Muramyl dipeptide causes mitochondrial dysfunction and intestinal inflammatory cytokine responses in rats.

INTRODUCTION: Intestinal flora and the translocation of its products, such as muramyl dipeptide (MDP), are common causes of sepsis. MDP is a common activator of the intracellular pattern recognition receptor NOD2, and MDP translocation can cause inflammatory damage to the small intestine and systemic inflammatory responses in rats. Therefore, this study investigated the effects of MDP on the intestinal mucosa and distant organs during sepsis and the role of the NOD2/AMPK/LC3 pathway in MDP-induced mitochondrial dysfunction in the intestinal epithelium. METHODS: Fifty male Sprague Dawley rats were randomly divided into five treatment groups: lipopolysaccharide (LPS) only, 1.5 and 15 mg/kg MDP + LPS, and 1.5 and 15 mg/kg MDP + short-peptide enteral nutrition (SPEN) + LPS. The total caloric intake was the same per group. The rats were euthanized 24 hours after establishing the model, and peripheral blood and small intestinal mucosal and lung tissues were collected. RESULTS: Compared to the LPS group, both MDP + LPS groups had aggravated inflammatory damage to the intestinal mucosal and lung tissues, increased IL-6 and MDP production, increased NOD2 expression, decreased AMPK and LC3 expression, increased mitochondrial reactive oxygen species production, and decreased mitochondrial membrane potential. Compared to the MDP + LPS groups, the MDP + SPEN+LPS groups had decreased IL-6 and MDP production, increased AMPK and LC3 protein expression, and protected mitochondrial and organ functions. CONCLUSIONS: MDP translocation reduced mitochondrial autophagy by regulating the NOD2/AMPK/LC3 pathway, causing mitochondrial dysfunction. SPEN protected against MDP-induced impairment of intestinal epithelial mitochondrial function during sepsis.

Design, Synthesis, and Pharmacological Evaluation of Multisubstituted Pyrido[4,3-d]pyrimidine Analogues Bearing Deuterated Methylene Linkers as Potent KRASG12D Inhibitors.

The breakthrough in drug development of KRASG12C inhibitors provides inspiration for targeting alternative KRAS mutations, especially the most prevalent KRASG12D variant. Based on the structural analysis of MRTX1133 in complex with KRASG12D, a comprehensive structure-activity study was conducted, which led to the discovery of several compounds (22, 28, and 31) that showed higher potency in suppressing the clonogenic growth of KRASG12D-dependent cancer cells. These new compounds markedly and selectively inhibited the binding of RBD peptide to GTP-bound KRASG12D with IC50 values between 0.48 and 1.21 nM. These new inhibitors were found to have dose-dependent anti-tumor efficacy in the AsPC-1 xenograft mouse models with a tumor growth inhibition of approximately 70% at a dose of 20 mg/kg twice daily (i.p.). Despite the non-optimal pharmacokinetic properties similar to those of MRTX1133, the high in vitro and in vivo potency of these new inhibitors call for further profiling.

Loss of PHF8 induces a viral mimicry response by activating endogenous retrotransposons.

Immunotherapy has become established as major treatment modality for multiple types of solid tumors, including colorectal cancer. Identifying novel immunotherapeutic targets to enhance anti-tumor immunity and sensitize current immune checkpoint blockade (ICB) in colorectal cancer is needed. Here we report the histone demethylase PHD finger protein 8 (PHF8, KDM7B), a Jumonji C domain-containing protein that erases repressive histone methyl marks, as an essential mediator of immune escape. Ablation the function of PHF8 abrogates tumor growth, activates anti-tumor immune memory, and augments sensitivity to ICB therapy in mouse models of colorectal cancer. Strikingly, tumor PHF8 deletion stimulates a viral mimicry response in colorectal cancer cells, where the depletion of key components of endogenous nucleic acid sensing diminishes PHF8 loss-meditated antiviral immune responses and anti-tumor effects in vivo. Mechanistically, PHF8 inhibition elicits H3K9me3-dependent retrotransposon activation by promoting proteasomal degradation of the H3K9 methyltransferase SETDB1 in a demethylase-independent manner. Moreover, PHF8 expression is anti-correlated with canonical immune signatures and antiviral immune responses in human colorectal adenocarcinoma. Overall, our study establishes PHF8 as an epigenetic checkpoint, and targeting PHF8 is a promising viral mimicry-inducing approach to enhance intrinsic anti-tumor immunity or to conquer immune resistance.

