Fundamental mechanisms of telomerase action in yeasts and mammals: understanding telomeres and telomerase in cancer cells

Aberrant activation of telomerase occurs in 85-90% of all cancers and underpins the ability of cancer cells to bypass their proliferative limit, rendering them immortal. The activity of telomerase is tightly controlled at multiple levels, from transcriptional regulation of the telomerase components to holoenzyme biogenesis and recruitment to the telomere, and finally activation and processivity. However, studies using cancer cell lines and other model systems have begun to reveal features of telomeres and telomerase that are unique to cancer. This review summarizes our current knowledge on the mechanisms of telomerase recruitment and activation using insights from studies in mammals and budding and fission yeasts. Finally, we discuss the differences in telomere homeostasis between normal cells and cancer cells, which may provide a foundation for telomere/telomerase targeted cancer treatments

A comprehensive survey of genomic alterations in gastric cancer reveals systematic patterns of molecular exclusivity and co-occurrence among distinct therapeutic targets

Objective: Gastric cancer is a major gastrointestinal malignancy for which targeted therapies are emerging as treatment options. This study sought to identify the most prevalent molecular targets in gastric cancer and to elucidate systematic patterns of exclusivity and co-occurrence among these targets, through comprehensive genomic analysis of a large panel of gastric cancers. Design: Using high-resolution single nucleotide polymorphism arrays, copy number alterations were profiled in a panel of 233 gastric cancers (193 primary tumours, 40 cell lines) and 98 primary matched gastric non-malignant samples. For selected alterations, their impact on gene expression and clinical outcome were evaluated. Results: 22 recurrent focal alterations (13 amplifications and nine deletions) were identified. These included both known targets (FGFR2, ERBB2) and also novel genes in gastric cancer (KLF5, GATA6). Receptor tyrosine kinase (RTK)/RAS alterations were found to be frequent in gastric cancer. This study also demonstrates, for the first time, that these alterations occur in a mutually exclusive fashion, with KRAS gene amplifications highlighting a clinically relevant but previously underappreciated gastric cancer subgroup. FGFR2-amplified gastric cancers were also shown to be sensitive to dovitinib, an orally bioavailable FGFR/VEGFR targeting agent, potentially representing a subtype-specific therapy for FGFR2-amplified gastric cancers. Conclusion: The study demonstrates the existence of five distinct gastric cancer patient subgroups, defined by the signature genomic alterations FGFR2 (9% of tumours), KRAS (9%), EGFR (8%), ERBB2 (7%) and MET (4%). Collectively, these subgroups suggest that at least 37% of gastric cancer patients may be potentially treatable by RTK/RAS directed therapies

EORTC-1203-GITCG - the “INNOVATION”-trial: Effect of chemotherapy alone versus chemotherapy plus trastuzumab, versus chemotherapy plus trastuzumab plus pertuzumab, in the perioperative treatment of HER2 positive, gastric and gastroesophageal junction adenocarcinoma on pathologic response rate: a randomized phase II-intergroup trial of the EORTC-Gastrointestinal Tract Cancer Group, Korean Cancer Study Group and Dutch Upper GI-Cancer group

Background: 10–20% of patients with gastric cancer (GC) have HER2+ tumors. Addition of trastuzumab (T) to cisplatin/fluoropyrimidine-based chemotherapy (CT) improved survival in metastatic, HER2+ GC. When pertuzumab (P) was added to neoadjuvant T and CT, a significant increase in histopathological complete response rate was observed in HER2+ breast cancer. This study aims to investigate the added benefit of using both HER2 targeting drugs (T alone or the combination of T + P), in combination with perioperative CT for localized HER2+ GC. Methods: This is a prospective, randomized, open-label, phase II trial. HER2 status from patients with resectable GC (UICC TNM7 tumor stage Ib-III) will be centrally determined. Two hundred and-fifteen patients from 52 sites in 14 countries will be centrally randomized (1:2:2 ratio) to one of the following treatment arms: 1. Standard: CT alone. CT regimens will be FLOT (5-FU, leucovorin, oxaliplatin, taxotere) CapOx (capecitabine, oxaliplatin) or FOLFOX (5-FU, leucovorin, oxaliplatin) according to investigator’s choice in Europe, and cisplatin/capecitabine in Asia. 2. Experimental arm 1: CT as in control group, plus T (8 mg/kg loading dose, followed by 6 mg/kg every 3 weeks) at day 1, independent of CT chosen for 3 cycles of 3 weeks before and after surgery. 3. Experimental arm 2: CT plus T as in experimental arm 1, plus P (840 mg every 3 weeks) on day 1. Adjuvant treatment with T or T + P will continue for 17 cycles in total. Stratification factors are: histology (intestinal/non-intestinal); region (Asia vs Europe); location (GEJ vs non-GEJ); HER2 immunohistochemistry score (IHC 3+ vs IHC 2+/FISH+) and chemotherapy regimen. Primary objective is to detect an increase in the major pathological response rate from 25 to 45% either with CT plus T alone, or with CT plus the combination of T and P. Discussion: Depending on the results of the INNOVATION trial, the addition of HER2 targeted treatment with either T or T and P to CT may inform future study designs or become a standard in the perioperative management HER2+ GC. Trial registration: This article reports a health care intervention on human participants and was registered on July 10, 2014 under ClinicalTrials.gov identifier: NCT02205047; EudraCT: 2014–000722-38

