Metronomic small molecule inhibitor of Bcl-2 (TW-37) is antiangiogenic and potentiates the antitumor effect of ionizing radiation

Small Molecule Targeting Immune Cells: A Novel Approach for Cancer Treatment

Conventional and cancer immunotherapies encompass diverse strategies to address various cancer types and stages. However, combining these approaches often encounters limitations such as non-specific targeting, resistance development, and high toxicity, leading to suboptimal outcomes in many cancers. The tumor microenvironment (TME) is orchestrated by intricate interactions between immune and non-immune cells dictating tumor progression. An innovative avenue in cancer therapy involves leveraging small molecules to influence a spectrum of resistant cell populations within the TME. Recent discoveries have unveiled a phenotypically diverse cohort of innate-like T (ILT) cells and tumor hybrid cells (HCs) exhibiting novel characteristics, including augmented proliferation, migration, resistance to exhaustion, evasion of immunosurveillance, reduced apoptosis, drug resistance, and heightened metastasis frequency. Leveraging small-molecule immunomodulators to target these immune players presents an exciting frontier in developing novel tumor immunotherapies. Moreover, combining small molecule modulators with immunotherapy can synergistically enhance the inhibitory impact on tumor progression by empowering the immune system to meticulously fine-tune responses within the TME, bolstering its capacity to recognize and eliminate cancer cells. This review outlines strategies involving small molecules that modify immune cells within the TME, potentially revolutionizing therapeutic interventions and enhancing the anti-tumor response.

GADRP: graph convolutional networks and autoencoders for cancer drug response prediction

Drug response prediction in cancer cell lines is of great significance in personalized medicine. In this study, we propose GADRP, a cancer drug response prediction model based on graph convolutional networks (GCNs) and autoencoders (AEs). We first use a stacked deep AE to extract low-dimensional representations from cell line features, and then construct a sparse drug cell line pair (DCP) network incorporating drug, cell line, and DCP similarity information. Later, initial residual and layer attention-based GCN (ILGCN) that can alleviate over-smoothing problem is utilized to learn DCP features. And finally, fully connected network is employed to make prediction. Benchmarking results demonstrate that GADRP can significantly improve prediction performance on all metrics compared with baselines on five datasets. Particularly, experiments of predictions of unknown DCP responses, drug-cancer tissue associations， and drug-pathway associations illustrate the predictive power of GADRP. All results highlight the effectiveness of GADRP in predicting drug responses, and its potential value in guiding anti-cancer drug selection.

Engineered Oncolytic Adenoviruses: An Emerging Approach for Cancer Therapy

Cancer is among the major leading causes of mortality globally, and chemotherapy is currently one of the most effective cancer therapies. Unfortunately, chemotherapy is invariably accompanied by dose-dependent cytotoxic side effects. Recently, genetically engineered adenoviruses emerged as an alternative gene therapy approach targeting cancers. This review focuses on the characteristics of genetically modified adenovirus and oncology clinical studies using adenovirus-mediated gene therapy strategies. In addition, modulation of the tumor biology and the tumor microenvironment as well as the immunological responses associated with adenovirus-mediate cancer therapy are discussed.

Cutting the umbilical cord: Cancer stem cell-targeted therapeutics

Cancer Stem Cells (CSCs) are a notoriously quiescent subpopulation of cells within heterogeneous tumors exhibiting self-renewal, differentiation and drug-resistant capabilities leading to tumor relapse. Heterogeneous cell populations in tumor microenvironment develop an elaborate network of signalling and factors supporting the CSC population within a niche. Identification of specific biomarkers for CSCs facilitates their isolation. CSCs demonstrate abilities that bypass immune surveillance, exhibit resistance to therapy, and induce cancer recurrence while promoting altered metabolism of the bulk tumor, thereby encouraging metastasis. The fight against cancer is prone to relapse without discussing the issue of CSCs, making it imperative for encapsulation of current studies. In this review, we provide extensive knowledge of recent therapeutics developed that target CSCs via multiple signalling cascades, altered metabolism and the tumor microenvironment. Thorough understanding of the functioning of CSCs, their interaction with different cells in the tumor microenvironment as well as current gaps in knowledge are addressed. We present possible strategies to disrupt the cellular and molecular interplay within the tumor microenvironment and make it less conducive for CSCs, which may aid in their eradication with subsequently better treatment outcomes. In conclusion, we discuss a brief yet functional idea of emerging concepts in CSC biology to develop efficient therapeutics acting on cancer recurrence and metastasis.

