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S. Vari



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    MO20 - Preclinical Therapeutic Models II (ID 93)

    • Event: WCLC 2013
    • Type: Mini Oral Abstract Session
    • Track: Biology
    • Presentations: 1
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      MO20.06 - Histone deacetylase inhibition downregulates thymidylate synthase (TS) expression and enhances pemetrexed-induced cytotoxicity in NSCLC models (ID 2010)

      11:05 - 11:10  |  Author(s): S. Vari

      • Abstract
      • Presentation
      • Slides

      Background
      Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death worldwide. Pemetrexed (PEM), a multi-target folate antagonist, has demonstrated targeted efficacy in NSCLC histological subtypes characterized by low thymidylate synthase (TS, one of PEM’s molecular targets) expression. Recently, TS expression has been found to be regulated by histone acetylation status, thus raising the interesting hypothesis that histone deacetylase inhibitors (HDACi) may sensitize NSCLC cells to PEM cytotoxicity.

      Methods
      Molecular and functional effects of single and combined HDAC inhibition and PEM exposure were assessed in NSCLC cell lines (A549, H1299, H1650, Calu-1) and patient-derived lung cancer stem cells (L-CSC). Pharmacologic interactions were assessed by conservative isobologram analysis using the Chou-Talalay method and the Calcusyn software. TS expression was studied by WB analysis and real-time PCR. Apoposis induction was assessed by flow cytometry and WB. Autophagy was assessed by analysis of autophagosome formation in EGFP-LC3B expressing cells, detection of acidic vesicle organelles (AVO) formation and WB. In vivo experiments were conducted in xenograft models established by i.m. injection of NSCLC cells into 6-8 week-old male athymic mice (nu/nu).

      Results
      In NSCLC cell lines and L-CSC, the HDACi ITF2357 dose-dependently inhibited cell growth (IC~50~: <1-20 mM), induced histone H3 acetylation, and downregulated TS expression at the mRNA and protein levels. Combined HDAC inhibition and PEM exposure was then tested using three different administration schedules: simultaneous exposure to both drugs, ITF2357 followed by PEM, and the reverse sequence. Simultaneous PEM/ITF2357 treatment resulted in antagonistic growth inhibitory interactions (combination index – CI >1) in all cell lines tested, while ITF2357 followed by PEM had additive effects in A549 cells and slightly synergistic effects in H1299 and Calu-1 cells; conversely, PEM followed by ITF2357 had strikingly synergistic effects (CI <<1) in all NSCLC cell lines, as well as in the L-CSC143. Most notably, only the ITF2357 followed by PEM sequence synergistically induced apoptosis, resulting in approximately 50% Annexin V-positive cells; apoptosis was only partially rescued by caspase inhibition by z-VAD-fmk, which led us to investigate autophagy as an alternative mechanism of combination-induced cell death. Indeed, ITF2357, and to a significantly greater extent PEM followed by ITF2357, induced autophagy as evidenced by AVO formation, LC3BII processing, p62 downregulation, and Beclin1 induction. Most importantly, autophagy induction was instrumental to the cytotoxic interaction between PEM and ITF2357, as Beclin1 silencing by shRNA completely reversed their growth inhibitory synergism and prevented both autophagy and apoptosis induction. The synergistic cytotoxic interaction between PEM and ITF2357 was at least partly due to ITF2357 ability to prevent PEM-induced TS upregulation, as TS silencing by siRNA further enhanced apoptosis induction by single and combined PEM/ITF2357 exposure. Finally, both H1650 and H1299 xenografts had a robust response to sequential PEM/ITF2357 administration in vivo, resulting in an approximately doubled mice survival in the H1650 model.

      Conclusion
      Overall, our data indicate that HDAC inhibition by ITF2357 downregulates TS expression and synergistically potentiates apoptosis and autophagy induction following PEM exposure, supporting the clinical investigation of sequential PEM/ITF2357 schedules for the treatment of advanced NSCLC.

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    P1.11 - Poster Session 1 - NSCLC Novel Therapies (ID 208)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Medical Oncology
    • Presentations: 1
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      P1.11-033 - Afatinib in EGFR mutant non-small-cell lung cancer patients with acquired resistance to reversible EGFR-TKIs (ID 2285)

      09:30 - 09:30  |  Author(s): S. Vari

      • Abstract

      Background
      Afatinib, an irreversible EGFR-HER2 dual inhibitor, demonstrated superiority versus standard platinum-based chemotherapy as front-line therapy in non-small-cell lung cancer patients (NSCLC) with activating Epidermal Growth Factor Receptor (EGFR) mutations. In pretreated NSCLC afatinib failed to improve survival when compared to placebo in patients refractory to gefitinib or erlotinib and not selected for EGFR status. Aim of the present study was to evaluate clinical efficacy of afatinib in EGFR mutant NSCLC patients (pts) with secondary resistance to reversible EGFR-TKIs.

