Metformin inhibits lung cancer cells proliferation through repressing microRNA-222

Metformin, which is commonly used as an oral anti-hyperglycemic agent of the biguanide family, may reduce cancer risk and improve prognosis. However, the mechanism by which metformin affects various cancers, including lung cancer, remains unknown. MiR-222 induces cell growth and cell cycle progression via direct targeting of p27, p57 and PTEN in cancer cells. In the present study, we used A549 and NCI-H358 human lung cancer cell lines to study the effects and mechanisms of metformin. Metformin treatment reduced expression of miR-222 in these cells (p < 0.05). As a result, protein abundance of p27, p57 and PTEN were increased in cells exposed to metformin. Therefore, these data provide novel evidence for a mechanism that may contribute to the anti-neoplastic effects of metformin suggested by recent population studies and justifying further work to explore potential roles for it in lung cancer treatment.     

TRAIL耐药产生的机制及逆转耐药的最新策略

肿瘤坏死因子相关凋亡诱导配体（tumor necrosis factor-related apoptosis inducing li-gand,TRAIL）是唯一能诱导癌细胞凋亡而对机体正常组织无明显损伤的内源性细胞因子,因而被认为是一种极具前景的抗癌药物。然而目前研究发现,许多恶性肿瘤细胞对TRAIL具有耐药性,使TRAIL在临床应用中遭遇瓶颈。越来越多的证据表明,一些关键信号通路可能与TRAIL耐药有关,且利用靶向基因治疗策略以及借助某些天然药物或小分子抑制剂能够部分恢复癌细胞对TRAIL的敏感性。该文主要描述了肿瘤细胞对TRAIL的耐药机制,并对如何有效克服和逆转TRAIL耐药的策略作了简要概括。     

Effect of metformin on stem cells: Molecular mechanism and clinical prospect

Metformin is a first-line medication for type II diabetes. Numerous studies have shown that metformin not only has hypoglycemic effects, but also modulates many physiological and pathological processes ranging from aging and cancer to fracture healing. During these different physiological activities and pathological changes, stem cells usually play a core role. Thus, many studies have investigated the effects of metformin on stem cells. Metformin affects cell differentiation and has promising applications in stem cell medicine. It exerts anti-aging effects and can be applied to gerontology and regenerative medicine. The potential anti-cancer stem cell effect of metformin indicates that it can be an adjuvant therapy for cancers. Furthermore, metformin has beneficial effects against many other diseases including cardiovascular and autoimmune diseases. In this review, we summarize the effects of metformin on stem cells and provide an overview of its molecular mechanisms and clinical prospects.     

Homoharringtonine inhibited breast cancer cells growth via miR-18a-3p/AKT/mTOR signaling pathway

Homoharringtonine (HHT), a natural alkaloid derived from the cephalotaxus, exhibited its anti-cancer effects in hematological malignancies clinically. However, its pesticide effects and mechanisms in treating solid tumors remain unclear. In this study, we found that HHT was capable of inhibiting tumor growth after 5-days treatment of breast cancer cells, MCF-7, in vivo. Furthemore, HHT also significantly inhibited the cancer cell growth and induced cell apoptosis in vitro. miRNA sequencing proved miR-18a-3p was noticeably downregulated in the cells after HHT treatment. Moreover, downregulating miR-18a-3p increased HHT-induced cell apoptosis; our data supported that HHT suppressed miR-18a-3p expression and inhibited tumorigenesis might via AKT-mTOR signaling pathway. In conclusion: our study proved that HHT suppressed breast cancer cell growth and promoted apoptosis mediated by regulating of the miR-18a-3p-AKT-mTOR signaling pathway, HHT may be a promising antitumor agent in breast cancer treatment.     