Systematic Review of Gossypol/AT-101 in Cancer Clinical Trials

The potential of gossypol and of its R-(−)-enantiomer (R-(−)-gossypol acetic acid, AT-101), has been evaluated for treatment of cancer as an independent agent and in combination with standard chemo-radiation-therapies, respectively. This review assesses the evidence for safety and clinical effectiveness of oral gossypol/AT-101 in treating various types of cancer. The databases PubMed, MEDLINE, Cochrane, and ClinicalTrials.gov were examined. Phase I and II trials as well as single arm and randomized trials were included in this review. Results were screened to determine if they met inclusion criteria and then summarized using a narrative approach. A total of 17 trials involving 759 patients met the inclusion criteria. Overall, orally applied gossypol/AT-101 at low doses (30 mg daily or lower) was determined as well tolerable either as monotherapy or in combination with chemo-radiation. Adverse events should be strictly monitored and were successfully managed by dose-reduction or treating symptoms. There are four randomized trials, two performed in patients with advanced non-small cell lung cancer, one in subjects with head and neck cancer, and one in patients with metastatic castration-resistant prostate cancer. Thereby, standard chemotherapy (either docetaxel (two trials) or docetaxel plus cisplatin or docetaxel plus prednisone) was tested with and without AT-101. Within these trials, a potential benefit was observed in high-risk patients or in some patients with prolongation in progression-free survival or in overall survival. Strikingly, the most recent clinical trial combined low dose AT-101 with docetaxel, fluorouracil, and radiation, achieving complete responses in 11 of 13 patients with gastroesophageal carcinoma (median duration of 12 months) and a median progression-free survival of 52 months. The promising results shown in subsets of patients supports the need of further specification of AT-101 sensitive cancers as well as for the establishment of effective AT-101-based therapy. In addition, the lowest recommended dose of gossypol and its precise toxicity profile need to be confirmed in further studies. Randomized placebo-controlled trials should be performed to validate these data in large cohorts.

Targeting Bcl-2 for cancer therapy

Apoptosis deficiency is one of the most important features observed in neoplastic diseases. The Bcl-2 family is composed of a subset of proteins that act as decisive apoptosis regulators. Research and clinical studies have both demonstrated that the hyperactivation of Bcl-2-related anti-apoptotic effects correlates with cancer occurrence, progression and prognosis, also having a role in facilitating the radio- and chemoresistance of various malignancies. Therefore, targeting Bcl-2 inactivation has provided some compelling therapeutic advantages by enhancing apoptotic sensitivity or reversing drug resistance. Therefore, this pharmacological route turned into one of the most promising routes for cancer treatment. This review discusses some of the well-defined and emerging roles of Bcl-2 as well as its potential clinical value in cancer therapeutics.

Targeting Tumor Microenvironment by Small-Molecule Inhibitors

The tumor microenvironment (TME) is a hypoxic, acidic, and immune/inflammatory cell–enriched milieu that plays crucial roles in tumor development, growth, progression, and therapy resistance. Targeting TME is an attractive strategy for the treatment of solid tumors. Conventional cancer chemotherapies are mostly designed to directly kill cancer cells, and the effectiveness is always compromised by their penetration and accessibility to cancer cells. Small-molecule inhibitors, which exhibit good penetration and accessibility, are widely studied, and many of them have been successfully applied in clinics for cancer treatment. As TME is more penetrable and accessible than tumor cells, a lot of efforts have recently been made to generate small-molecule inhibitors that specifically target TME or the components of TME or develop special drug-delivery systems that release the cytotoxic drugs specifically in TME. In this review, we briefly summarize the recent advances of small-molecule inhibitors that target TME for the tumor treatment.

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Tumor microenvironment (TME) is an indispensable part of tumor and is an important therapeutic target.

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TME is more penetrable and accessible than tumor cell area.

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Small-molecule inhibitors that target TME are very promising.

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The target efficiency can be improved by specific deliver and release systems.

The small molecule Bcl-2/Mcl-1 inhibitor TW-37 shows single-agent cytotoxicity in neuroblastoma cell lines

Background

High-risk neuroblastoma with N-Myc amplification remains a therapeutic challenge in paediatric oncology. Antagonism of pro-death Bcl-2 homology (BH) proteins to pro-survival BH members such as Mcl-1 and Bcl-2 has become a treatment approach, but previous studies suggest that a combined inhibition of Bcl-2 and Mcl-1 is necessary. TW-37 inhibits Mcl-1 and Bcl-2 with almost the same affinity. However, single-agent cytotoxicity of TW-37 in neuroblastoma cell lines has not been investigated.