Discovery of a Potent and Oral Available Complex I OXPHOS Inhibitor That Abrogates Tumor Growth and Circumvents MEKi Resistance.

Targeting oxidative phosphorylation (OXPHOS) has emerged as a promising therapeutic strategy for cancer therapy. Here, we discovered a 1H-1,2,3-triazole derivative HP661 as a highly potent and orally available OXPHOS inhibitor that effectively blocked the activity of mitochondrial complex I. HP661 specifically compromised the mitochondrial oxygen consumption of high-OXPHOS lung cancer cells but not that of low-OXPHOS lung cancer cells or normal cells in the low nanomolar range. Notably, mitogen-activated protein kinase kinase (MEK) inhibitor (trametinib)-resistant lung cancer cells with high levels of OXPHOS also showed marked sensitivity to HP661, as indicated by decreased clonogenic growth and increased cell apoptosis upon treatment. In a mouse model of high-OXPHOS lung cancer, HP661 treatment not only significantly suppressed tumor growth but also augmented the therapeutic efficacy of trametinib by impairing tumor mitochondrial respiration. In summary, we identified HP661 as a highly effective OXPHOS inhibitor to abrogate the growth of high OXPHOS-dependent tumors and conquer high OXPHOS-mediated drug resistance.

Feedback activation of EGFR/wild-type RAS signaling axis limits KRASG12D inhibitor efficacy in KRASG12D-mutated colorectal cancer.

Colorectal cancer (CRC), which shows a high degree of heterogeneity, is the third most deadly cancer worldwide. Mutational activation of KRASG12D occurs in approximately 10-12% of CRC cases, but the susceptibility of KRASG12D-mutated CRC to the recently discovered KRASG12D inhibitor MRTX1133 has not been fully defined. Here, we report that MRTX1133 treatment caused reversible growth arrest in KRASG12D-mutated CRC cells, accompanied by partial reactivation of RAS effector signaling. Through a drug-anchored synthetic lethality screen, we discovered that epidermal growth factor receptor (EGFR) inhibition was synthetic lethal with MRTX1133. Mechanistically, MRTX1133 treatment downregulated the expression of ERBB receptor feedback inhibitor 1 (ERRFI1), a crucial negative regulator of EGFR, thereby causing EGFR feedback activation. Notably, wild-type isoforms of RAS, including H-RAS and N-RAS, but not oncogenic K-RAS, mediated signaling downstream of activated EGFR, leading to RAS effector signaling rebound and reduced MRTX1133 efficacy. Blockade of activated EGFR with clinically used antibodies or kinase inhibitors suppressed the EGFR/wild-type RAS signaling axis, sensitized MRTX1133 monotherapy, and caused the regression of KRASG12D-mutant CRC organoids and cell line-derived xenografts. Overall, this study uncovers feedback activation of EGFR as a prominent molecular event that restricts KRASG12D inhibitor efficacy and establishes a potential combination therapy consisting of KRASG12D and EGFR inhibitors for patients with KRASG12D-mutated CRC.

Targeting metabolic vulnerability in mitochondria conquers MEK inhibitor resistance in KRAS-mutant lung cancer.

MEK is a canonical effector of mutant KRAS; however, MEK inhibitors fail to yield satisfactory clinical outcomes in KRAS-mutant cancers. Here, we identified mitochondrial oxidative phosphorylation (OXPHOS) induction as a profound metabolic alteration to confer KRAS-mutant non-small cell lung cancer (NSCLC) resistance to the clinical MEK inhibitor trametinib. Metabolic flux analysis demonstrated that pyruvate metabolism and fatty acid oxidation were markedly enhanced and coordinately powered the OXPHOS system in resistant cells after trametinib treatment, satisfying their energy demand and protecting them from apoptosis. As molecular events in this process, the pyruvate dehydrogenase complex (PDHc) and carnitine palmitoyl transferase IA (CPTIA), two rate-limiting enzymes that control the metabolic flux of pyruvate and palmitic acid to mitochondrial respiration were activated through phosphorylation and transcriptional regulation. Importantly, the co-administration of trametinib and IACS-010759, a clinical mitochondrial complex I inhibitor that blocks OXPHOS, significantly impeded tumor growth and prolonged mouse survival. Overall, our findings reveal that MEK inhibitor therapy creates a metabolic vulnerability in the mitochondria and further develop an effective combinatorial strategy to circumvent MEK inhibitors resistance in KRAS-driven NSCLC.

