HDAC inhibition synergizes with ALK inhibitors to overcome resistance in a novel ALK mutated lung adenocarcinoma model

Advances of dual inhibitors based on ALK for the treatment of cancer

Anaplastic lymphoma kinase (ALK), which encodes a highly conserved receptor tyrosine kinase (RTK), is important for the development and progression of many tumors, especially non-small cell lung cancer (NSCLC). Currently, third-generation ALK inhibitors are used to treat ALK-mutant NSCLC, but the rapid emergence of resistance during treatment greatly limits their efficacy in clinic. In comparison to single-target inhibitors, ALK dual inhibitors offer the benefits of reducing the emergence of drug resistance, improving treatment efficacy, and optimizing pharmacokinetic features due to the synergistic function of ALK and other associated targets involved in tumor progression. Therefore, we outline the development of ALK dual inhibitors, highlight their design approaches and structure-activity relationship (SAR), and offer insights into new challenges and potential future directions in this area.

ALK-based dual inhibitors: Focus on recent development for non-small cell lung cancer therapy

As a prevalent oncogenic driver gene in non-small cell lung cancer (NSCLC), ALK represents a crucial and efficacious therapeutic target. To date, seven ALK inhibitors have been approved for ALK fusion-positive NSCLC, with several others undergoing clinical trials. These therapies demonstrate significant efficacy in ALK fusion-positive NSCLC patients. However, acquired resistance mechanisms, including ALK kinase domain mutations, ALK gene amplification, and bypass pathway activation, significantly compromise the efficacy of targeted therapy in ALK fusion-positive NSCLC. Therefore, the discovery of novel ALK inhibitors and the development of related treatment strategies remain critical. Compared to the combination therapy strategy based on ALK inhibitors, dual-target inhibitors (targeting two distinct pathways within a single molecule) may reduce systemic toxicity and mitigate resistance mechanisms in cancer treatment. Notably, recent years have witnessed remarkable progress in dual-target ALK inhibitor development for NSCLC. Consequently, this review aims to summarize the advancements achieved through dual ALK-based inhibitors in NSCLC therapy, analyze their rational design and structure-activity relationships, and provide perspectives for overcoming resistance through next-generation inhibitors and innovative therapeutic approaches.

LDHB silencing enhances the effects of radiotherapy by impairing nucleotide metabolism and promoting persistent DNA damage

Lung cancer is the leading cause of cancer-related deaths globally, with radiotherapy as a key treatment modality for inoperable cases. Lactate, once considered a by-product of anaerobic cellular metabolism, is now considered critical for cancer progression. Lactate dehydrogenase B (LDHB) converts lactate to pyruvate and supports mitochondrial metabolism. In this study, a re-analysis of our previous transcriptomic data revealed that LDHB silencing in the NSCLC cell lines A549 and H358 dysregulated 1789 genes, including gene sets associated with cell cycle and DNA repair pathways. LDHB silencing increased H2AX phosphorylation, a surrogate marker of DNA damage, and induced cell cycle arrest at the G1/S or G2/M checkpoint depending on the p53 status. Long-term LDHB silencing sensitized A549 cells to radiotherapy, resulting in increased DNA damage and genomic instability as evidenced by increased H2AX phosphorylation levels and micronuclei accumulation, respectively. The combination of LDHB silencing and radiotherapy increased protein levels of the senescence marker p21, accompanied by increased phosphorylation of Chk2, suggesting persistent DNA damage. Metabolomics analysis revealed that LDHB silencing decreased nucleotide metabolism, particularly purine and pyrimidine biosynthesis, in tumor xenografts. Nucleotide supplementation partially attenuated DNA damage caused by combined LDHB silencing and radiotherapy. These findings suggest that LDHB supports metabolic homeostasis and DNA damage repair in NSCLC, while its silencing enhances the effects of radiotherapy by impairing nucleotide metabolism and promoting persistent DNA damage.