Quantification of Alternative Splicing Variants of Human Telomerase Reverse Transcriptase and Correlations with Telomerase Activity in Lung Cancer

Telomerase plays important roles in the development and progression of malignant tumors, and its activity is primarily determined by transcriptional regulation of human telomerase reverse transcriptase (hTERT). Several mRNA alternative splicing variants (ASVs) for hTERT have been identified, but it remains unclear whether telomerase activity is directly associated with hTERT splicing transcripts. In this study, we developed novel real-time PCR protocols using molecular beacons and applied to lung carcinoma cell lines and cancerous tissues for quantification of telomerase activity and three essential hTERT deletion transcripts respectively. The results showed that lung carcinoma cell lines consistently demonstrated telomerase activity (14.22–31.43 TPG units per 100 cells) and various hTERT alternative splicing transcripts. For 165 lung cancer cases, telomerase activity showed significant correlation with tumor differentiation (poorly->moderately->well-differentiated, P<0.01) and with histotypes (combined small cell and squamous cell carcinoma>squamous cell carcinoma>adenosquamous carcinoma>adenocarcinoma, P<0.05). Although the overall hTERT transcripts were detected in all the samples, they were not associated with telomerase activity (r = 0.092, P = 0.24). Telomerase activity was significantly correlated with the transcriptional constituent ratio of α-deletion (r = -0.267, P = 0.026), β-deletion (r = -0.693, P = 0.0001) and γ-deletion (r = –0.614, P = 0.001). The positive rate and average constituent ratio of β-deletion transcripts (92.12%, 0.23) were higher than those of α-deletion (41.82%, 0.12) or γ-deletion (16.36%, 0.18) transcripts. The combined small-cell and squamous cell carcinomas expressed less deletion transcripts, especially β-deletion, than other histotypes, which might explain their higher telomerase activity. In conclusion, the molecular beacon-based real-time PCR protocols are rapid, sensitive and specific methods to quantify telomerase activity and hTERT ASVs. Telomerase activity may serve as a reliable and effective molecular marker to assist the evaluation of histological subtype and differentiation of lung carcinomas. Further studies on hTERT deletion splicing transcripts, rather than the overall hTERT transcripts, may improve our understanding of telomerase regulation

Avelumab (anti-PD-L1) as first-line switch-maintenance or second-line therapy in patients with advanced gastric or gastroesophageal junction cancer: phase 1b results from the JAVELIN Solid Tumor trial

Background We evaluated the antitumor activity and safety of avelumab, a human anti–PD-L1 IgG1 antibody, as first-line switch-maintenance (1 L-mn) or second-line (2 L) treatment in patients with advanced gastric/gastroesophageal cancer (GC/GEJC) previously treated with chemotherapy. Methods In a phase 1b expansion cohort, patients without (1 L-mn) or with (2 L) disease progression following first-line chemotherapy for advanced GC/GEJC received avelumab 10 mg/kg intravenously every 2 weeks. Endpoints included best overall response, progression-free survival (PFS), overall survival (OS), and safety. Results Overall, 150 patients were enrolled (1 L-mn, n = 90; 2 L, n = 60) and median follow-up in the 1 L-mn and 2 L subgroups was 36.0 and 33.7 months, respectively. The confirmed objective response rate was 6.7% in both subgroups (95% CI, 2.5–13.9% and 1.8–16.2%, respectively), including complete responses in 2.2% of the 1 L-mn subgroup (n = 2). In the 1 L-mn and 2 L subgroups, median duration of response was 21.4 months (95% CI, 4.0–not estimable) and 3.5 months (95% CI, 2.8–8.3) and disease control rates were 56.7 and 28.3%, respectively. Median PFS in the 1 L-mn and 2 L subgroups was 2.8 months (95% CI, 2.3–4.1) and 1.4 months (95% CI, 1.3–1.5), with 6-month PFS rates of 23.0% (95% CI, 14.7–32.4%) and 7.9% (95% CI, 2.6–17.2%), and median OS was 11.1 months (95% CI, 8.9–13.7) and 6.6 months (95% CI, 5.4–9.4), respectively. In the 1 L-mn subgroup, median OS measured from start of 1 L chemotherapy was 18.7 months (95% CI, 15.4–20.6). Across both subgroups, 20.7% had an infusion-related reaction of any grade. Other common treatment-related adverse events (TRAEs) of any grade included fatigue (10.0%) and nausea (6.7%). Treatment-related serious adverse events occurred in 4.0% of patients. Overall, 8.7% had a grade ≥3 TRAE, including 1 treatment-related death. Conclusion Avelumab showed clinical activity and an acceptable safety profile in patients with GC/GEJC

A First-Time-in-Human Study of GSK2636771, a Phosphoinositide 3 Kinase Beta-Selective Inhibitor, in Patients with Advanced Solid Tumors.