BCL6 is regulated by the MAPK/ELK1 axis and promotes KRAS-driven lung cancer.

Mutational activation of KRAS is a common oncogenic event in lung cancer, yet effective therapies are still lacking. Here, we identify B cell lymphoma 6 (BCL6) as a lynchpin in KRAS-driven lung cancer. BCL6 expression was increased upon KRAS activation in lung tumor tissue in mice and was positively correlated with the expression of KRAS-GTP, the active form of KRAS, in various human cancer cell lines. Moreover, BCL6 was highly expressed in human KRAS-mutant lung adenocarcinomas and was associated with poor patient survival. Mechanistically, the MAPK/ERK/ELK1 signaling axis downstream of mutant KRAS directly regulated BCL6 expression. BCL6 maintained the global expression of prereplication complex components; therefore, BCL6 inhibition induced stalling of the replication fork, leading to DNA damage and growth arrest in KRAS-mutant lung cancer cells. Importantly, BCL6-specific knockout in lungs significantly reduced the tumor burden and mortality in the LSL-KrasG12D/+ lung cancer mouse model. Likewise, pharmacological inhibition of BCL6 significantly impeded the growth of KRAS-mutant lung cancer cells both in vitro and in vivo. In summary, our findings reveal a crucial role of BCL6 in promoting KRAS-addicted lung cancer and suggest BCL6 as a therapeutic target for the treatment of this intractable disease.

Protective effect of ghrelin on intestinal I/R injury in rats.

This study aimed to investigate whether ghrelin affected the autophagy and inflammatory response of intestinal intraepithelial lymphocytes (IELs) by regulating the NOD2/Beclin-1 pathway in an intestinal ischemia-reperfusion (I/R) injury model. Twenty hours after implementing the intestinal I/R injury rat model, the small intestine and both lungs were collected for histological analysis. The morphological changes in the intestinal mucosa epithelium and lung tissues were evaluated using hematoxylin-eosin staining. The activity of autophagic vacuoles and organ injury were evaluated using electron microscopy. The cytokine levels (IL-10 and TNF-α) in IEL cells and lung tissue were determined using enzyme-linked immunosorbent assay. RT-qPCR and western blot assays were conducted to check the NOD2, Beclin-1, and ATG16 levels. Ghrelin relieved the I/R-induced destruction of the intestinal mucosa epithelium and lung tissues. Moreover, ghrelin enhanced autophagy in the intestinal epithelium and lungs of I/R rats. In addition, the levels of autophagy-associated proteins (Beclin-1, ATG16, and NOD2) were higher in the ghrelin treatment group than in rats with I/R. Ghrelin reduced significantly the IL-10 and TNF-α levels. However, these changes were reversed by the NOD2 antagonist. In conclusion, ghrelin may relieve I/R-induced acute intestinal mucosal damage, autophagy disorder, and inflammatory response in IELs by regulating the NOD2/Beclin-1 pathway.

The oncoprotein BCL6 enables solid tumor cells to evade genotoxic stress.

Genotoxic agents remain the mainstay of cancer treatment. Unfortunately, the clinical benefits are often countered by a rapid tumor adaptive response. Here, we report that the oncoprotein B cell lymphoma 6 (BCL6) is a core component that confers solid tumor adaptive resistance to genotoxic stress. Multiple genotoxic agents promoted BCL6 transactivation, which was positively correlated with a weakened therapeutic efficacy and a worse clinical outcome. Mechanistically, we discovered that treatment with the genotoxic agent etoposide led to the transcriptional reprogramming of multiple pro-inflammatory cytokines, among which the interferon-α and interferon-γ responses were substantially enriched in resistant cells. Our results further revealed that the activation of interferon/signal transducer and activator of transcription 1 axis directly upregulated BCL6 expression. The increased expression of BCL6 further repressed the tumor suppressor PTEN and consequently enabled resistant cancer cell survival. Accordingly, targeted inhibition of BCL6 remarkably enhanced etoposide-triggered DNA damage and apoptosis both in vitro and in vivo. Our findings highlight the importance of BCL6 signaling in conquering solid tumor tolerance to genotoxic stress, further establishing a rationale for a combined approach with genotoxic agents and BCL6-targeted therapy.