Ubiquinol-mediated suppression of mitochondria-associated ferroptosis is a targetable function of lactate dehydrogenase B in cancer

Lactate dehydrogenase B (LDHB) fuels oxidative cancer cell metabolism by converting lactate to pyruvate. This study uncovers LDHB's role in countering mitochondria-associated ferroptosis independently of lactate's function as a carbon source. LDHB silencing alters mitochondrial morphology, causes lipid peroxidation, and reduces cancer cell viability, which is potentiated by the ferroptosis inducer RSL3. Unlike LDHA, LDHB acts in parallel with glutathione peroxidase 4 (GPX4) and dihydroorotate dehydrogenase (DHODH) to suppress mitochondria-associated ferroptosis by decreasing the ubiquinone (coenzyme Q, CoQ) to ubiquinol (CoQH2) ratio. Indeed, supplementation with mitoCoQH2 (mitochondria-targeted analogue of CoQH2) suppresses mitochondrial lipid peroxidation and cell death after combined LDHB silencing and RSL3 treatment, consistent with the presence of LDHB in the cell fraction containing the mitochondrial inner membrane. Addressing the underlying molecular mechanism, an in vitro NADH consumption assay with purified human LDHB reveals that LDHB catalyzes the transfer of reducing equivalents from NADH to CoQ and that the efficiency of this reaction increases by the addition of lactate. Finally, radiation therapy induces mitochondrial lipid peroxidation and reduces tumor growth, which is further enhanced when combined with LDHB silencing. Thus, LDHB-mediated lactate oxidation drives the CoQ-dependent suppression of mitochondria-associated ferroptosis, a promising target for combination therapies.

Comparison of the effects of crizotinib as monotherapy and as combination therapy with butyric acid on different breast cancer cells

In recent years, there have been significant developments using combined therapies in cancer treatment. The present study aimed to determine the effects of using crizotinib alone and in combination with butyric acid on different types of breast cancer cells. A total of three different breast cancer models were used: MDA-MB-231, a triple negative model; MCF-7, a Luminal A model; and SKBR-3 cell line, a human epidermal growth factor receptor 2 positive model. In the experiments, proliferation rates and cell index values were obtained using the xCELLigence RTCA DP System, and mitotic index, bromodeoxyuridine labeling index and caspase activity were evaluated as cell kinetics parameters. The results showed that while proliferation rates, cell index values, mitotic index and bromodeoxyuridine labeling index decreased, caspase activity values increased. These results demonstrated that the combined application was more effective than the monotherapy application and could be used at lower concentrations than those drugs applied as monotherapy.

Discovery of novel anaplastic lymphoma kinase (ALK) and histone deacetylase (HDAC) dual inhibitors exhibiting antiproliferative activity against non-small cell lung cancer

A series of novel benzimidazole derivatives were designed and synthesised based on the structures of reported oral available ALK inhibitor and HDAC inhibitor, pracinostat. In enzymatic assays, compound 3b, containing a 2-acyliminobenzimidazole moiety and hydroxamic acid side chain, could inhibit both ALK and HDAC6 (IC50 = 16 nM and 1.03 µM, respectively). Compound 3b also inhibited various ALK mutants known to be involved in crizotinib resistance, including mutant L1196M (IC50, 4.9 nM). Moreover, 3b inhibited the proliferation of several cancer cell lines, including ALK-addicted H2228 cells. To evaluate its potential for treating cancers in vivo, 3b was used in a human A549 xenograft model with BALB/c nude mice. At 20 mg/kg, 3b inhibited tumour growth by 85% yet had a negligible effect on mean body weight. These results suggest a attracting route for the further research and optimisation of dual ALK/HDAC inhibitors.