Background: The PI3K/protein kinase B (AKT) pathway is commonly activated in several tumor types. Selective targeting of p110β could result in successful pathway inhibition while avoiding the on- and off-target effects of pan-PI3K inhibitors. GSK2636771 is a potent, orally bioavailable, adenosine triphosphate-competitive, selective inhibitor of PI3Kβ.Methods: We evaluated the safety, pharmacokinetics, pharmacodynamics and antitumor activity of GSK2636771 to define the recommended phase II dose (RP2D). During the dose-selection and dose-escalation stages (parts 1 and 2), patients with PTEN-deficient advanced solid tumors received escalating doses of GSK2636771 (25-500 mg once daily) using a modified 3+3 design to determine the RP2D; tumor type-specific expansion cohorts (part 3) were implemented to further assess tumor responses at the RP2D.Results: A total of 65 patients were enrolled; dose-limiting toxicities were hypophosphatemia and hypocalcemia. Adverse events included diarrhea (48%), nausea (40%), and vomiting (31%). Single- and repeat-dose exposure increased generally dose proportionally. GSK2636771 400 mg once daily was the RP2D. Phospho/total AKT ratio decreased with GSK2636771 in tumor and surrogate tissue. A castrate-resistant prostate cancer (CRPC) patient harboring PIK3CB amplification had a partial response for over a year; an additional 10 patients derived durable (≥24 weeks) clinical benefit, including two other patients with CRPC with PIK3CB alterations (≥34 weeks). GSK2636771 400 mg once daily orally induced sufficient exposure and target inhibition with a manageable safety profile.Conclusions: Genomic aberrations of PIK3CB may be associated with clinical benefit from GSK2636771. Clin Cancer Res; 23(19); 5981-92. ©2017 AACR

Korarchaeota Diversity, Biogeography, and Abundance in Yellowstone and Great Basin Hot Springs and Ecological Niche Modeling Based on Machine Learning

Over 100 hot spring sediment samples were collected from 28 sites in 12 areas/regions, while recording as many coincident geochemical properties as feasible (>60 analytes). PCR was used to screen samples for Korarchaeota 16S rRNA genes. Over 500 Korarchaeota 16S rRNA genes were screened by RFLP analysis and 90 were sequenced, resulting in identification of novel Korarchaeota phylotypes and exclusive geographical variants. Korarchaeota diversity was low, as in other terrestrial geothermal systems, suggesting a marine origin for Korarchaeota with subsequent niche-invasion into terrestrial systems. Korarchaeota endemism is consistent with endemism of other terrestrial thermophiles and supports the existence of dispersal barriers. Korarchaeota were found predominantly in >55°C springs at pH 4.7–8.5 at concentrations up to 6.6×106 16S rRNA gene copies g−1 wet sediment. In Yellowstone National Park (YNP), Korarchaeota were most abundant in springs with a pH range of 5.7 to 7.0. High sulfate concentrations suggest these fluids are influenced by contributions from hydrothermal vapors that may be neutralized to some extent by mixing with water from deep geothermal sources or meteoric water. In the Great Basin (GB), Korarchaeota were most abundant at spring sources of pH<7.2 with high particulate C content and high alkalinity, which are likely to be buffered by the carbonic acid system. It is therefore likely that at least two different geological mechanisms in YNP and GB springs create the neutral to mildly acidic pH that is optimal for Korarchaeota. A classification support vector machine (C-SVM) trained on single analytes, two analyte combinations, or vectors from non-metric multidimensional scaling models was able to predict springs as Korarchaeota-optimal or sub-optimal habitats with accuracies up to 95%. To our knowledge, this is the most extensive analysis of the geochemical habitat of any high-level microbial taxon and the first application of a C-SVM to microbial ecology

Human telomerase activity regulation

Telomerase has been recognized as a relevant factor distinguishing cancer cells from normal cells. Thus, it has become a very promising target for anticancer therapy. The cell proliferative potential can be limited by replication end problem, due to telomeres shortening, which is overcome in cancer cells by telomerase activity or by alternative telomeres lengthening (ALT) mechanism. However, this multisubunit enzymatic complex can be regulated at various levels, including expression control but also other factors contributing to the enzyme phosphorylation status, assembling or complex subunits transport. Thus, we show that the telomerase expression targeting cannot be the only possibility to shorten telomeres and induce cell apoptosis. It is important especially since the transcription expression is not always correlated with the enzyme activity which might result in transcription modulation failure or a possibility for the gene therapy to be overcome. This review summarizes the current state of knowledge of numerous telomerase regulation mechanisms that take place after telomerase subunits coding genes transcription. Thus we show the possible mechanisms of telomerase activity regulation which might become attractive anticancer therapy targets