      Methods
      We retrospectively analyzed a cohort of 97 EGFR mutant lung cancer pts resistant to EGFR-TKI according to criteria used in the LUX-Lung 1 trial (Miller VA, Lancet Oncol 2012) and treated with Afatinib at the daily dose of 40-50 mg. The drug was given as compassionate use.

      Results
      The study included individuals with a median age of 62,5 year. The majority were females (N=63/64.9%), never/former smokers (N=94/96,9%), with good performance status (ECOG PS 0-1; N=90/90.2%) and pretreated with > 3 therapy lines (N=68/70.0%). EGFR status was assessed in tumor tissue obtained at the time of original diagnosis. The majority of pts (N=64, 66%) harbored a deletion in exon 19, while T790M mutation was detected in two cases including one case with double exon 19 and T790M mutation. Among the 95 pts evaluable for toxicity, 54.7% had any grade skin rash, including 11.6% with grade 3, and 50,5% had any grade of diarrhea, with grade 3 recorded in 10,5%. Among the 87 pts evaluable for efficacy, response rate (RR) was 11.5%, with a median progression free-survival and overall survival of 3.9 months and 7.3 months respectively. In 25 pts a tumor biopsy was repeated immediately before starting Afatinib therapy and 1 patient out of 5 individuals harboring T790M mutation showed a short extracerebral partial response, with following brain progression.

      Conclusion
      Our findings suggest that afatinib is modestly effective in EGFR mutant NSCLC with acquired resistance to reversible EGFR-TKIs.

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    P3.06 - Poster Session 3 - Prognostic and Predictive Biomarkers (ID 178)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Biology
    • Presentations: 1
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      P3.06-026 - Thymidylate synthase (TS) mRNA and protein expression in advanced non-small cell lung cancer (NSCLC) patients treated with pemetrexed-based therapy. (ID 2355)

      09:30 - 09:30  |  Author(s): S. Vari

      • Abstract

      Background
      In NSCLC, higher Thymidylate Synthase (TS) levels have been reported in both squamous and large cell carcinomas compared to adenocarcinoma. In clinical practice, Pemetrexed, a potent antifolate inhibitor of TS, showed a selective benefit in patients with "non-squamous" NSCLC. Two retrospective studies have shown that low TS protein levels are associated with better clinical outcome in NSCLC patients treated with pemetrexed. Aim of this study was to explore, in a series of advanced stage IV patients receiving pemetrexed-based regimens in first line of treatment, the association between TS mRNA and protein expression with overall survival (OS) and therapeutic response.

      Methods
      Two series of histologically confirmed non squamous-NSCLC, assessed in formalin-fixed and paraffin embedded specimens from patients treated with pemetrexed-based regimens were collected: the first series at San Luigi Hospital (n=64), the second series at Regina Elena National Cancer Institute (n=8). Due to the limited amounts of tissue specimens available, total RNA extraction was possible in 52 out of 72 cases. TS protein expression was performed using immunohistochemistry (mouse monoclonal TS106 antibody) and scored through H-SCORE method, considering both staining intensity (0 no staining; +1 weak; +2 moderate; or +3 strong) and percentage of tumor cells stained, resulting in semiquantitative H-scores ranging from 0 to 300. TS nuclear and cytoplasmic staining, respectively, were separately scored. Statistical analyses were performed using the STATISTICA10 software.

      Results
      The differential H-SCORE assessment showed a strong importance of TS localisation for clinical outcome prediction: in Cox regression analysis, a statistically significant association was observed between nuclear TS expression and OS (p < 0.009) indicating that lower nuclear TS expression levels were associated with longer OS. In addition, lower nuclear TS levels were significantly associated with a better response to therapy (p<0.001). On the contrary, TS cytoplasmic staining did not affect patients’ survival or clinical response (p>0.05). Four subgroups of patients, based on the dichotomized low/high TS expression in both nucleus and cytoplasm, were obtained: both high, both low, nucleus high/cytoplasm low and nucleus low/cytoplasm high. Significant differences in overall survival among these four groups were detected (p=0.017), confirming the strong and selective influence of nuclear TS, as compared to cytoplasmic TS, expression in clinical outcome. Moreover, Chi[2] test revealed a significant association between low nuclear TS and partial response to pemetrexed treatment, independently of cytoplasmic TS expression (p<0.001). No correlation between TS protein expression data and clinico-pathological data (age, gender) were identified. TS gene expression analyses are ongoing.

      Conclusion
      This retrospective study suggests that TS protein expression, selectively assessed at nuclear level, has a potential predictive role in advanced stage IV patients, receiving pemetrexed in first line of treatment. Patients with low nuclear TS expression showed prolonged overall survival and better response to therapy. Such preliminary results define TS assessment as a potential tool which may select the most appropriate group of patients to be treated with pemetrexed.