Advances in dual-targeting inhibitors of HDAC6 for cancer treatment

Histone Deacetylase 6 (HDAC6) is an essential regulator of histone acetylation processes, exerting influence on a multitude of cellular functions such as cell motility, endocytosis, autophagy, apoptosis, and protein trafficking through its deacetylation activity. The significant implications of HDAC6 in diseases such as cancer, neurodegenerative disorders, and immune disorders have motivated extensive investigation into the development of specific inhibitors targeting this enzyme for therapeutic purposes. Single targeting drugs carry the risk of inducing drug resistance, thus prompting exploration of dual targeting therapy which offers the potential to impact multiple signaling pathways simultaneously, thereby lowering the likelihood of resistance development. While pharmacological studies have exhibited promise in combined therapy involving HDAC6, challenges related to potential drug interactions exist. In response to these challenges, researchers are investigating HDAC6 hybrid molecules which enable the concomitant targeting of HDAC6 and other key proteins, thus enhancing treatment efficacy while mitigating side effects and reducing the risk of resistance compared to traditional combination therapies. The published design strategies for dual targeting inhibitors of HDAC6 are summarized and discussed in this review. This will provide some valuable insights into more novel HDAC6 dual targeting inhibitors to meet the urgent need for innovative therapies in oncology and other related fields.

Krebs von den Lungen 6 (KL-6) is a novel diagnostic and prognostic biomarker in pleural mesothelioma

OBJECTIVES

Pleural mesothelioma (PM) is a rare disease with dismal outcome. Systemic treatment options include chemotherapy and immunotherapy, but biomarkers for treatment personalization are missing. The only FDA-approved diagnostic biomarker is the soluble mesothelin-related protein (SMRP). Krebs von den Lungen-6 (KL-6) is a human mucin 1 (MUC1) glycoprotein, which has shown diagnostic and prognostic value as a biomarker in other malignancies. The present study investigated whether KL-6 can serve as a diagnostic and/or prognostic biomarker in PM.

MATERIALS AND METHODS

Using a fully-automated chemiluminescence enzyme immunoassay (CLEIA) for KL-6 and SMRP, pleural effusion samples from 87 consecutive patients with PM and 25 patients with non-malignant pleural disorders were studied. In addition, KL-6 and SMRP levels were determined in corresponding patient sera, and in an independent validation cohort (n = 122). MUC1 mRNA and protein expression, and KL-6 levels in cell line supernatants were investigated in PM primary cell lines in vitro.

RESULTS

PM patients had significantly higher KL-6 levels in pleural effusion than non-malignant controls (AUC 0.78, p < 0.0001). Among PM patients, levels were highest in those with epithelioid or biphasic histologies. There was a strong positive correlation between pleural effusion levels of KL-6 and SMRP (p < 0.0001). KL-6 levels in sera similarly associated with diagnosis of PM, however, to a lesser extent (AUC 0.71, p = 0.008). PM patients with high pleural effusion KL-6 levels (≥303 IU/mL) had significantly better overall survival (OS) compared to those with low KL-6 levels (HR 0.51, p = 0.004). Congruently, high tumor cell MUC1 mRNA expression in primary cell lines associated with prolonged corresponding patient OS (HR 0.35, p = 0.004). These findings were confirmed in an independent validation cohort.

CONCLUSION

This is the first study demonstrating KL-6 as a potential novel liquid-based diagnostic and prognostic biomarker in PM.

Ineffectiveness of Crizotinib in a Non-Small-Cell Lung Cancer with Novel ALK- LIMS1 Fusion: A Case Report

Anaplastic lymphoma kinase (ALK) rearrangements have been reported in 3-7% of non-small-cell lung cancers (NSCLC). ALK has been reported to be fused with a variety of genes in NSCLC. Significant clinical activity was achieved by ALK inhibitors in patients with NSCLC harbouring ALK translocations. We reported on a 48-year-old male Chinese patient with advanced lung adenocarcinoma harboring a novel ALK-LIMS1 who showed no response to crizotinib. The tissue was assayed by immunohistochemistry (IHC) for ALK and showed diffuse expression of ALK. Next-generation sequencing (NGS) was performed on the peripheral blood and tissue. The previous tumor tissue showed diffuse expression of ALK. Tissue and the later peripheral blood revealed a ALK- LIMS1 fusion. The patient failed to benefit from crizotinib (250 mg, twice a day), with a progression-free survival of two months. We identified a new ALK-LIMS1 fusion from an advanced lung adenocarcinoma which was primary resistant to crizotinib. Our case suggested that the coexistence of mutations and the non-dominant clone, as well as the rearrangement of ALK fusion, did not result in expressed ALK kinase domain that might lead to no response to ALK-TKIs.

