LTP-1, a novel antimitotic agent and Stat3 inhibitor, inhibits human pancreatic carcinomas in vitro and in vivo

Discovery of a 6-Aminobenzo[b]thiophene 1,1-Dioxide Derivative (K2071) with a Signal Transducer and Activator of Transcription 3 Inhibitory, Antimitotic, and Senotherapeutic Activities

6-Nitrobenzo[b]thiophene 1,1-dioxide (Stattic) is a potent signal transducer and activator of the transcription 3 (STAT3) inhibitor developed originally for anticancer therapy. However, Stattic harbors several STAT3 inhibition-independent biological effects. To improve the properties of Stattic, we prepared a series of analogues derived from 6-aminobenzo[b]thiophene 1,1-dioxide, a compound directly obtained from the reduction of Stattic, that includes a methoxybenzylamino derivative (K2071) with optimized physicochemical characteristics, including the ability to cross the blood-brain barrier. Besides inhibiting the interleukin-6-stimulated activity of STAT3 mediated by tyrosine 705 phosphorylation, K2071 also showed cytotoxicity against a set of human glioblastoma-derived cell lines. In contrast to the core compound, a part of K2071 cytotoxicity reflected a STAT3 inhibition-independent block of mitotic progression in the prophase, affecting mitotic spindle formation, indicating that K2071 also acts as a mitotic poison. Compared to Stattic, K2071 was significantly less thiol-reactive. In addition, K2071 affected cell migration, suppressed cell proliferation in tumor spheroids, exerted cytotoxicity for glioblastoma temozolomide-induced senescent cells, and inhibited the secretion of the proinflammatory cytokine monocyte chemoattractant protein 1 (MCP-1) in senescent cells. Importantly, K2071 was well tolerated in mice, lacking manifestations of acute toxicity. The structure-activity relationship analysis of the K2071 molecule revealed the necessity of the para-substituted methoxyphenyl motif for antimitotic but not overall cytotoxic activity of its derivatives. Altogether, these results indicate that compound K2071 is a novel Stattic-derived STAT3 inhibitor and a mitotic poison with anticancer and senotherapeutic properties that is effective on glioblastoma cells and may be further developed as an agent for glioblastoma therapy.

Inhibition of STAT3 by 2-Methoxyestradiol suppresses M2 polarization and protumoral functions of macrophages in breast cancer

BACKGROUND

Breast cancer metastasis remains the leading cause of cancer-related deaths in women worldwide. Infiltration of tumor-associated macrophages (TAMs) in the tumor stroma is known to be correlated with reduced overall survival. The inhibitors of TAMs are sought after for reprogramming the tumor microenvironment. Signal transducer and activator of transcription 3 (STAT3) is well known to contribute in pro-tumoral properties of TAMs. 2-Methoxyestradiol (2ME2), a potent anticancer and antiangiogenic agent, has been in clinical trials for treatment of breast cancer. Here, we investigated the potential of 2ME2 in modulating the pro-tumoral effects of TAMs in breast cancer.

METHODS

THP-1-derived macrophages were polarized to macrophages with or without 2ME2. The effect of 2ME2 on macrophage surface markers and anti-inflammatory genes was determined by Western blotting, flow cytometry, immunofluorescence, qRT‒PCR. The concentration of cytokines secreted by cells was monitored by ELISA. The effect of M2 macrophages on malignant properties of breast cancer cells was determined using colony formation, wound healing, transwell, and gelatin zymography assays. An orthotopic model of breast cancer was used to determine the effect of 2ME2 on macrophage polarization and metastasis in vivo.

RESULTS

First, our study found that polarization of monocytes to alternatively activated M2 macrophages is associated with the reorganization of the microtubule cytoskeleton. At lower concentrations, 2ME2 treatment depolymerized microtubules and reduced the expression of CD206 and CD163, suggesting that it inhibits the polarization of macrophages to M2 phenotype. However, the M1 polarization was not significantly affected at these concentrations. Importantly, 2ME2 inhibited the expression of several anti-inflammatory cytokines and growth factors, including CCL18, TGF-β, IL-10, FNT, arginase, CXCL12, MMP9, and VEGF-A, and hindered the metastasis-promoting effects of M2 macrophages. Concurrently, 2ME2 treatment reduced the expression of CD163 in tumors and inhibited lung metastasis in the orthotopic breast cancer model. Mechanistically, 2ME2 treatment reduced the phosphorylation and nuclear translocation of STAT3, an effect which was abrogated by colivelin.

