The novel HDAC inhibitor AR-42-induced anti-colon cancer cell activity is associated with ceramide production

Anticancer Study of a Novel Pan-HDAC Inhibitor MPT0G236 in Colorectal Cancer Cells

Colorectal cancer (CRC) is one of the most commonly diagnosed malignancies and a leading cause of cancer worldwide. Histone deacetylases (HDACs), which regulate cell proliferation and survival, are associated with the development and progression of cancer. Moreover, HDAC inhibitors are promising therapeutic targets, with five HDAC inhibitors approved for cancer treatment to date. However, their safety profile necessitates the exploration of well-tolerated HDAC inhibitors that can be used in cancer therapeutic strategies. In this study, the pan-HDAC inhibitor MPT0G236 reduced the viability and inhibited the proliferation of human colorectal cancer cells, and normal human umbilical vein endothelial cells (HUVECs) showed reduced sensitivity. These findings indicated that MPT0G236 specifically targeted malignant tumor cells. Notably, MPT0G236 significantly inhibited the activities of HDAC1, HDAC2, and HDAC3, Class I HDACs, as well as HDAC6, a Class IIb HDAC, at low nanomolar concentrations. Additionally, it promoted the accumulation of acetyl-α-tubulin and acetyl-histone H3 in HCT-116 and HT-29 cells in a concentration-dependent manner. Furthermore, MPT0G236 treatment induced G2/M cell cycle arrest in CRC cells by initially regulating the levels of cell-cycle-related proteins, such as p-MPM2; specifically reducing p-cdc2 (Y15), cyclin B1, and cdc25C levels; and subsequently inducing apoptosis through the caspase-dependent pathways and PARP activation. Our findings demonstrate that MPT0G236 exhibits significant anticancer activity in human colorectal cancer cells.

S1P signaling, its interactions and cross-talks with other partners and therapeutic importance in colorectal cancer

Sphingosine-1-Phosphate (S1P) plays an important role in normal physiology, inflammation, initiation and progression of cancer. Deregulation of S1P signaling causes aberrant proliferation, affects survival, leads to angiogenesis and metastasis. Sphingolipid rheostat is crucial for cellular homeostasis. Discrepancy in sphingolipid metabolism is linked to cancer and drug insensitivity. Owing to these diverse functions and being a potent mediator of tumor growth, S1P signaling might be a suitable candidate for anti-tumor therapy or combination therapy. In this review, with a focus on colorectal cancer we have summarized the interacting partners of S1P signaling pathway, its therapeutic approaches along with the contribution of S1P signaling to various cancer hallmarks.

A phase 1 trial of the histone deacetylase inhibitor AR-42 in patients with neurofibromatosis type 2-associated tumors and advanced solid malignancies

PURPOSE

Given clinical activity of AR-42, an oral histone deacetylase inhibitor, in hematologic malignancies and preclinical activity in solid tumors, this phase 1 trial investigated the safety and tolerability of AR-42 in patients with advanced solid tumors, including neurofibromatosis type 2-associated meningiomas and schwannomas (NF2). The primary objective was to define the maximum tolerated dose (MTD) and dose-limiting toxicities (DLTs). Secondary objectives included determining pharmacokinetics and clinical activity.

METHODS

This phase I trial was an open-label, single-center, dose-escalation study of single-agent AR-42 in primary central nervous system and advanced solid tumors. The study followed a 3 + 3 design with an expansion cohort at the MTD.

RESULTS

Seventeen patients were enrolled with NF2 (n = 5), urothelial carcinoma (n = 3), breast cancer (n = 2), non-NF2-related meningioma (n = 2), carcinoma of unknown primary (n = 2), small cell lung cancer (n = 1), Sertoli cell carcinoma (n = 1), and uveal melanoma (n = 1). The recommended phase II dose is 60 mg three times weekly, for 3 weeks of a 28-day cycle. DLTs included grade 3 thrombocytopenia and grade 4 psychosis. The most common treatment-related adverse events were cytopenias, fatigue, and nausea. The best response was stable disease in 53% of patients (95% CI 26.6-78.7). Median progression-free survival (PFS) was 3.6 months (95% CI 1.2-9.1). Among evaluable patients with NF2 or meningioma (n = 5), median PFS was 9.1 months (95% CI 1.9-not reached).

