Esophageal squamous cell carcinoma (ESCC) is prevalent worldwide and particularly common in certain regions of Asia. Here we report the whole-exome or targeted deep sequencing of 139 paired ESCC cases, and analysis of somatic copy number variations (SCNV) of over 180 ESCCs. We identified previously uncharacterized mutated genes such as FAT1, FAT2, ZNF750 and KMT2D, in addition to those already known (TP53, PIK3CA and NOTCH1). Further SCNV evaluation, immunohistochemistry and biological analysis suggested their functional relevance in ESCC. Notably, RTK-MAPK-PI3K pathways, cell cycle and epigenetic regulation are frequently dysregulated by multiple molecular mechanisms in this cancer. Our approaches also uncovered many druggable candidates, and XPO1 was further explored as a therapeutic target because it showed both gene mutation and protein overexpression. Our integrated study unmasks a number of novel genetic lesions in ESCC and provides an important molecular foundation for understanding esophageal tumors and developing therapeutic targets.

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Genomic and molecular characterization of esophageal squamous cell carcinoma

Valproic acid (VPA), a branched short-chain fatty acid, is widely used as an antiepileptic drug and a mood stabilizer. Antiepileptic properties have been attributed to inhibition of Gamma Amino Butyrate (GABA) transaminobutyrate and of ion channels. VPA was recently classified among the Histone Deacetylase Inhibitors, acting directly at the level of gene transcription by inhibiting histone deacetylation and making transcription sites more accessible. VPA is a widely used drug, particularly for children suffering from epilepsy. Due to the increasing number of clinical trials involving VPA, and interesting results obtained, this molecule will be implicated in an increasing number of therapies. However side effects of VPA are substantially described in the literature whereas they are poorly discussed in articles focusing on its therapeutic use. This paper aims to give an overview of the different clinical-trials involving VPA and its side effects encountered during treatment as well as its molecular properties.

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Molecular and therapeutic potential and toxicity of valproic acid.

Background Selinexor, a selective inhibitor of nuclear export compound that blocks exportin 1 (XPO1) and forces nuclear accumulation and activation of tumor suppressor proteins, inhibits n...

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Oral selinexor-dexamethasone for triple-class refractory multiple myeloma

Reversible acetylation mediated by histone deacetylases (HDACs) influences a broad repertoire of physiological processes, many of which are aberrantly controlled in tumor cells. As HDAC inhibition prompts tumor cells to enter apoptosis, small-molecule HDAC inhibitors have been developed as a new class of mechanism-based anti-cancer agent, many of which have entered clinical trials. Although the clinical picture is evolving and the precise utility of HDAC inhibitors remains to be determined, it is noteworthy that certain tumor types undergo a favorable response, in particular hematological malignancies. Vorinostat and romidepsin have been approved for treating cutaneous T-cell lymphoma in patients with progressive, persistent or recurrent disease. Here, we discuss developments in our understanding of molecular events that underlie the anti-cancer effects of HDAC inhibitors and relate this information to the emerging clinical picture for the application of these inhibitors in the treatment of cancer.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1038/icb.2011.100

HDAC inhibitors in cancer biology: emerging mechanisms and clinical applications

Heritable changes in gene expression that are not based upon alterations in the DNA sequence are defined as epigenetics. The most common mechanisms of epigenetic regulation are the methylation of CpG islands within the DNA and the modification of amino acids in the N-terminal histone tails. In the last years, it became evident that the onset of cancer and its progression may not occur only due to genetic mutations but also because of changes in the patterns of epigenetic modifications. In contrast to genetic mutations, which are almost impossible to reverse, epigenetic changes are potentially reversible. This implies that they are amenable to pharmacological interventions. Therefore, a lot of work in recent years has focussed on the development of small molecule enzyme inhibitors like DNA-methyltransferase inhibitors or inhibitors of histone-modifying enzymes. These may reverse misregulated epigenetic states and be implemented in the treatment of cancer or other diseases, e.g., neurological disorders. Today, several epigenetic drugs are already approved by the FDA and the EMEA for cancer treatment and around ten histone deacetylase (HDAC) inhibitors are in clinical development. This review will give an update on recent clinical trials of the HDAC inhibitors used systemically that were reported in 2009 and 2010 and will present an overview of different biomarkers to monitor the biological effects.