PTHrP Overexpression Increases Sensitivity of Breast Cancer Cells to Apo2L/TRAIL

Parathyroid hormone-related protein (PTHrP) is a key component in breast development and breast tumour biology. PTHrP has been discovered as a causative agent of hypercalcaemia of malignancy and is also one of the main factors implicated in breast cancer mediated osteolysis. Clinical studies have determined that PTHrP expression by primary breast cancers was an independent predictor of improved prognosis. Furthermore, PTHrP has been demonstrated to cause tumour cell death both in vitro and in vivo. Apo2L/TRAIL is a promising new anti-cancer agent, due to its ability to selectively induce apoptosis in cancer cells whilst sparing most normal cells. However, some cancer cells are resistant to Apo2L/TRAIL-induced apoptosis thus limiting its therapeutic efficacy. The effects of PTHrP on cell death signalling pathways initiated by Apo2L/TRAIL were investigated in breast cancer cells. Expression of PTHrP in Apo2L/TRAIL resistant cell line MCF-7 sensitised these cells to Apo2L/TRAIL-induced apoptosis. The actions of PTHrP resulted from intracellular effects, since exogenous treatment of PTHrP had no effect on Apo2L/TRAIL-induced apoptosis. Apo2L/TRAIL-induced apoptosis in PTHrP expressing cells occurred through the activation of caspase-10 resulting in caspase-9 activation and induction of apoptosis through the effector caspases, caspase-6 and -7. PTHrP increased cell surface expression of Apo2L/TRAIL death receptors, TRAIL-R1 and TRAIL-R2. Antagonistic antibodies against the death receptors demonstrated that Apo2L/TRAIL mediated its apoptotic signals through activation of the TRAIL-R2 in PTHrP expressing breast cancer cells. These studies reveal a novel role for PTHrP with Apo2L/TRAIL that maybe important for future diagnosis and treatment of breast cancer.     

Effect of Metformin Use on Survival in Resectable Pancreatic Cancer: A Single-Institution Experience and Review of the Literature

Observational studies have demonstrated that metformin use in diabetic patients is associated with reduced cancer incidence and mortality. Here, we aimed to determine whether metformin use was associated with improved survival in patients with resected pancreatic cancer. All patients with diabetes who underwent resection for pancreatic adenocarcinoma between 12/1/1986 and 4/30/2013 at our institution were categorized by metformin use. Survival analysis was done using the Kaplan-Meier method, with log-rank test and Cox proportional hazards multivariable regression models. For analyses of our data and the only other published study, we used Meta-Analysis version 2.2. We identified 44 pancreatic cancer patients with diabetes who underwent resection of the primary tumor (19 with ongoing metformin use, 25 never used metformin). There were no significant differences in major clinical and demographic characteristics between metformin and non-metformin users. Metformin users had a better median survival than nonusers, but the difference was not statistically significant (35.3 versus 20.2 months; P = 0.3875). The estimated 2-, 3-, and 5-year survival rates for non-metformin users were 42%, 28%, and 14%, respectively. Metformin users fared better with corresponding rates of 68%, 34%, and 34%, respectively. In our literature review, which included 111 patients from the two studies (46 metformin users and 65 non-users), overall hazard ratio was 0.668 (95% CI 0.397–1.125), with P = 0.129. Metformin use was associated with improved survival outcomes in patients with resected pancreatic cancer, but the difference was not statistically significant. The potential benefit of metformin should be investigated in adequately powered prospective studies.     

The combination of metformin and 2 deoxyglucose inhibits autophagy and induces AMPK-dependent apoptosis in prostate cancer cells

Targeting cancer cell metabolism is a new promising strategy to fight cancer. Metformin, a widely used antidiabetic agent, and 2-deoxyglucose (2DG) drastically affect cancer cell metabolism. Recently, we showed that the combination of the two drugs was much more harmful for cancer cells than the treatment with metformin or 2DG alone. At the cellular level, this combination leads to p53- and AMPK-dependent apoptosis. Furthermore, we showed that metformin inhibits 2DG-induced autophagy, decreases beclin 1 expression and triggers a switch from a survival process to cell death.     

miR-326-Histone Deacetylase-3 Feedback Loop Regulates the Invasion and Tumorigenic and Angiogenic Response to Anti-cancer Drugs

Histone modification is known to be associated with multidrug resistance phenotypes. Cancer cell lines that are resistant or have been made resistant to anti-cancer drugs showed lower expression levels of histone deacetylase-3 (HDAC3), among the histone deacetylase(s), than cancer cell lines that were sensitive to anti-cancer drugs. Celastrol and Taxol decreased the expression of HDAC3 in cancer cell lines sensitive to anti-cancer drugs. HDAC3 negatively regulated the invasion, migration, and anchorage-independent growth of cancer cells. HDAC3 conferred sensitivity to anti-cancer drugs in vitro and in vivo. TargetScan analysis predicted miR-326 as a negative regulator of HDAC3. ChIP assays and luciferase assays showed a negative feedback loop between HDAC3 and miR-326. miR-326 decreased the apoptotic effect of anti-cancer drugs, and the miR-326 inhibitor increased the apoptotic effect of anti-cancer drugs. miR-326 enhanced the invasion and migration potential of cancer cells. The miR-326 inhibitor negatively regulated the tumorigenic, metastatic, and angiogenic potential of anti-cancer drug-resistant cancer cells. HDAC3 showed a positive feedback loop with miRNAs such as miR-200b, miR-217, and miR-335. miR-200b, miR-217, and miR-335 negatively regulated the expression of miR-326 and the invasion and migration potential of cancer cells while enhancing the apoptotic effect of anti-cancer drugs. TargetScan analysis predicted miR-200b and miR-217 as negative regulators of cancer-associated gene, a cancer/testis antigen, which is known to regulate the response to anti-cancer drugs. HDAC3 and miR-326 acted upstream of the cancer-associated gene. Thus, we show that the miR-326-HDAC3 feedback loop can be employed as a target for the development of anti-cancer therapeutics.     