CONCLUSION

Single-agent AR-42 is safe and well tolerated. Further studies may consider AR-42 in a larger cohort of patients with NF2 or in combination with other agents in advanced solid tumors.

TRIAL REGISTRATION

NCT01129193, registered 5/24/2010.

Targeting LncRNA EPIC1 to inhibit human colon cancer cell progression

Long non-coding RNA EPIC1 (Lnc-EPIC1) binds MYC protein, which is essential for MYC function and expression of MYC target genes. The current study tested its expression and potential functions in human colon cancer cells. We show that Lnc-EPIC1 expression is elevated in human colon cancer tissues and primary human colon cancer cells. Whereas its expression is relatively low in normal colon tissues and colon epithelial cells. In the primary human colon cancer cells, Lnc-EPIC1 siRNA largely inhibited cancer cell growth, proliferation, migration and invasion. Further, Lnc-EPIC1 silencing induced significant apoptosis activation in colon cancer cells. Conversely, ectopic overexpression of Lnc-EPIC1 augmented colon cancer cell growth, proliferation, migration and invasion. RNA-immunoprecipitation and RNA pull-down results confirmed that Lnc-EPIC1 directly binds MYC protein in colon cancer cells. MYC target proteins, including cyclin A, cyclin D and CDK9, were downregulated with Lnc-EPIC1 silencing, but upregulated after Lnc-EPIC1 overexpression in colon cancer cells. Further Lnc-EPIC1 silencing or overexpression failed to alter functions of MYC-knockout colon cancer cells. Collectively, overexpressed Lnc-EPIC1 is important for the progression of human colon cancer cells.

The therapeutic effect of the BRD4-degrading PROTAC A1874 in human colon cancer cells

A1874 is a novel BRD4-degrading proteolysis targeting chimera (PROTAC). In primary colon cancer cells and established HCT116 cells, A1874 potently inhibited cell viability, proliferation, cell cycle progression, as well as cell migration and invasion. The BRD4-degrading PROTAC was able to induce caspase and apoptosis activation in colon cancer cells. Furthermore, A1874-induced degradation of BRD4 protein and downregulated BRD-dependent genes (c-Myc, Bcl-2, and cyclin D1) in colon cancer cells. Significantly, A1874-induced anti-colon cancer cell activity was more potent than the known BRD4 inhibitors (JQ1, CPI203, and I-BET151). In BRD4-knockout colon cancer cells A1874 remained cytotoxic, indicating the existence of BRD4-independent mechanisms. In addition to BRD4 degradation, A1874 cytotoxicity in colon cancer cells was also associated with p53 protein stabilization and reactive oxygen species production. Importantly, the antioxidant N-acetyl-cysteine and the p53 inhibitor pifithrin-α attenuated A1874-induced cell death and apoptosis in colon cancer cells. In vivo, A1874 oral administration potently inhibited colon cancer xenograft growth in severe combined immuno-deficient mice. BRD4 degradation and p53 protein elevation, as well as apoptosis induction and oxidative stress were detected in A1874-treated colon cancer tissues. Together, A1874 inhibits colon cancer cell growth through both BRD4-dependent and -independent mechanisms.