Methods

Cell viability, apoptosis, proliferation and changes in growth properties were determined in SKNAS, IMR-5, SY5Y and Kelly cells after treatment with TW-37. After transfection with Mcl-1 or Bcl-2 siRNA, apoptosis and proliferation were investigated in Kelly cells. Mice with Kelly cell line xenografts were treated with TW-37 and tumor growth, survival and apoptosis were determined.

Results

Cell lines with N-Myc amplification were more sensitive to TW-37 treatment, IC50 values for IMR-5 and Kelly cells being 0.28 μM and 0.22 μM, compared to SY5Y cells and SKNAS cells (IC50 0.96 μM and 0.83 μM). Treatment with TW-37 resulted in increased apoptosis and reduced proliferation rates, especially in IMR5 and Kelly cells. Bcl-2 as well as Mcl-1 knockdown induced apoptosis in Kelly cells. TW-37 led to a decrease in tumor growth and a favorable survival (p = 0.0379) in a Kelly neuroblastoma xenografts mouse model.

Conclusion

TW-37 has strong single-agent cytotoxicity in vitro and in vivo. Therefore, combined inhibition of Bcl-2/Mcl-1 by TW-37 in N-Myc amplified neuroblastoma may represent an interesting therapeutic strategy.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5439-1) contains supplementary material, which is available to authorized users.

Effect of TW37 on the growth of H1975 EGFR‑TKI‑resistant lung cancer cells and its underlying mechanisms

Previous studies have suggested that the B‑cell lymphoma 2 (Bcl‑2) inhibitor, TW37, may induce apoptosis of the non‑small cell lung cancer cell line, H1975/epidermal growth factor receptor‑tyrosine kinase inhibitor (EGFR‑TKI), which exhibits secondary resistance to EGFR‑TKI. However, the effects of TW37 on H1975/EGFR‑TKI cells remain unclear. The aim of the present study was to investigate the effects of TW37 on the growth of H1975/EGFR‑TKI cells and explore the underlying mechanisms. An in vitro study was performed, whereby H1975/EGFR‑TKI cells were treated with serially increasing concentrations of TW37. MTT, flow cytometry, migration and transwell invasion assays were preformed to investigate the proliferation, apoptosis, migration and invasion of H1975/EGFR‑TKI cells, respectively. In addition, reverse transcription‑polymerase chain reaction and western blot analyses were performed to detect the mRNA and protein expression levels of apoptosis‑associated factors, respectively. An enzyme‑linked immunosorbent assay was performed to detect phosphatidylinositol [3,4,5] tris‑phosphate (PIP3) expression. The results suggested that the mRNA and protein expression levels of Bcl‑2 were significantly decreased in TW37‑treated cells when compared with the untreated control group. Following treatment with TW37, the proliferation, migration and invasion ability of H1975/EGFR‑TKI cells decreased in a dose‑dependent manner, while the percentage of apoptotic cells increased. In addition, the results demonstrated that TW37 reduced the expression of PIP3 and the phosphorylation of AKT serine/threonine kinase 1 (AKT) in H1975/EGFR‑TKI cells in a dose‑dependent manner. In conclusion, TW37 inhibited H1975/EGFR‑TKI cell growth and induced cell apoptosis potentially via suppression of AKT signaling pathway activation.

Small molecule inhibitor TW-37 is tolerable and synergistic with chemotherapy in nasopharyngeal carcinoma