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Histone deacetylase (HDAC) inhibitors in recent clinical trials for cancer therapy

Nuclear export of proteins and drug resistance in cancer

Inhibition of CRM1-dependent nuclear export sensitizes malignant cells to cytotoxic and targeted agents

Purpose: The novel topoisomerase I inhibitor karenitecin (KTN) shows activity against melanoma. We examined whether histone deacetylase inhibition could potentiate the DNA strand cleavage, cytotoxicity as well as the clinical toxicity, and efficacy of KTN in melanoma. Experimental Design: Apoptosis, COMET, and xenograft experiments were carried out as described previously. A phase I/II trial of valproic acid (VPA) and KTN was conducted in patients with stage IV melanoma, with any number of prior therapies, Eastern Cooperative Oncology Group performance status 0-2, and adequate organ function. Results: VPA pretreatment potentiated KTN-induced apoptosis in multiple melanoma cell lines and in mouse A375 xenografts. VPA increased KTN-induced DNA strand breaks. In the phase I/II trial, 39 patients were entered, with 37 evaluable for toxicity and 33 evaluable for response. Somnolence was the dose-limiting toxicity. The maximum tolerated dose for VPA was 75 mg/kg/d; at maximum tolerated dose, serum VPA was ∼200 μg/mL (1.28 mmol/L). At the dose expansion cohort, 47% (7 of 15) of patients had stable disease; median overall survival and time to progression were 32.8 and 10.2 weeks, respectively. Histone hyperacetylation was observed in peripheral blood mononuclear cells at maximum tolerated dose. Conclusion: VPA potentiates KTN-induced DNA strand breaks and cytotoxicity. VPA can be combined at 75 mg/kg/d for 5 days with full-dose KTN without overlapping toxicities. In metastatic poor prognosis melanoma, this combination is associated with disease stabilization in 47% of patients. Further testing of this combination appears warranted.

https://clincancerres.aacrjournals.org/content/clincanres/15/7/2479.full.pdf

Potentiation of a topoisomerase I inhibitor, karenitecin, by the histone deacetylase inhibitor valproic acid in melanoma: translational and phase I/II clinical trial.

Topoisomerase IIalpha (topo IIalpha) is exported from the nucleus of human myeloma cells by a CRM1-dependent mechanism at cellular densities similar to those found in patient bone marrow. When topo IIalpha is trafficked to the cytoplasm, it is not in contact with the DNA; thus, topo IIalpha inhibitors are unable to induce DNA-cleavable complexes and cell death. Using a CRM1 inhibitor or a CRM1-specific small interfering RNA (siRNA), we were able to block nuclear export of topo IIalpha as shown by immunofluorescence microscopy. Human myeloma cell lines and patient myeloma cells isolated from bone marrow were treated with a CRM1 inhibitor or CRM1-specific siRNA and exposed to doxorubicin or etoposide at high cell densities. CRM1-treated cell lines or myeloma patient cells were 4-fold more sensitive to topo II poisons as determined by an activated caspase assay. Normal cells were not significantly affected by CRM1-topo II inhibitor combination treatment. Cell death was correlated with increased DNA double-strand breaks as shown by the comet assay. Band depletion assays of CRM1 inhibitor-exposed myeloma cells showed increased topo IIalpha covalently bound to DNA. Topo IIalpha knockdown by a topo IIalpha-specific siRNA abrogated the CRM1-topo II therapy synergistic effect. These results suggest that blocking topo IIalpha nuclear export sensitizes myeloma cells to topo II inhibitors. This method of sensitizing myeloma cells suggests a new therapeutic approach to multiple myeloma.