Dysregulation of histone deacetylases in carcinogenesis and tumor progression: a possible link to apoptosis and autophagy

Dysregulation of the epigenome and constitutional epimutation lead to aberrant expression of the genes, which regulate cancer initiation and progression. Histone deacetylases (HDACs), which are highly conserved in yeast to humans, are known to regulate numerous proteins involved in the transcriptional regulation of chromatin structures, apoptosis, autophagy, and mitophagy. In addition, a non-permissive chromatin conformation is created by HDACs, preventing the transcription of the genes encoding the proteins associated with tumorigenesis. Recently, an expanding perspective has been reported from the clinical trials with HDACis (HDAC inhibitors), which has emerged as a determining target for the study of the detailed mechanisms underlying cancer progression. Therefore, the present review focuses on the comprehensive lucubration of post-translational modifications and the molecular mechanisms through which HDACs alter the ambiguities associated with epigenome, with particular insights into the initiation, progression, and regulation of cancer.

Targeting p38γ to inhibit human colorectal cancer cell progression

Colorectal cancer (CRC) is a common malignancy globally causing significant cancer-related mortality. Recent studies have proposed p38gamma (p38γ) as a novel cyclin-dependent kinase (CDK)-like kinase, promoting tumorigenesis and cancer progression. The current study evaluates p38γ expression and potential role in CRC. In HT-29 cells and primary human colon cancer cells, shRNA-induced p38γ silencing or CRISPR/Cas9-mediated p38γ knockout inhibited cell growth, proliferation, and migration, and induced significant apoptosis. Conversely, ectopic overexpression of p38γ further promoted the growth, proliferation, and migration of HT-29 cells and primary colon cancer cells. Retinoblastoma (Rb) phosphorylation and cyclins (E1/A) expression were decreased by p38γ silencing or KO, but increased with p38γ overexpression. p38γ mRNA and protein levels are significantly upregulated in human colon cancer tissues, when compared to levels in surrounding colon epithelial tissues. These results demonstrate that overexpression of p38γ can promote human CRC cell progression, and identify p38γ as a novel therapeutic target.

Epigenetics and Sphingolipid Metabolism in Health and Disease

Sphingolipids represent one of the major classes of bioactive lipids. Studies of sphingolipids have intensified in the past several years, revealing their roles in nearly all cell biological processes. In addition, epigenetic regulation has gained substantial interest due to its role in controlling gene expression and activity without changing the genetic code. In this review, we first introduce a brief background on sphingolipid biology, highlighting its role in pathophysiology. We then illustrate the concept of epigenetic regulation, focusing on how it affects the metabolism of sphingolipids. We further discuss the roles of bioactive sphingolipids as epigenetic regulators themselves. Overall, a better understanding of the relationship between epigenetics and sphingolipid metabolism may help to improve the development of sphingolipid-targeted therapeutics.

Repurposing of sodium valproate in colon cancer associated with diabetes mellitus: Role of HDAC inhibition

BACKGROUND AND PURPOSE

Diabetic patients are at greater risk for colon cancer. Histone deacetylases (HDACs) serve as common target for both. The key objective of the study was to evaluate the effect of sodium valproate in type 2 diabetes mellitus associated colon cancer.

EXPERIMENTAL APPROACH

High fat diet and streptozotocin were used to induce type 2 diabetes. Following this, after diabetes confirmation, colon cancer was induced using 1,2 dimethylhydrazine (25 mg/kg, s.c.) once weekly from 7th week to 20th weeks. Sodium valproate (200 mg/kg) treatment was given from 20th to 24th week. At the end of 24 weeks, several enzymatic and biochemical parameters, were estimated. MTT, clonogenic and scratch wound healing assay were carried out in HCT-15 cell line.

KEY RESULTS

Hyperglycemia, hyperinsulinemia, increase in cytokines (TNF-α and IL-1β) and carcinoembryonic antigen and presence of proliferating cells was seen in disease control animals which was prevented by sodium valproate treatment. Overexpression of relative HDAC2 mRNA levels was found in diseased control animals, which was reduced by sodium valproate treatment. IC₅₀ of sodium valproate was found to be 3.40 mM and 3.73 mM at 48 h and 72 h respectively on HCT-15 cell line. Sodium valproate also dose dependently prevented colony formation and cell migration.

