Fabio Conforti

Molecular Pathways: Anticancer Activity by Inhibition of Nucleocytoplasmic Shuttling

A dynamic distribution between nucleus and cytoplasm (nucleocytoplasmic shuttling) is one of the control mechanisms adapted by normal cells to regulate the activity of a variety of molecules. Growing evidence suggests that dysregulation of the nucleocytoplasmic shuttling is involved in promoting abnormal cell survival, tumor progression, and drug resistance, and is associated with poor cancer prognosis. Aberrant nucleocytoplasmic shuttling in cancer cells may result from a hyperactive status of diverse signal-transduction pathways, such as the PI3K–AKT and MAPK pathways, or from alterations in the general nuclear import/export machinery. Among the large number of molecules involved in the shuttling process, exportin XPO1, also known as chromosome region maintenance 1, appears to play a particularly prominent role in pathogenesis of both hematological malignancies and solid tumors. Given the importance of nucleocytoplasmic shuttling in cancer pathogenesis and the rapidly expanding knowledge in this field, attempts have been made to develop compounds able to revert the aberrant nucleocytoplasmic shuttling. A promising new drug, KPT-330 (Selinexor), which belongs to the class of XPO1 inhibitors called selective inhibitors of nuclear export, is now being tested in phase I/II clinical trials. Clin Cancer Res; 21(20); 4508–13. ©2015 AACR.

Phase II Study of Everolimus in Patients With Thymoma and Thymic Carcinoma Previously Treated With Cisplatin-Based Chemotherapy

Purpose No effective salvage treatments are available for patients with advanced/recurrent thymoma (T) or thymic carcinoma (TC) who have progressed after platinum-based chemotherapy. This study evaluated the activity of everolimus in patients with advanced/recurrent T or TC previously treated with cisplatin-containing chemotherapy. Patients and Methods This was a single-arm, single-stage, open-label, multicenter, phase II trial. Patients received oral everolimus 10 mg/d until disease progression, unacceptable toxicity, or patient refusal. A Fleming phase II trial was designed. The null hypothesis of a true disease control rate (DCR) of 40% was tested against a one-sided alternative of a true DCR of 60% (α = β = 0.10): If disease control were achieved in ≥ 21 of the first 41 evaluable patients, everolimus could be recommended for further evaluation. Progression-free survival, overall survival, and safety were also evaluated. Results From 2011 to 2013, 51 patients were enrolled (T, n = 32; TC, n = 19). Complete remission was observed in one patient with TC, partial response in five patients (T, n = 3; TC, n = 2), and stable disease in 38 patients (T, n = 27; TC, n= 11), with a DCR of 88% (T,: 93.8%; TC, 77.8%). With a median follow up of 25.7 months, median progression-free survival was 10.1 months (T,: 16.6 months; TC, 5.6 months), and median overall survival was 25.7 months (T, not reached; TC, 14.7 months). Fourteen patients had a serious drug-related adverse event; of these patients, nine permanently discontinued treatment. Three patients died of pneumonitis while in the study. Immunohistochemical positivity for p4E-BP1 or insulin-like growth factor-1 receptor was statistically significantly related to a shorter survival. Conclusion Everolimus may induce durable disease control in a high percentage of patients with T or TC, albeit with a potential high risk of fatal pneumonitis.

PI3K as a Potential Therapeutic Target in Thymic Epithelial Tumors.

Introduction: Thymic epithelial tumors (TETs) are rare tumors originating from the epithelium of the thymus with limited therapeutic options beyond surgery. The pathogenesis of TETs is poorly understood, and the scarcity of model systems for these rare tumors makes the study of their biology very challenging. Methods: A new cell line (MP57) was established from a thymic carcinoma specimen and characterized using standard biomarker analysis, as well as next‐generation sequencing (NGS) and functional assays. Sanger sequencing was used to confirm the mutations identified by NGS. Results: MP57 possesses all the tested thymic epithelial markers and is deemed a bona fide thymic carcinoma cell line. NGS analysis of MP57 identified a mutation in the gene PIK3R2, which encodes a regulatory subunit of PI3K. Further analysis identified different mutations in multiple PI3K subunit genes in another cell line and several primary thymic carcinoma samples, including two catalytic subunits (PIK3CA and PIK3CG) and another regulatory subunit (PIK3R4). Inhibiting PI3K with GDC‐0941 resulted in in vitro antitumor activity in TET cells carrying mutant PI3K subunits. Conclusions: Alterations of PI3K due to mutations in its catalytic or regulatory subunits are observed in a subgroup of TETs, in particular, thymic carcinomas. Targeting PI3K may be an effective strategy to treat these tumors.

Therapeutic effects of XPO1 inhibition in thymic epithelial tumors

Exportin 1 (XPO1) mediates nuclear export of many cellular factors known to play critical roles in malignant processes, and selinexor (KPT-330) is the first XPO1-selective inhibitor of nuclear export compound in advanced clinical development phase for cancer treatment. We demonstrated here that inhibition of XPO1 drives nuclear accumulation of important cargo tumor suppressor proteins, including transcription factor FOXO3a and p53 in thymic epithelial tumor (TET) cells, and induces p53-dependent and -independent antitumor activity in vitro Selinexor suppressed the growth of TET xenograft tumors in athymic nude mice via inhibition of cell proliferation and induction of apoptosis. Loss of p53 activity or amplification of XPO1 may contribute to resistance to XPO1 inhibitor in TET. Using mass spectrometry-based proteomics analysis, we identified a number of proteins whose abundances in the nucleus and cytoplasm shifted significantly following selinexor treatment in the TET cells. Furthermore, we found that XPO1 was highly expressed in aggressive histotypes and advanced stages of human TET, and high XPO1 expression was associated with poorer patient survival. These results underscore an important role of XPO1 in the pathogenesis of TET and support clinical development of the XPO1 inhibitor for the treatment of patients with this type of tumors. Cancer Res; 77(20); 5614-27. ©2017 AACR.

Molecular features and clinical outcome of lung malignancies in very young people.

INTRODUCTION We describe the clinical features, outcome and incidence of druggable targets of lung cancers in patients ≤ 40 years old. MATERIALS & METHODS Young patients were compared with two other groups (41-64 and ≥ 65 years). Neuroendocrine tumors, adenocarcinoma and non-adenocarcinoma/unspecified non-small-cell lung cancer were analyzed separately. Molecular characteristics of adenocarcinoma were evaluated in a subset of young patients. RESULTS Of 2847 patients with lung cancer, 100 were ≤ 40 years old. The young group contained more women, never-smokers and patients presenting with advanced disease. The commonest tumor in young patients was adenocarcinoma. In total, 19 of 34 young patients with adenocarcinoma had tumors with specific molecular alterations. CONCLUSION Lung cancers in young patients have distinctive features but outcomes similar to those in older patients.

Antitumor activity of sorafenib and imatinib in a patient with thymic carcinoma harboring c-KIT exon 13 missense mutation K642E

We report the case of a man with an advanced nonkeratinizing squamous cell thymic carcinoma harboring c-KIT exon 13 missense mutation K642E. This aberration is rare and has never been described previously in patients with thymic cancers. It has been found in a small number of cases of gastrointestinal stromal tumor and also in several cases of acral and mucosal melanomas. Some of the patients with gastrointestinal stromal tumor or melanoma harboring this rare mutation have had a tumor response when treated with imatinib. In contrast, in our case, the mutation was associated with primary resistance to full doses of imatinib but, at the same time, it was not a cause of resistance to sorafenib.