https://cancerres.aacrjournals.org/content/canres/69/17/6899.full.pdf

Human Multiple Myeloma Cells Are Sensitized to Topoisomerase II Inhibitors by CRM1 Inhibition

// Joel G Turner 1 , Trinayan Kashyap 2 , Jana L Dawson 1 , Juan Gomez 1 , Alexis A Bauer 1 , Steven Grant 3 , Yun Dai 3 , Kenneth H Shain 1, 4 , Mark Meads 1 , Yosef Landesman 2 , Daniel M Sullivan 1, 5 1 Chemical Biology and Molecular Medicine Program, H Lee Moffitt Cancer Center and Research Institute, Tampa, FL, USA 2 Karyopharm Therapeutics, Natick, MA, USA 3 Massey Cancer Center, Virginia Commonwealth University, Richmond, VA, USA 4 Department of Malignant Hematology, H Lee Moffitt Cancer Center and Research Institute, Tampa, FL, USA 5 Department of Blood & Marrow Transplantation, H Lee Moffitt Cancer Center and Research Institute, Tampa, FL, USA Correspondence to: Daniel M Sullivan, email: dansullivan@moffittorg Keywords: XPO1, bortezomib, carfilzomib, multiple myeloma, acquired drug resistance Received: July 26, 2016      Accepted: October 12, 2016      Published: October 28, 2016 ABSTRACT Acquired proteasome-inhibitor (PI) resistance is a major obstacle in the treatment of multiple myeloma (MM) We investigated whether the clinical XPO1-inhibitor selinexor, when combined with bortezomib or carfilzomib, could overcome acquired resistance in MM PI-resistant myeloma cell lines both in vitro and in vivo and refractory myeloma patient biopsies were treated with selinexor/bortezomib or carfilzomib and assayed for apoptosis Mechanistic studies included NFκB pathway protein expression assays, immunofluorescence microscopy, ImageStream flow-cytometry, and proximity-ligation assays IκBα knockdown and NFκB activity were measured in selinexor/bortezomib-treated MM cells We found that selinexor restored sensitivity of PI-resistant MM to bortezomib and carfilzomib Selinexor/bortezomib treatment inhibited PI-resistant MM tumor growth and increased survival in mice Myeloma cells from PI-refractory MM patients were sensitized by selinexor to bortezomib and carfilzomib without affecting non-myeloma cells Immunofluorescence microscopy, Western blot, and ImageStream analyses of MM cells showed increases in total and nuclear IκBα by selinexor/bortezomib Proximity ligation found increased IκBα-NFκB complexes in treated MM cells IκBα knockdown abrogated selinexor/bortezomib-induced cytotoxicity in MM cells Selinexor/bortezomib treatment decreased NFκB transcriptional activity Selinexor, when used with bortezomib or carfilzomib, has the potential to overcome PI drug resistance in MM Sensitization may be due to inactivation of the NFκB pathway by IκBα

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XPO1 inhibitor combination therapy with bortezomib or carfilzomib induces nuclear localization of IκBα and overcomes acquired proteasome inhibitor resistance in human multiple myeloma

Jana L. Dawson

Papers

Nuclear export of proteins and drug resistance in cancer

Inhibition of CRM1-dependent nuclear export sensitizes malignant cells to cytotoxic and targeted agents

Potentiation of a topoisomerase I inhibitor, karenitecin, by the histone deacetylase inhibitor valproic acid in melanoma: translational and phase I/II clinical trial.

Human Multiple Myeloma Cells Are Sensitized to Topoisomerase II Inhibitors by CRM1 Inhibition

XPO1 inhibitor combination therapy with bortezomib or carfilzomib induces nuclear localization of IκBα and overcomes acquired proteasome inhibitor resistance in human multiple myeloma