YYFZBJS inhibits colorectal tumorigenesis by enhancing Tregs-induced immunosuppression through HIF-1α mediated hypoxia in vivo and in vitro.

BACKGROUND AND PURPOSE: The occurrence of colorectal cancer (CRC) is associated with a variety of factors. Accumulating evidence shows that peripheral differentiation of regulatory T cells (Tregs) is critical in controlling tumorigenesis. Our previous studies demonstrated that the Yi-Yi-Fu-Zi-Bai-Jiang-San (YYFZBJS) extract exerted potent anticancer activities by significantly enhancing immunosuppression in ApcMin/+ mice. However, there is limited knowledge on the effect of YYFZBJS in the prevention of colorectal cancer and the underlying mechanisms of action. METHODS: In this study, we investigated the effect of oral administration of YYFZBJS in preventing azoxymethane (AOM)/dextran sulfate sodium (DSS)-induced tumorigenesis. We found that YYFZBJS treatment decreased tumor load, tumor number, histology, and the severity of disease activity index (DAI) scores. To investigate if YYFZBJS inhibited tumorigenesis by regulating regulatory T cells, we depleted Tregs in AOM/DSS mice. We then analyzed the effect of intragastric administration of YYFZBJS on tumorigenesis and the regulation of tumor microenvironment. RESULTS: As expected, intragastric administration of YYFZBJS in AOM/DSS mice model significantly increased immune responses in the tumor microenvironment through its hypoxia-associated anti-cancer activities. Additionally, YYFZBJS regulated the polarization of peripheral Treg (pTreg) to suppress CRC cell proliferation and infiltration. This was demonstrated by the decrease in tumor proliferation-related proteins including p-STAT3, p-NF-κB and MMPs in a dose-dependent manner. Clinically, the increase in the levels of Tregs in human tissues during CRC progression was associated with low expression of HIF-1α in the stroma, and correlated with CRC survival and prognosis. CONCLUSION: Altogether, we demonstrated that HIF-1α may promote pTreg -induced carcinogenesis and progression of CRC cells, indicating that YYFZBJS is a promising protective agent against HIF-1α-mediated Treg activation in colorectal cancer. This study is the first to imply a novel clinical significance of a traditional Chinese herbal medicine from Synopsis of Golden Chamber in the cancer treatment and clarify the important role of tumor microenvironment in preventing tumorigenesis.

Design, synthesis, and biological evaluation of indole-based hydroxamic acid derivatives as histone deacetylase inhibitors.

The equilibrium between histone acetylation and deacetylation plays an important role in cancer initiation and progression. The histone deacetylases (HDACs) are a class of key regulators of gene expression that enzymatically remove an acetyl moiety from acetylated lysine ε-amino groups on histone tails. Therefore, HDAC inhibitors have recently emerged as a promising strategy for cancer therapy and several pan-HDAC inhibitors have globally been approved for clinical use. In the present study, we designed and synthesized a series of substituted indole-based hydroxamic acid derivatives that exhibited potent anti-proliferative activities in various tumor cell lines. Among the compounds tested, compound 4o, was found to be among the most potent in the inhibition of HDAC1 (half maximal inhibitory concentration, IC50 = 1.16 nM) and HDAC6 (IC50 = 2.30 nM). It also exhibited excellent in vitro anti-tumor proliferation activity. Additionally, compound 4o effectively increased the acetylation of histone H3 in a dose-dependent manner and inhibited cell proliferation by inducing cell cycle arrest and apoptosis. Moreover, compound 4o remarkably blocked colony formation in HCT116 cancer cells. Based on its favorable in vitro profile, compound 4o was further evaluated in an HCT116 xenograft mouse model, in which it demonstrated better in vivo efficacy than the clinically used HDAC inhibitor, suberanilohydroxamic acid. Interestingly, compound 4k was found to have a preference for the inhibition of HDAC6, with IC50 values of 115.20 and 5.29 nM against HDAC1 and HDAC6, respectively.