CONCLUSION AND IMPLICATIONS

Sodium valproate can be considered for repurposing in colon cancer associated with diabetes mellitus.

A phase 1 trial of the HDAC inhibitor AR-42 in patients with multiple myeloma and T- and B-cell lymphomas

Histone deacetylase inhibitors (HDACi) have proven activity in hematologic malignancies, and their FDA approval in multiple myeloma (MM) and T-cell lymphoma highlights the need for further development of this drug class. We investigated AR-42, an oral pan-HDACi, in a first-in-man phase 1 dose escalation clinical trial. Overall, treatment was well tolerated, no DLTs were evident, and the MTD was defined as 40 mg dosed three times weekly for three weeks of a 28-day cycle. One patient each with MM and mantle cell lymphoma demonstrated disease control for 19 and 27 months (ongoing), respectively. Treatment was associated with reduction of serum CD44, a transmembrane glycoprotein associated with steroid and immunomodulatory drug resistance in MM. Our findings indicate that AR-42 is safe and that further investigation of AR-42 in combination regimens for the treatment of patients with lymphoma and MM is warranted.

TRIAL REGISTRATION

http://clinicaltrials.gov/ct2/show/NCT01129193.

Inhibition of SRC-3 enhances sensitivity of human cancer cells to histone deacetylase inhibitors

SRC-3 is widely expressed in multiple tumor types and involved in cancer cell proliferation and apoptosis. Histone deacetylase (HDAC) inhibitors are promising antitumor drugs. However, the poor efficacy of HDAC inhibitors in solid tumors has restricted its further clinical application. Here, we reported the novel finding that depletion of SRC-3 enhanced sensitivity of breast and lung cancer cells to HDAC inhibitors (SAHA and romidepsin). In contrast, overexpression of SRC-3 decreased SAHA-induced cancer cell apoptosis. Furthermore, we found that SRC-3 inhibitor bufalin increased cancer cell apoptosis induced by HDAC inhibitors. The combination of bufalin and SAHA was particular efficient in attenuating AKT activation and reducing Bcl-2 levels. Taken together, these accumulating data might guide development of new breast and lung cancer therapies.

Pre-clinical characterization of 4SC-202, a novel class I HDAC inhibitor, against colorectal cancer cells

Histone deacetylase (HDAC) overactivity in colorectal cancer (CRC) promotes cancer progression. In the current study, we showed that 4SC-202, a novel class I HDAC inhibitor (HDACi), potently inhibited survival and proliferation of primary human colon cancer cells and established CRC lines (HT-29, HCT-116, HT-15, and DLD-1). Yet, the same 4SC-202 treatment was non-cytotoxic to colon epithelial cells where HDAC-1/-2 expressions were extremely low. 4SC-202 provoked apoptosis activation in CRC cells, while caspase inhibitors (z-VAD-CHO and z-DVED-CHO) significantly alleviated 4SC-202-exerted cytotoxicity in CRC cells. Meanwhile, 4SC-202 induced dramatic G2-M arrest in CRC cells. Further studies showed that AKT activation might be an important resistance factor of 4SC-202. 4SC-202-induced cytotoxicity was dramatically potentiated with serum starvation, AKT inhibition (by perifosine or MK-2206), or AKT1-shRNA knockdown in CRC cells. On the other hand, exogenous expression of constitutively active AKT1 (CA-AKT1) decreased the sensitivity by 4SC-202 in HT-29 cells. Notably, 4SC-202, at a low concentration, enhanced oxaliplatin-induced in vitro anti-CRC activity. In vivo, we showed that oral gavage of 4SC-202 inhibited HT-29 xenograft growth in nude mice, and when combined with oxaliplatin, its activity was further strengthened. Together, these pre-clinical results indicate that 4SC-202 may be further investigated as a valuable anti-CRC agent/chemo-adjuvant.