two separate cohorts exhibited very short lymphocyte telomeres. Further, wild-type offspring of LARP7 mutant individuals also had very short telomeres, comparable to what is observed in telomerase (hTERT) mutant cohorts. CONCLUSIONS: Together, these experiments demonstrate that in addition to the readily apparent developmental disorder associated with LARP7 deficiency, an underlying telomeropathy exists even in unaffected siblings of these individuals.

[Pharmacological characteristics and clinical study results of the first RAS inhibitor sotorasib (LUMAKRAS®) for non-small cell lung cancer with KRAS G12C mutation].

Sotorasib (LUMAKRAS®) is the first RAS inhibitor that selectively binds to KRAS G12C and irreversibly inhibits the conformational change from the inactive to active form of KRAS. The gene mutation that produces KRAS G12C protein, which is the target of sotorasib, is one of the oncogenic drivers observed in non-small cell lung cancer (NSCLC), and the KRAS G12C mutation causes conformational changes to maintain KRAS in an active form enhancing downstream signals, leading to tumor cell proliferation and survival. Although the role of KRAS in human cancers has been known for decades, role of RAS in normal cells, the high affinity between RAS and GTP, high concentration of intracellular GTP, and the smooth surface of RAS protein makes it difficult to develop drugs targeting RAS mutation for a long time. However, the discovery of the Switch II pocket of KRAS in 2013 and the report of compounds that specifically bind to KRAS G12C led to the development of sotorasib. Sotorasib inhibited the growth of KRAS G12C positive cell lines and suppressed tumor growth in a mouse model implanted with the KRAS G12C positive cell line. In clinical trials, objective responses were seen in 37.4% of patients with KRAS G12C positive advanced NSCLC taking 960mg sotorasib orally per day. There were no dose-limiting toxicities and other adverse events were tolerable. Sotorasib was designated as an orphan drug in March 2021 and approved in January 2022 for KRAS G12C positive unresectable/recurrent NSCLC that has progressed after 1st line therapy in Japan.

Quantitative telomeric overhang determination using a double-strand specific nuclease.

Telomeres terminate in 3' overhangs that function in end protection and the formation of t-loops. Determining the steps and factors involved in overhang processing is compromised by the inability to easily and accurately determine overhang size in the presence of many kilobases of double-stranded telomeric DNA. We here describe the use of a double-strand specific nuclease (DSN) that entirely digests double-stranded DNA including telomeres, leaving the overhangs intact so that they can be measured.

Real-world effectiveness and safety of nivolumab in patients with non-small cell lung cancer: A multicenter retrospective observational study in Japan.

OBJECTIVES: To describe the treatment patterns and determine the effectiveness and safety of nivolumab treatment for non-small cell lung cancer (NSCLC) in real-world setting in Japan. MATERIALS AND METHODS: Japanese patients with NSCLC who received nivolumab were analyzed retrospectively. Patients who had started nivolumab treatment between April 2016 and December 2016 were enrolled. Information regarding patient demographics and clinical backgrounds, treatment patterns from diagnosis to post-nivolumab treatment, effectiveness and safety of nivolumab treatment and that of treatments just before and after nivolumab treatment, and programmed death-ligand 1 (PD-L1) expression status, if available, were collected. Factors associated with nivolumab effectiveness identified by univariate and multivariate analyses were further investigated for plotting Kaplan-Meier curves of epidermal growth factor receptor (EGFR) gene mutation status, PD-L1 expression status, and Eastern Cooperative Oncology Group performance status (ECOG PS). RESULTS: In this study, 901 NSCLC patients were enrolled. Nivolumab was used the most as a second line treatment with a median number of nivolumab doses of five. The median overall survival (OS) was 14.6 months, one-year survival rate was 54.3 %, and median progression-free survival (PFS) was 2.1 months. The objective response rate was 20.5 % and disease control rate was 57.4 %. According to multivariate analyses, better OS and PFS were associated with favorable ECOG PS and absence of liver metastasis. Better PFS was observed in patients without EGFR mutation and patients with smoking history. PFS and best overall response in PD-L1 expression subgroups were expression level-dependent. The overall incidence of irAEs was 45.8 %, and the incidence of adverse events of grade 3 or higher was 14.0 %. CONCLUSION: The real-world effectiveness and safety of nivolumab is consistent with that reported by previous clinical trials and other real-world data. Subgroup analysis showed that ECOG PS, EGFR mutation status, smoking status, and PD-L1 were associated with the effectiveness of nivolumab.

Nivolumab treatment of elderly Japanese patients with non-small cell lung cancer: subanalysis of a real-world retrospective observational study (CA209-9CR).