Design, synthesis and biological evaluation of 2,4-pyrimidinediamine derivatives as ALK and HDACs dual inhibitors for the treatment of ALK addicted cancer

Simultaneous inhibition of histone deacetylases (HDACs) and anaplastic lymphoma kinase (ALK) could enhance therapeutic activity against ALK addicted cancer cells. Herein, a new series of 2,4-pyrimidinediamine derivatives as ALK and HDACs dual inhibitors were designed, synthesised and evaluated. Compound 12a which possessed good inhibitory potency against ALK^wt and HDAC1, exhibited stronger antiproliferative activity than Ceritinib on ALK positive cancer cell lines though inducing cell apoptosis and cell cycle arrest in vitro and in vivo. In addition, the mechanism is further verified by the down-regulation of p-ALK protein, and up-regulation of Acetylated histone 3 (Ac-H3) protein in cancer cells. These results suggested that 12a would be a potential candidate for the ALK addicted cancer treatment.

Microbiome dysbiosis and epigenetic modulations in lung cancer: From pathogenesis to therapy

The lung microbiome plays an essential role in maintaining healthy lung function, including host immune homeostasis. Lung microbial dysbiosis or disruption of the gut-lung axis can contribute to lung carcinogenesis by causing DNA damage, inducing genomic instability, or altering the host's susceptibility to carcinogenic insults. Thus far, most studies have reported the association of microbial composition in lung cancer. Mechanistic studies describing host-microbe interactions in promoting lung carcinogenesis are limited. Considering cancer as a multifaceted disease where epigenetic dysregulation plays a critical role, epigenetic modifying potentials of microbial metabolites and toxins and their roles in lung tumorigenesis are not well studied. The current review explains microbial dysbiosis and epigenetic aberrations in lung cancer and potential therapeutic opportunities.

Histone deacetylases modulate resistance to the therapy in lung cancer

The acetylation status of histones located in both oncogenes and tumor suppressor genes modulate cancer hallmarks. In lung cancer, changes in the acetylation status are associated with increased cell proliferation, tumor growth, migration, invasion, and metastasis. Histone deacetylases (HDACs) are a group of enzymes that take part in the elimination of acetyl groups from histones. Thus, HDACs regulate the acetylation status of histones. Although several therapies are available to treat lung cancer, many of these fail because of the development of tumor resistance. One mechanism of tumor resistance is the aberrant expression of HDACs. Specific anti-cancer therapies modulate HDACs expression, resulting in chromatin remodeling and epigenetic modification of the expression of a variety of genes. Thus, HDACs are promising therapeutic targets to improve the response to anti-cancer treatments. Besides, natural compounds such as phytochemicals have potent antioxidant and chemopreventive activities. Some of these compounds modulate the deregulated activity of HDACs (e.g. curcumin, apigenin, EGCG, resveratrol, and quercetin). These phytochemicals have been shown to inhibit some of the cancer hallmarks through HDAC modulation. The present review discusses the epigenetic mechanisms by which HDACs contribute to carcinogenesis and resistance of lung cancer cells to anticancer therapies.