BCL6 confers KRAS-mutant non-small-cell lung cancer resistance to BET inhibitors.

The bromodomain and extra-terminal domain (BET) proteins are promising therapeutic targets to treat refractory solid tumors; however, inherent resistance remains a major challenge in the clinic. Recently, the emerging role of the oncoprotein B cell lymphoma 6 (BCL6) in tumorigenesis and stress response has been unveiled. Here, we demonstrate that BCL6 was upregulated upon BET inhibition in KRAS-mutant cancers, including non-small-cell lung cancer (NSCLC). We further found that BRD3, not BRD2 or BRD4, directly interacted with BCL6 and maintained the negative autoregulatory circuit of BCL6. Disrupting this negative autoregulation by BET inhibitors (BETi) resulted in a striking increase in BCL6 transcription, which further activated the mTOR signaling pathway through repression of the tumor suppressor death-associated protein kinase 2. Importantly, pharmacological inhibition of either BCL6 or mTOR improved the tumor response and enhanced the sensitivity of KRAS-mutant NSCLC to BETi in both in vitro and in vivo settings. Overall, our findings identify a mechanism of BRD3-mediated BCL6 autoregulation and further develop an effective combinatorial strategy to circumvent BETi resistance in KRAS-driven NSCLC.

Erk and MAPK signaling is essential for intestinal development through Wnt pathway modulation.

Homeostasis of intestinal stem cells (ISCs) is maintained by the orchestration of niche factors and intrinsic signaling networks. Here, we have found that deletion of Erk1 and Erk2 (Erk1/2) in intestinal epithelial cells at embryonic stages resulted in an unexpected increase in cell proliferation and migration, expansion of ISCs, and formation of polyp-like structures, leading to postnatal death. Deficiency of epithelial Erk1/2 results in defects in secretory cell differentiation as well as impaired mesenchymal cell proliferation and maturation. Deletion of Erk1/2 strongly activated Wnt signaling through both cell-autonomous and non-autonomous mechanisms. In epithelial cells, Erk1/2 depletion resulted in loss of feedback regulation, leading to Ras/Raf cascade activation that transactivated Akt activity to stimulate the mTor and Wnt/ß-catenin pathways. Moreover, Erk1/2 deficiency reduced the levels of Indian hedgehog and the expression of downstream pathway components, including mesenchymal Bmp4 - a Wnt suppressor in intestines. Inhibition of mTor signaling by rapamycin partially rescued Erk1/2 depletion-induced intestinal defects and significantly prolonged the lifespan of mutant mice. These data demonstrate that Erk/Mapk signaling functions as a key modulator of Wnt signaling through coordination of epithelial-mesenchymal interactions during intestinal development.

Dual base editor catalyzes both cytosine and adenine base conversions in human cells.

Although base editors are useful tools for precise genome editing, current base editors can only convert either adenines or cytosines. We developed a dual adenine and cytosine base editor (A&C-BEmax) by fusing both deaminases with a Cas9 nickase to achieve C-to-T and A-to-G conversions at the same target site. Compared to single base editors, A&C-BEmax's activity on adenines is slightly reduced, whereas activity on cytosines is higher and RNA off-target activity is substantially decreased.

Detection of miR-155-5p and imaging lung cancer for early diagnosis: in vitro and in vivo study.