Acrolein sensitizes human renal cancer Caki cells to TRAIL-induced apoptosis via ROS-mediated up-regulation of death receptor-5 (DR5) and down-regulation of Bcl-2

TRAIL resistance in many cancer cells is one of the major problems in TRAIL-based cancer therapy. Thus, the agents that can sensitize the tumor cells to TRAIL-mediated apoptosis are strictly needed for the improvement of anti-cancer effect of TRAIL. Acrolein is a byproduct of lipid peroxidation, which has been involved in pulmonary, cardiac and neurodegenerative diseases. We investigated whether acrolein, an α,β-unsaturated aldehyde, can potentiate TRAIL-induced apoptosis in human renal cancer cells. The combined treatment with acrolein and TRAIL significantly induced apoptosis, and stimulated of caspase-3 activity, DNA fragmentation, and cleavage of PARP. We found that acrolein down-regulated the protein level of Bcl-2 and Bcl-2 overexpression inhibited the cell death induced by the combined treatment with acrolein and TRAIL. In addition, acrolein up-regulated C/EBP homologous protein (CHOP) and TRAIL death receptor 5 (DR5) and down-regulation of CHOP or DR5 expression using the respective small interfering RNA significantly attenuated the apoptosis induced by acrolein plus TRAIL. Interestingly, pretreatment with an antioxidant, N-acetylcysteine (NAC), inhibited not only CHOP and DR5 up-regulation but also the cell death induced by acrolein plus TRAIL. Taken together, our results demonstrated that acrolein enhances TRAIL-induced apoptosis in Caki cells through down-regulation of Bcl-2 and ROS dependent up-regulation of DR5.     

二甲双胍在II型糖尿病合并肝癌中的研究进展

多年来二甲双胍以其安全性高、价格低及疗效好的优点而广泛应用于临床治疗糖尿病。糖尿病增加了肝癌的罹患率并影响其预后。近年来研究发现二甲双胍在治疗Ⅱ型糖尿病(T2MD)患者时亦降低了其罹患肝癌的风险,大量研究证明其具有抗癌及协同抗癌作用。现本文对二甲双胍在Ⅱ型糖尿病患者中对肝癌发生的影响进行探讨,对二甲双胍抑制肿瘤的分子生物学机制进行了介绍,列举了最新的实验研究数据,并对现有临床数据进行分析,对于二甲双胍未来的研究方向提出了预期,对于二甲双胍未来在Ⅱ型糖尿病患者中肝癌的预防作用进行了简要的总结及未来使用的展望,对于其在Ⅱ型糖尿病合并肝癌的患者中的治疗作用进行了前瞻性的探讨,为二甲双胍在其他癌症防治中的应用提出了可能性。     

The combination of TRAIL and luteolin enhances apoptosis in human cervical cancer HeLa cells

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is one of the most promising candidates for cancer therapeutics. However, some tumor cells are resistant to TRAIL-induced apoptosis. Our previous studies have shown that luteolin, a naturally occurring flavonoid, induces the up-regulation of death receptor 5 (DR5), which is a receptor for TRAIL. Here, we show for the first time that luteolin synergistically acts with exogenous soluble recombinant human TRAIL to induce apoptosis in HeLa cells, but not in normal human peripheral blood mononuclear cells. The combined use of luteolin and TRAIL induced Bid cleavage and the activation of caspase-8. Also, human recombinant DR5/Fc chimera protein, caspase inhibitors, and DR5 siRNA efficiently reduced apoptosis induced by co-treatment with luteolin and TRAIL. These results raise the possibility that this combined treatment with luteolin and TRAIL might be promising as a new therapy against cancer.     