Chemotherapy is a crucial adjuvant therapy of advanced nasopharyngeal carcinoma (NPC). However, enhancing sensitivity and tolerance of chemotherapeutics in NPC treatment have been challenging. Both Bcl-2 and Mcl-1, 2 pro-survival proteins of Bcl-2 family, play essential roles on the chemotherapy tolerance of numerous cancers. In the present study, we explored the influences of TW-37, a small molecule inhibitor of Bcl-2 and Mcl-1, on the efficiency of chemotherapy for NPC. Oncomine cancer database shows that NPC tissues have higher expression of Bcl-2 and Mcl-1 than those of normal nasopharyngeal epithelial (NPE) tissues. And our results reveal that chemotherapeutics, Cisplatin (CDDP) and 5-Fluoracil (5-FU), result in the greater decrease of protein level of Bcl-2 and Mcl-1 in NPC cells than those in NPE cells. TW-37 does not have significant impact on the chemotherapeutics-treated NPE cell viability at a dosage that efficiently reduces chemotherapeutics-treated NPC cell viability. Moreover, impacts of TW-37 on the cell viability of chemotherapeutics-treated NPC cells are dependent on the expression of Bcl-2 and Mcl-1 in NPC cells. Further explorations suggest that TW-37 prominently promotes apoptosis in NPC cells under chemotherapeutics treatments but not in NPE cells. Meanwhile, TW-37 also remarkably reduces colony formation ability of chemotherapeutics-treated NPC cells. Importantly, in vivo models, TW-37 observably increases chemosensitivity of NPC tumors but has not markedly influence on the normal tissues in mice. In conclusion, our results point to TW-37 as a promising ancillary drug for the chemotherapy of NPC.

Head and neck cancer: metronomic chemotherapy

In the era of personalized medicine, head and neck squamous cell carcinoma (HNSCC) represents a critical oncologic topic. Conventional chemotherapy regimens consist of drugs administration in cycles near or at the maximum tolerated dose (MDT), followed by a long drug-free period to permit the patient to recover from acute toxicities. Despite this strategy is successful in controlling the cancer process at the beginning, a significant number of HNSCC patients tend to recurred or progress, especially those patients with locally advanced or metastatic disease. The repertoire of drugs directed against tumor cells has greatly increased and metronomic chemotherapy (MC) could be an effective treatment option.

It is the purpose of this article to review the concept of MC and describe its potential use in HNSCC. We provide an update of ongoing progress and current challenges related to this issue.

Anti-cancer drug discovery and development: Bcl-2 family small molecule inhibitors

Deregulated apoptosis is a hallmark of cancer, and the B-cell lymphoma-2 (Bcl-2) family of proteins is pivotal to mediating the intrinsic pathway of this process. Recent advances have yielded both pan-Bcl-2 small molecule inhibitors (SMIs) that inhibit both the Bcl-2 and the Mcl-1 arm of the Bcl-2 family anti-apoptotic proteins, as well as selective SMIs to differentially target the two arms. Of these SMIs, ABT-263 (navitoclax), AT-101 [(-)-gossypol], and obatoclax (GX15-070) are currently in clinical trials for multiple cancers. While pan-Bcl-2 inhibitors such as AT-101 and obatoclax can be more toxic for inhibiting all members of the anti-apoptotic Bcl-2 family of proteins, resistance can quickly develop for ABT-263, a selective Bcl-2 inhibitor. In this article, we discuss the current status of Bcl-2 family SMIs in preclinical and clinical development. As Mcl-1 upregulation is a major mechanism of ABT-263 resistance, Mcl-1-specific inhibitors are expected to be efficacious both in combination/sequential treatments and as a single agent against cancers resistant to ABT-263. 

RAIN-Droplet: a novel 3D in vitro angiogenesis model

Angiogenesis is fundamentally required for the initialization, development and metastatic spread of cancer. A rapidly expanding number of new experimental, chemical modulators of endothelial cell function have been described for the therapeutic inhibition of angiogenesis in cancer. Despite this expansion, there has been very limited parallel growth of in vitro angiogenesis models or experimental tools. Here we present the Responsive Angiogenic Implanted Network (RAIN)-Droplet model and novel angiogenesis assay using an endothelial cell culture model of microvascular endothelial cells encapsulated in a spontaneously self-assembling, toroidal hydrogel droplet uniquely yielding discrete, pre-formed, angiogenic networks that may be embedded in 3D matrices. On embedding, radial growth of capillary-like sprouts and cell invasion was observed. The sprouts formed not only as outgrowths from endothelial cells on the surface of the droplets, but also, uniquely, from the pre-formed network structures within the droplet. We demonstrate proof of principle for the utility of the model showing significant inhibition of sprout formation (P<0.001) in the presence of bevacizumab, an anti-angiogenic antibody. Using the RAIN-Droplet assay, we also demonstrate a novel dose-dependent pro-angiogenic function for the characteristically anti-angiogenic multi-kinase inhibitor sorafenib. Exposure of endothelial cells in 3D culture to low, non-lethal doses (<1 μM) of sorafenib after initiation of sprouting resulted in the formation of significantly (P<0.05) more endothelial sprouts compared with controls over a 48-h period. Higher doses of sorafenib (5 μM) resulted in a significant (P<0.05) reduction of sprouting over the same time period. The RAIN-Droplet model is a highly versatile and simply constructed 3D focal sprouting approach well suited for the study of vascular morphogenesis and for preclinical testing of drugs. Furthermore, the RAIN-Droplet model has facilitated the discovery of a novel pro-angiogenic capacity for sorafenib, which may impact the clinical application and dosing regimen of that drug.