PURPOSE: Currently, the routine screening program has insufficient capacity for the early diagnosis of lung cancer. Therefore, a type of chitosan-molecular beacon (CS-MB) probe was developed to recognize the miR-155-5p and image the lung cancer cells for the early diagnosis. METHODS: Based on the molecular beacon (MB) technology and nanotechnology, the CS-MB probe was synthesized self-assembly. There are four types of cells-three kinds of animal models and one type of histopathological sections of human lung cancer were utilized as models, including A549, SPC-A1, H446 lung cancer cells, tumor-initiating cells (TICs), subcutaneous and lung xenografts mice, and lox-stop-lox(LSL) K-ras G12D transgenic mice. The transgenic mice dynamically displayed the process from normal lung tissues to atypical hyperplasia, adenoma, carcinoma in situ, and adenocarcinoma. The different miR-155-5p expression levels in these cells and models were measured by quantitative real-time polymerase chain reaction (qRT-PCR). The CS-MB probe was used to recognize the miR-155-5p and image the lung cancer cells by confocal microscopy in vitro and by living imaging system in vivo. RESULTS: The CS-MB probe could be used to recognize the miR-155-5p and image the lung cancer cells significantly in these cells and models. The fluorescence intensity trends detected by the CS-MB probe were similar to the expression levels trends of miR-155 tested by qRT-PCR. Moreover, the fluorescence intensity showed an increasing trend with the tumor progression in the transgenic mice model, and the occurrence and development of lung cancer were dynamically monitored by the differen fluorescence intensity. In addition, the miR-155-5p in human lung cancer tissues could be detected by the miR-155-5p MB. CONCLUSION: Both in vivo and in vitro experiments demonstrated that the CS-MB probe could be utilized to recognize the miR-155-5p and image the lung cancer cells. It provided a novel experimental and theoretical basis for the early diagnosis of the disease. Also, the histopathological sections of human lung cancer research laid the foundation for subsequent preclinical studies. In addition, different MBs could be designed to detect other miRNAs for the early diagnosis of other tumors.

Blocking STAT3 by pyrvinium pamoate causes metabolic lethality in KRAS-mutant lung cancer.

Signal transducer and activator of transcription 3 (STAT3) exerts a profound role in regulating mitochondrial function and cellular metabolism. Mitochondrial STAT3 supports RAS-dependent malignant transformation and tumor growth. However, whether pharmacological blockade of STAT3 leads to metabolic lethality in KRAS-mutant lung cancer remains unclear. Pyrvinium pamoate, a clinical antihelminthic drug, preferentially inhibited the growth of KRAS-mutant lung cancer cells in vitro and in vivo. Mechanistic study revealed that pyrvinium dose-dependently suppressed STAT3 phosphorylation at tyrosine 705 and serine 727. Overexpression mitochondrial STAT3 prominently weakened the therapeutic efficacy of pyrvinium. As a result of targeting STAT3, pyrvinium selectively triggered reactive oxygen species release, depolarized mitochondrial membrane potential and suppressed aerobic glycolysis in KRAS-mutant lung cancer cells. Importantly, the cytotoxic effects of pyrvinium could be significantly augmented by glucose deprivation both in vitro and in a patient-derived lung cancer xenograft mouse model in vivo. The combined efficacy significantly correlated with intratumoural STAT3 suppression. Our findings reveal that KRAS-mutant lung cancer cells are vulnerable to STAT3 inhibition exerted by pyrvinium, providing a promising direction for developing therapies targeting STAT3 and metabolic synthetic lethality for the treatment of KRAS-mutant lung cancer.

The Bcr-Abl inhibitor GNF-7 inhibits necroptosis and ameliorates acute kidney injury by targeting RIPK1 and RIPK3 kinases.

Necroptosis is a form of programmed, caspase-independent cell death that is involved in various pathologic disorders such as ischemia/reperfusion injury, acute kidney injury and inflammatory bowel diseases. Identification of necroptosis inhibitors has great therapeutic potential for the treatment of necroptosis-associated diseases. In this study, we identified that the Bcr-Abl inhibitor GNF-7 was a potent inhibitor of necroptosis. GNF-7 inhibited necroptosis in both human and mouse cells, while not protecting cells from apoptosis. Drug affinity responsive target stability assay (DARTS) demonstrated that it binded with RIPK1 and RIPK3. GNF-7 inhibited RIPK1 and RIPK3 kinase activities and thus disrupted RIPK1-RIPK3 necrosome complex formation. In vivo, GNF-7 ameliorated both cisplatin- and ischemia/reperfusion-induced AKI. Orally administration of GNF-7 attenuated renal cell necrosis and reduced pro-inflammatory responses in mouse models of AKI. Taken together, our study shows that GNF-7 is a novel necroptosis inhibitor and has great potential for the treatment of acute renal inflammatory disorders by targeting both RIPK1 and RIPK3 kinases.

Pracinostat (SB939), a histone deacetylase inhibitor, suppresses breast cancer metastasis and growth by inactivating the IL-6/STAT3 signalling pathways.