CONCLUSIONS

Our study presents novel findings on mechanism of 2ME2 from the perspective of its effects on the polarization of the TAMs via the STAT3 signaling in breast cancer. Altogether, the data supports further clinical investigation of 2ME2 and its derivatives as therapeutic agents to modulate the tumor microenvironment and immune response in breast carcinoma.

Characterization of a novel bispecific antibody targeting tissue factor-positive tumors with T cell engagement

T cell engaging bispecific antibody (TCB) is an effective immunotherapy for cancer treatment. Through co-targeting CD3 and tumor-associated antigen (TAA), TCB can redirect CD3⁺ T cells to eliminate tumor cells regardless of the specificity of T cell receptor. Tissue factor (TF) is a TAA that involved in tumor progression. Here, we designed and characterized a novel TCB targeting TF (TF-TCB) for the treatment of TF-positive tumors. In vitro, robust T cell activation, tumor cell lysis and T cell proliferation were induced by TF-TCB. The tumor cell lysis activity was dependent upon both CD3 and TF binding moieties of the TF-TCB, and was related to TF expression level of tumor cells. In vivo, in both tumor cell/human peripheral blood mononuclear cells (PBMC) co-grafting model and established tumor models with poor T cell infiltration, tumor growth was strongly inhibited by TF-TCB. T cell infiltration into tumors was induced during the treatment. Furthermore, efficacy of TF-TCB was further improved by combination with immune checkpoint inhibitors. For the first time, our results validated the feasibility of using TF as a target for TCB and highlighted the potential for TF-TCB to demonstrate efficacy in solid tumor treatment.

Immune checkpoint inhibition for pancreatic ductal adenocarcinoma: limitations and prospects: a systematic review

Pancreatic cancer is an extremely malignant tumor with the lowest 5-year survival rate among all tumors. Pancreatic ductal adenocarcinoma (PDAC), as the most common pathological subtype of pancreatic cancer, usually has poor therapeutic results. Immune checkpoint inhibitors (ICIs) can relieve failure of the tumor-killing effect of immune effector cells caused by immune checkpoints. Therefore, they have been used as a novel treatment for many solid tumors. However, PDAC is not sensitive to monotherapy with ICIs, which might be related to the inhibitory immune microenvironment of pancreatic cancer. Therefore, the way to improve the microenvironment has raised a heated discussion in recent years. Here, we elaborate on the relationship between different immune cellular components in this environment, list some current preclinical or clinical attempts to enhance the efficacy of ICIs by targeting the inhibitory tumor microenvironment of PDAC or in combination with other therapies. Such information offers a better understanding of the sophisticated tumor-microenvironment interactions, also providing insights on therapeutic guidance of PDAC targeting. Video Abstract.

Therapeutic targeting of STAT3 pathways in pancreatic adenocarcinoma: A systematic review of clinical and preclinical literature

BACKGROUND/OBJECTIVES

Pancreatic ductal adenocarcinoma is a highly lethal disease with increasing incidence. Due to high resistance, chemo/radiotherapy has limited success in pancreatic cancer and only marginally prolongs patient survival. Therefore, novel biomarkers and therapeutic targets are needed. In the present review, we performed a comprehensive summary of therapeutic approaches targeting the GP130/JAK/STAT3 pathway.

METHODS

We systematically reviewed the PubMed and Embase databases for preclinical and clinical studies, from inception to October 4, 2020, on drugs targeting the GP130/JAK/STAT3 pathway. Bias assessments and qualitative analyses were performed.

RESULTS

Twenty-five preclinical and nine clinical trials were included in the review. All preclinical studies reported a favorable outcome in terms of pancreatic ductal adenocarcinoma progression. Futhermore, drugs targeting the GP130/JAK/STAT3 pathway were shown to be efficient chemosensitizers. However, high publication bias was assumed. In the clinical setting, bazedoxifene and itacitinib improved patient outcomes.

CONCLUSION

Preclinical studies strongly suggest significant efficacy of drugs targeting GP130/JAK/STAT3 in the treatment of pancreatic ductal adenocarcinoma and that these molecules are effective chemosensitizers. Though only a few trials have shown the efficacy in a clinical setting, the STAT3 pathway remains a promising drug target for future treatment of pancreatic ductal adenocarcinoma and may help overcome chemotherapy resistance.