Metronomic dosing of BH3 mimetic small molecule yields robust antiangiogenic and antitumor effects

Bcl-2 is an antiapoptotic protein that has also been found to function as a proangiogenic signaling molecule. Improvements in antiangiogenic therapy can be engendered by metronomic dosing. Thus, we hypothesized that BH3-mimetic drugs that antagonize Bcl-2 family proteins may exert a greater efficacy when dosed metronomically. To examine this hypothesis, we employed AT101, an orally available and well-tolerated BH3-mimetic drug that has been established as effective. In a mouse xenograft model of human squamous cell carcinomas (SCC) that includes a humanized vasculature, we explored the effects of docetaxel in combination with either daily (metronomic) or weekly (bolus) doses of AT101. In addition, we explored the effect of single or combination therapy on angiogenesis and survival of endothelial or SCC cells in vitro. Metronomic AT101 therapy increased mouse survival, decreased tumor mitotic index, and decreased tumor microvessel density, compared with bolus therapy. Therapeutic potentiation was achieved by similar overall drug exposure and without altering systemic toxicities. Combinations of AT101 and docetaxel produced additive toxicity in both endothelial and SCC tumor cells. Notably, subapoptotic concentrations of AT101 potently inhibited the angiogenic potential of endothelial cells. Taken together, our findings unveil the efficacious benefits that can be achieved by metronomic delivery of BH3-mimetic drugs, in particular suggesting that SCC patients with might benefit from low-dose continuous administration of these drugs.

(-)-Gossypol suppresses the growth of human prostate cancer xenografts via modulating VEGF signaling-mediated angiogenesis

(-)-Gossypol, a natural BH3-mimetic and small-molecule Bcl-2 inhibitor, shows promise in ongoing phase II clinical trials for human cancers. However, whether (-)-gossypol plays functional roles in tumor angiogenesis has not been directly elucidated yet. In this study, we showed that (-)-gossypol dose dependently inhibited the expression of VEGF, Bcl-2, and Bcl-xL in human prostate cancer cells (PC-3 and DU 145) and primary cultured human umbilical vascular endothelial cells (HUVEC) in vitro. Notably, the growth of human prostate tumor PC-3 xenografts in mice was significantly suppressed by (-)-gossypol at a dosage of 15 mg/kg/d. This inhibitory action of (-)-gossypol in vivo was largely dependent on suppression of angiogenesis in the solid tumors, where VEGF expression and microvessel density were remarkably decreased. Furthermore, (-)-gossypol inhibited VEGF-induced chemotactic motility and tubulogenesis in HUVECs and human microvascular endothelial cells and suppressed microvessel sprouting from rat aortic rings ex vivo. When examined for the mechanism, we found that (-)-gossypol blocked the activation of VEGF receptor 2 kinase with the half maximal inhibitory concentration of 2.38 μmol/L in endothelial cells. Consequently, the phosphorylation of key intracellular proangiogenic kinases induced by VEGF was all suppressed by the treatment, such as Src family kinase, focal adhesion kinase, extracellular signal-related kinase, and AKT kinase. Taken together, the present study shows that (-)-gossypol potently inhibits human prostate tumor growth through modulating VEGF signaling pathway, which further validates its great potential in clinical practice.

Small-molecule inhibitors reveal a new function for Bcl-2 as a proangiogenic signaling molecule

Cancer has a complex etiology and displays a wide range of cellular escape pathways that allow it to circumvent treatment. Signaling molecules functionally downstream of the circumvented pathways, and particularly at checkpoints where several of these pathways intersect, provide valuable targets for the development of novel anti-cancer drugs. Bcl-2, a pro-survival signaling molecule, is one such protein. This review examines the efficacy, potency, and function of several small molecule inhibitor drugs targeted to the Bcl-2 family of proteins. The review focuses on the compounds with most available data within the literature and discusses both the anti-cancer and the recently unveiled anti-angiogenic potential of this new class of drugs.