AIMS: Histone deacetylases inhibitors have shown favorable antitumor activity in clinical investigations. In the present study, we assessed the effects of a novel hydroxamic acid-based HDAC inhibitor, SB939, on breast cancer metastasis and tumor growth and characterized the underlying molecular mechanisms. MAIN METHODS: MTS, Wound-healing, and Transwell chamber invasion assays were used to detect the inhibition effects of SB939 on proliferation, migration, and invasion of breast cancer cells. Western blot, cellular immunofluorescence, and EMSA were used to explore the molecular mechanism of SB939 in suppressing breast cancer metastasis. MDA-MB-231 subcutaneous tumor-bearing model of nude mice and the spontaneous metastasis model of breast cancer were both applied to verify in vivo anti-tumor growth and anti-metastatic effects. KEY FINDINGS: Our results demonstrated that SB939 at 0.5-1 µmol/L markedly impaired the chemotactic motility of breast cancer cells. SB939 reversed epithelial-mesenchymal transition (EMT) process, as evidenced by upregulation E-cadherin expression and downregulation expressions of N-cadherin and vimentin through increasing the levels of ac-histone H3 and H4 and drecreasing the expressiongs of HDAC 5 and 4. This cascade inhibition mediated by SB939 was well interpreted by inactivating phosphorylation of STAT3, blocking its DNA-binding activity, and decreasing the expressions of STAT3-dependent target genes, including MMP2 and MMP9. Furhtermore, we found that SB939 significantly inhibited breast cancer metastasis and tumor growth in vivo and showed superior anti-tumor properties compared with SAHA in two breast cancer animal models. SIGNIFICANCE: Our findings indicate that SB939 may be an effective therapeutic option for treating advanced breast cancer.

Synthesis and Biological Evaluation of B-Cell Lymphoma 6 Inhibitors of N-Phenyl-4-pyrimidinamine Derivatives Bearing Potent Activities against Tumor Growth.

The transcriptional repressor B-cell lymphoma 6 (BCL6) is frequently misregulated in diffuse large B-cell lymphoma (DLBCL) and has emerged as an attractive drug target for the treatments of lymphoma. In this article, a series of N-phenyl-4-pyrimidinamine derivatives were designed and synthesized as potent BCL6 inhibitors by optimizing hit compound N4-(3-chloro-4-methoxyphenyl)-N2-isobutyl-5-fluoro-2,4-pyrimidinediamine on the basis of the structure-activity relationship. Among them, compound 14j displayed the most potent activities, which significantly blocked the interaction of BCL6 with its corepressors, reactivated BCL6 target genes in a dose-dependent manner, and had better effects compared with the two positive controls. Further studies indicated that a low dose of 14j could effectively inhibit germinal center formation. More importantly, 14j not only showed potent inhibition of DLBCL cell proliferation in vitro but also strongly suppressed the growth of DLBCL in vivo.

Suppression of the SLC7A11/glutathione axis causes synthetic lethality in KRAS-mutant lung adenocarcinoma.

Oncogenic KRAS is a major driver in lung adenocarcinoma (LUAD) that has yet to be therapeutically conquered. Here we report that the SLC7A11/glutathione axis displays metabolic synthetic lethality with oncogenic KRAS. Through metabolomics approaches, we found that mutationally activated KRAS strikingly increased intracellular cystine levels and glutathione biosynthesis. SLC7A11, a cystine/glutamate antiporter conferring specificity for cystine uptake, was overexpressed in patients with KRAS-mutant LUAD and showed positive association with tumor progression. Furthermore, SLC7A11 inhibition by either genetic depletion or pharmacological inhibition with sulfasalazine resulted in selective killing across a panel of KRAS-mutant cancer cells in vitro and tumor growth inhibition in vivo, suggesting the functionality and specificity of SLC7A11 as a therapeutic target. Importantly, we further identified a potent SLC7A11 inhibitor, HG106, that markedly decreased cystine uptake and intracellular glutathione biosynthesis. Furthermore, HG106 exhibited selective cytotoxicity toward KRAS-mutant cells by increasing oxidative stress- and ER stress-mediated cell apoptosis. Of note, treatment of KRAS-mutant LUAD with HG106 in several preclinical lung cancer mouse models led to marked tumor suppression and prolonged survival. Overall, our findings reveal that KRAS-mutant LUAD cells are vulnerable to SLC7A11 inhibition, offering potential therapeutic approaches for this currently incurable disease.