Targeting lactate dehydrogenase B-dependent mitochondrial metabolism affects tumor initiating cells and inhibits tumorigenesis of non-small cell lung cancer by inducing mtDNA damage

Once considered a waste product of anaerobic cellular metabolism, lactate has been identified as a critical regulator of tumorigenesis, maintenance, and progression. The putative primary function of lactate dehydrogenase B (LDHB) is to catalyze the conversion of lactate to pyruvate; however, its role in regulating metabolism during tumorigenesis is largely unknown. To determine whether LDHB plays a pivotal role in tumorigenesis, we performed 2D and 3D in vitro experiments, utilized a conventional xenograft tumor model, and developed a novel genetically engineered mouse model (GEMM) of non-small cell lung cancer (NSCLC), in which we combined an LDHB deletion allele with an inducible model of lung adenocarcinoma driven by the concomitant loss of p53 (also known as Trp53) and expression of oncogenic KRAS (G12D) (KP). Here, we show that epithelial-like, tumor-initiating NSCLC cells feature oxidative phosphorylation (OXPHOS) phenotype that is regulated by LDHB-mediated lactate metabolism. We show that silencing of LDHB induces persistent mitochondrial DNA damage, decreases mitochondrial respiratory complex activity and OXPHOS, resulting in reduced levels of mitochondria-dependent metabolites, e.g., TCA intermediates, amino acids, and nucleotides. Inhibition of LDHB dramatically reduced the survival of tumor-initiating cells and sphere formation in vitro, which can be partially restored by nucleotide supplementation. In addition, LDHB silencing reduced tumor initiation and growth of xenograft tumors. Furthermore, we report for the first time that homozygous deletion of LDHB significantly reduced lung tumorigenesis upon the concomitant loss of Tp53 and expression of oncogenic KRAS without considerably affecting the animal's health status, thereby identifying LDHB as a potential target for NSCLC therapy. In conclusion, our study shows for the first time that LDHB is essential for the maintenance of mitochondrial metabolism, especially nucleotide metabolism, demonstrating that LDHB is crucial for the survival and proliferation of NSCLC tumor-initiating cells and tumorigenesis.

Synergistic effects of FGFR1 and PLK1 inhibitors target a metabolic liability in KRAS-mutant cancer

KRAS oncoprotein is commonly mutated in human cancer, but effective therapies specifically targeting KRAS-driven tumors remain elusive. Here, we show that combined treatment with fibroblast growth factor receptor 1 (FGFR1) and polo-like kinase 1 (PLK1) inhibitors evoke synergistic cytotoxicity in KRAS-mutant tumor models in vitro and in vivo. Pharmacological and genetic suppression of FGFR1 and PLK1 synergizes to enhance anti-proliferative effects and cell death in KRAS-mutant lung and pancreatic but not colon nor KRAS wild-type cancer cells. Mechanistically, co-targeting FGFR1 and PLK1 upregulates reactive oxygen species (ROS), leading to oxidative stress-activated c-Jun N-terminal kinase (JNK)/p38 pathway and E2F1-induced apoptosis. We further delineate that autophagy protects from PLK1/FGFR1 inhibitor cytotoxicity and that antagonizing the compensation mechanism by clinically approved chloroquine fully realizes the therapeutic potential of PLK1 and FGFR1 targeting therapy, producing potent and durable responses in KRAS-mutant patient-derived xenografts and a genetically engineered mouse model of Kras-induced lung adenocarcinoma. These results suggest a previously unappreciated role for FGFR1 and PLK1 in the surveillance of metabolic stress and demonstrate a synergistic drug combination for treating KRAS-mutant cancer.

ALK-positive non-small cell lung cancer; potential combination drug treatments

Advances in chromosomally rearranged ALK positive non-small cell lung cancer have been dramatic in only the last few years. Survival times have improved dramatically due to the introduction of ever more efficacious ALK inhibitors. These improvements have been due largely to improvements in blood-brain barrier penetration and the breadth of ligand binding pocket mutations against which the drugs are effective. However, the advances maybe slow as compared to the frequency of cancers with compound resistance mutations are appearing, suggesting the need to develop multiple ALK inhibitors to target different compound mutations.Another research area that promises to provide further gains is the use of drug combinations, with an ALK inhibitor combined with a drug targeting a "second driver" to overcome resistance. In this review, the range of secondary targets for ALK+ lung cancer and the potential for their clinical success are reviewed.