OBJECTIVES: We conducted a subanalysis of data from the multicentre, retrospective observational Nivolumab Japan Real World (CA209-9CR) study to evaluate nivolumab effectiveness and safety in elderly patients (aged ≥75 years) with advanced/metastatic non-small cell lung cancer. MATERIALS AND METHODS: Medical record data of patients initiating nivolumab treatment between April 2016 and December 2016 were collected using electronic data capture from 23 cancer hospitals in Japan between March 2017 and August 2018. Nivolumab treatment data were collected to investigate the treatment patterns by age group (<75 and ≥75 years), and the effectiveness and safety of nivolumab treatment. RESULTS: Of the 901 patients evaluated, 178 (19.8%) were aged ≥75 years. Overall, patients received a median of five nivolumab treatments regardless of age group. Comparable progression-free survival was observed, with a median of 2.1 months in patients aged <75 years and 2.1 months in patients aged ≥75 years (p=0.5441). No significant differences were found in duration of response, overall response rate or disease control rate between the two age groups. Median overall survival in patients aged <75 and ≥75 years was 14.7 months and 12.3 months, respectively. Grade ≥3 adverse events (AEs) occurred in 29.2% and 28.1% of patients aged <75 and ≥75 years, respectively. Immune-related AEs decreased slightly with increasing age; time to onset and rates of improvement were similar for patients aged <75 and ≥75 years. The most common grade 3-4 AEs were interstitial lung disease in both age groups (4.0% in patients aged <75 years and 2.8% in those aged ≥75 years). Poor performance status was associated with worse outcomes in both age groups. CONCLUSION: Based on Japanese real-world data, the effectiveness and safety of nivolumab were confirmed regardless of age.

The roles of telomerase in the generation of polyploidy during neoplastic cell growth.

Polyploidy contributes to extensive intratumor genomic heterogeneity that characterizes advanced malignancies and is thought to limit the efficiency of current cancer therapies. It has been shown that telomere deprotection in p53-deficient mouse embryonic fibroblasts leads to high rates of polyploidization. We now show that tumor genome evolution through whole-genome duplication occurs in ∼15% of the karyotyped human neoplasms and correlates with disease progression. In a panel of human cancer and transformed cell lines representing the two known types of genomic instability (chromosomal and microsatellite), as well as the two known pathways of telomere maintenance in cancer (telomerase activity and alternative lengthening of telomeres), telomere dysfunction-driven polyploidization occurred independently of the mutational status of p53. Depending on the preexisting context of telomere maintenance, telomerase activity and its major components, human telomerase reverse transcriptase (hTERT) and human telomerase RNA component (hTERC), exert both reverse transcriptase-related (canonical) and noncanonical functions to affect tumor genome evolution through suppression or induction of polyploidization. These new findings provide a more complete mechanistic understanding of cancer progression that may, in the future, lead to novel therapeutic interventions.

Development of methods for quantitative comparison of pooled shRNAs by mass sequencing.

Pooled short-hairpin RNA (shRNA) library screening is a powerful tool for identifying a set of genes in biological pathways that require stable expression to produce a desired phenotype. Massive parallel sequencing of half-hairpins has proven highly variable and has not given satisfactory results concerning the relative abundance of different shRNAs before and after selection. Here, the authors describe a method for quantitative comparison of half-hairpins from pooled shRNAs in the mir30-based pGIPZ vector that is analyzed by massive parallel sequencing. Introducing a multiplexing code and refining the sample preparation scheme resulted in the predicted ability to detect twofold enrichments. These improvements should permit half-hairpin sequencing to analyze either dropout screens or selective pooled shRNA screens of limited stringency to analyze phenotypes not accessible in transient experiments.

The involvement of the Mre11/Rad50/Nbs1 complex in the generation of G-overhangs at human telomeres.

A central function of telomeres is to prevent chromosome ends from being recognized as DNA double-strand breaks (DSBs). Several proteins involved in processing DSBs associate with telomeres, but the roles of these factors at telomeres are largely unknown. To investigate whether the Mre11/Rad50/Nbs1 (MRN) complex is involved in the generation of proper 3' G-overhangs at human telomere ends, we used RNA interference to decrease expression of MRN and analysed their effects. Reduction of MRN resulted in a transient shortening of G-overhang length in telomerase-positive cells. The terminal nucleotides of both C- and G-rich strands remain unaltered in Mre11-diminished cells, indicating that MRN is not responsible for specifying the final end-processing event. The reduction in overhang length was not seen in telomerase-negative cells, but was observed after the expression of exogenous telomerase, which suggested that the MRN complex might be involved in the recruitment or action of telomerase.