The Oncogene Metadherin Modulates the Apoptotic Pathway Based on the Tumor Necrosis Factor Superfamily Member TRAIL (Tumor Necrosis Factor-related Apoptosis-inducing Ligand) in Breast Cancer

Metadherin (MTDH), the newly discovered gene, is overexpressed in more than 40% of breast cancers. Recent studies have revealed that MTDH favors an oncogenic course and chemoresistance. With a number of breast cancer cell lines and breast tumor samples, we found that the relative expression of MTDH correlated with tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) sensitivity in breast cancer. In this study, we found that knockdown of endogenous MTDH cells sensitized the MDA-MB-231 cells to TRAIL-induced apoptosis both in vitro and in vivo. Conversely, stable overexpression of MTDH in MCF-7 cells enhanced cell survival with TRAIL treatment. Mechanically, MTDH down-regulated caspase-8, decreased caspase-8 recruitment into the TRAIL death-inducing signaling complex, decreased caspase-3 and poly(ADP-ribose) polymerase-2 processing, increased Bcl-2 expression, and stimulated TRAIL-induced Akt phosphorylation, without altering death receptor status. In MDA-MB-231 breast cancer cells, sensitization to TRAIL upon MTDH down-regulation was inhibited by the caspase inhibitor Z-VAD-fmk (benzyloxycarbonyl-VAD-fluoromethyl ketone), suggesting that MTDH depletion stimulates activation of caspases. In MCF-7 breast cancer cells, resistance to TRAIL upon MTDH overexpression was abrogated by depletion of Bcl-2, suggesting that MTDH-induced Bcl-2 expression contributes to TRAIL resistance. We further confirmed that MTDH may control Bcl-2 expression partly by suppressing miR-16. Collectively, our results point to a protective function of MTDH against TRAIL-induced death, whereby it inhibits the intrinsic apoptosis pathway through miR-16-mediated Bcl-2 up-regulation and the extrinsic apoptosis pathway through caspase-8 down-regulation.     

Genome-wide CRISPR screen identifies synthetic lethality between DOCK1 inhibition and metformin in liver cancer

Metformin is currently a strong candidate anti-tumor agent in multiple cancers. However, its anti-tumor effectiveness varies among different cancers or subpopulations, potentially due to tumor heterogeneity. It thus remains unclear which hepatocellular carcinoma (HCC) patient subpopulation(s) can benefit from metformin treatment. Here, through a genome-wide CRISPR-Cas9-based knockout screen, we find that DOCK1 levels determine the anti-tumor effects of metformin and that DOCK1 is a synthetic lethal target of metformin in HCC. Mechanistically, metformin promotes DOCK1 phosphorylation, which activates RAC1 to facilitate cell survival, leading to metformin resistance. The DOCK1-selective inhibitor, TBOPP, potentiates anti-tumor activity by metformin in vitro in liver cancer cell lines and patient-derived HCC organoids, and in vivo in xenografted liver cancer cells and immunocompetent mouse liver cancer models. Notably, metformin improves overall survival of HCC patients with low DOCK1 levels but not among patients with high DOCK1 expression. This study shows that metformin effectiveness depends on DOCK1 levels and that combining metformin with DOCK1 inhibition may provide a promising personalized therapeutic strategy for metformin-resistant HCC patients.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13238-022-00906-6.     

Combined Treatment with Exendin-4 and Metformin Attenuates Prostate Cancer Growth

Introduction

Recently, the pleiotropic benefits of incretin-based therapy have been reported. We have previously reported that Exendin–4, a glucagon-like peptide–1 (GLP–1) receptor agonist, attenuates prostate cancer growth. Metformin is known for its anti-cancer effect. Here, we examined the anti-cancer effect of Exendin–4 and metformin using a prostate cancer model.

Methods

Prostate cancer cells were treated with Exendin–4 and/or metformin. Cell proliferation was quantified by growth curves and 5-bromo–2′-deoxyuridine (BrdU) assay. TUNEL assay and AMP-activated protein kinase (AMPK) phosphorylation were examined in LNCaP cells. For in vivo experiments, LNCaP cells were transplanted subcutaneously into the flank region of athymic mice, which were then treated with Exendin–4 and/or metformin. TUNEL assay and immunohistochemistry were performed on tumors.

Results

Exendin–4 and metformin additively decreased the growth curve, but not the migration, of prostate cancer cells. The BrdU assay revealed that both Exendin–4 and metformin significantly decreased prostate cancer cell proliferation. Furthermore, metformin, but not Exendin–4, activated AMPK and induced apoptosis in LNCaP cells. The anti-proliferative effect of metformin was abolished by inhibition or knock down of AMPK. In vivo, Exendin–4 and metformin significantly decreased tumor size, and further significant tumor size reduction was observed after combined treatment. Immunohistochemistry on tumors revealed that the P504S and Ki67 expression decreased by Exendin–4 and/or metformin, and that metformin increased phospho-AMPK expression and the apoptotic cell number.