Targeting the tumor microenvironment in pancreatic ductal adenocarcinoma

Introduction: The dismally slow improvement in patient survival over the years for pancreatic cancer patients is mainly due to two factors: the late diagnosis, at which point the disease is spread to distant organs; and the fact that tumor cells are surrounded by a dense, highly immunosuppressive microenvironment. The tumor microenvironment not only shields pancreatic cancer cells from chemotherapy but also leaves it unsusceptible to various immunotherapeutic strategies that have been proven successful in other types of cancer. Areas covered: This review highlights the main components of the pancreatic tumor microenvironment, how they cross-talk with each other to generate stroma and promote tumor growth. Additionally, we discuss the most promising treatment targets in the microenvironment whose modulation can be robustly tested in combination with standard of care chemotherapy. Currently, active clinical trials for pancreatic cancer involving components of the microenvironment are also listed. Expert opinion: Although immunotherapeutic approaches involving checkpoint inhibition are being pursued enthusiastically, there is still more work to be done with several other emerging immune targets that could provide therapeutic benefit.

Combination treatment strategy for pancreatic cancer involving the novel HDAC inhibitor MPT0E028 with a MEK inhibitor beyond K-Ras status

BACKGROUND

Oncogenic K-Ras signaling highly relies on the canonical Ras/MEK/ERK pathway to contribute to pancreatic cancer progression. However, numerous efforts of MEK inhibitors have failed to provide an optimal antitumor effect for pancreatic cancer in practice. The aim of the present work was to develop a more efficacious therapeutic intervention for MEK inhibitors through combination with histone deacetylase (HDAC) inhibitor MPT0E028.

METHODS

The effects of combined therapy on cell viability, apoptosis, protein, and RNA expressions were determined by MTT assay, flow cytometry, western blotting, and quantitative PCR analysis. The AsPC-1 xenograft was used to assess antitumor effects in vivo.

RESULTS

The co-administration of MPT0E028 and MEK inhibitor yielded synergistic effects on cell viability suppression both in K-Ras mutated and wild-type pancreatic cancer cells and also markedly triggered cell apoptosis. Surprisingly, ERK and epidermal growth factor receptor (EGFR) were activated by the long-term and low-concentration treatment of MPT0E028 or another HDAC inhibitor alone. Whereas, the pharmacological attenuation of ERK signaling dramatically abolished the MPTE028-induced p-ERK and EGFR expression. Overexpression of HDAC4, HDAC6, and MEK, respectively, reversed the cell death induced by the combined treatment. Finally, the combined treatment decreased the tumor volume in an AsPC-1 xenograft model compared to each individual treatment alone.

CONCLUSIONS

The synergistic anti-survival effect of the combination was suggested to occur via compensation of the MEK inhibitor for activated ERK. Our results indicate that this combination strategy could benefit patients with pancreatic cancer beyond K-Ras status.

Antitubulin sulfonamides: The successful combination of an established drug class and a multifaceted target

Tubulin, the microtubules and their dynamic behavior are amongst the most successful antitumor, antifungal, antiparasitic, and herbicidal drug targets. Sulfonamides are exemplary drugs with applications in the clinic, in veterinary and in the agrochemical industry. This review summarizes the actual state and recent progress of both fields looking from the double point of view of the target and its drugs, with special focus onto the structural aspects. The article starts with a brief description of tubulin structure and its dynamic assembly and disassembly into microtubules and other polymers. Posttranslational modifications and the many cellular means of regulating and modulating tubulin's biology are briefly presented in the tubulin code. Next, the structurally characterized drug binding sites, their occupying drugs and the effects they induce are described, emphasizing on the structural requirements for high potency, selectivity, and low toxicity. The second part starts with a summary of the favorable and highly tunable combination of physical-chemical and biological properties that render sulfonamides a prototypical example of privileged scaffolds with representatives in many therapeutic areas. A complete description of tubulin-binding sulfonamides is provided, covering the different species and drug sites. Some of the antimitotic sulfonamides have met with very successful applications and others less so, thus illustrating the advances, limitations, and future perspectives of the field. All of them combine in a mechanism of action and a clinical outcome that conform efficient drugs.

Myeloid-derived suppressor cells and their role in pancreatic cancer

Pancreatic cancer is a devastating disease and ranks as the third most common cause of cancer-related death. Like many cancers, there has been increased interest in the role of the immune system in the progression and development of pancreatic cancer. In particular, immunosuppression within the tumor microenvironment (TME) is thought to impair the host's antitumor response. In this article, we review myeloid-derived suppressor cells and their contribution to this immunosuppression within the pancreatic TME.