Conclusion

These data suggest that Exendin–4 and metformin attenuated prostate cancer growth by inhibiting proliferation, and that metformin inhibited proliferation by inducing apoptosis. Combined treatment with Exendin–4 and metformin attenuated prostate cancer growth more than separate treatments.     

The Herbal Compound Cryptotanshinone Restores Sensitivity in Cancer Cells That Are Resistant to the Tumor Necrosis Factor-related Apoptosis-inducing Ligand

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) selectively induces apoptosis and kills cancer cells but not normal cells. However, TRAIL resistance due to low level of TRAIL receptor expression is widely found in cancer cells and hampers its development for cancer treatment. Thus, the agents that can sensitize the tumor cells to TRAIL-mediated apoptosis are urgently needed. We investigated whether tanshinones, the major bioactive compounds of Salvia miltiorrhiza (danshen), can up-regulate TRAIL receptor expression. Among the major tanshinones being tested, cryptotanshinone (CT) showed the best ability to induce TRAIL receptor 2 (DR5) expression. We further showed that CT was capable of promoting TRAIL-induced cell death and apoptosis in A375 melanoma cells. CT-induced DR5 induction was not cell type-specific, as DR5 induction was observed in other cancer cell types. DR5 knockdown abolished the enhancing effect of CT on TRAIL responses. Mechanistically, induction of the DR5 by CT was found to be p53-independent but dependent on the induction of CCAAT/enhancer-binding protein-homologous protein (CHOP). Knockdown of CHOP abolished CT-induced DR5 expression and the associated potentiation of TRAIL-mediated cell death. In addition, CT-induced ROS production preceded up-regulation of CHOP and DR5 and consequent sensitization of cells to TRAIL. Interestingly, CT also converted TRAIL-resistant lung A549 cancer cells into TRAIL-sensitive cells. Taken together, our results indicate that CT can potentiate TRAIL-induced apoptosis through up-regulation of DR5.     

Metformin targets Stat3 to inhibit cell growth and induce apoptosis in triple-negative breast cancers

A distinct group of breast cancers, called “basal” or “triple-negative” (TN) cancers express both basal cytokeratins and the epidermal growth factor receptor, but fail to express estrogen receptors, progesterone receptors or HER2 and have stem-like or mesenchymal features. They are particularly aggressive, are frequently chemo-resistant, with p53 mutation, up-regulation of IL-6 and Stat3. Because TN cells are particularly sensitive to the anti-diabetic agent metformin, we hypothesized that it may target JAK2/Stat3 signaling. The effects of metformin upon Stat3 expression and activation were examined in four human TN cell lines. Metformin’s effects were also studied in sublines with forced over-expression of constitutively active (CA) Stat3, as well as lines with stable knockdown of Stat3. Metformin inhibited Stat3 activation (P-Stat3) at Tyr705 and Ser727 and downstream signaling in each of the four parental cell lines. CA-Stat3 transfection attenuated, whereas Stat3 knockdown enhanced, the effects of metformin upon growth inhibition and apoptosis induction. A Stat3 specific inhibitor acted synergistically with metformin in reducing cell growth and inducing apoptosis. An mTOR inhibitor showed no significant interaction with metformin. In summary, Stat3 is a critical regulator of metformin action in TN cancer cells, providing the potential for enhancing metformin’s efficacy in the clinical setting.     

MiR-221/222 promote chemoresistance to cisplatin in ovarian cancer cells by targeting PTEN/PI3K/AKT signaling pathway

Cisplatin resistance is one of the main limitations in the treatment of ovarian cancer, and its mechanism has not been fully understood. The objectives of this study were to determine the role of miR-221/222 and its underlying mechanism in chemoresistance of ovarian cancer. We demonstrated that miR-221/222 expression levels were higher in A2780/CP cells compared with A2780 S cells. An in vitro cell viability assay showed that downregulation of miR-221/222 sensitized A2780/CP cells to cisplatin-induced cytotoxicity. Moreover, we found that knockdown of miR-221/222 by its specific inhibitors promoted the cisplatin-induced apoptosis in A2780/CP cells. Using bioinformatic analysis and luciferase reporter assay, miR-221/222 were found to directly target PTEN. Moreover, knockdown of miR-221/222 in A2780/CP cells significantly upregulated PTEN and downregulated PI3KCA and p-Akt expression. In conclusion, our results demonstrated that miR-221/222 induced cisplatin resistance by targeting PTEN mediated PI3K/Akt pathway in A2780/CP cells, suggesting that miR-221/222/PTEN/PI3K/Akt may be a promising prognostic and therapeutic target to overcome cisplatin resistance and treat ovarian cancer in the future.