Metformin Mitigates DPP-4 Inhibitor-Induced Breast Cancer Metastasis via Suppression of mTOR Signaling.

The biological influence of antidiabetic drugs on cancer cells and diabetic cancer patients has not yet been completely elucidated. We reported that a dipeptidyl peptidase (DPP)-4 inhibitor accelerates mammary cancer metastasis by inducing epithelial-mesenchymal transition (EMT) through the CXCL12/CXCR4/mTOR axis. Metformin has been shown to inhibit the mTOR signaling pathway. In this study, we investigated whether metformin mitigates breast cancer metastasis induced by a DPP-4 inhibitor via suppression of mTOR signaling. In cultured mouse mammary and human breast cancer cells, metformin suppressed DPP-4 inhibitor KR62436 (KR)-induced EMT and cell migration via suppression of the mTOR pathway associated with AMPK activation. For the in vivo study, metformin intervention was performed in an allograft 4T1 breast cancer model mouse with or without KR. We also analyzed mice transplanted with shRNA-mediated DPP-4 knockdown 4T1 cells. Treatment with metformin inhibited the lung metastasis of DPP-4-deficient 4T1 mammary tumor cells generated by either KR administration or DPP-4 knockdown. Immunostaining of primary tumors indicated that DPP-4 suppression promoted the expression of EMT-inducing transcription factor Snail through activation of the CXCR4-mediated mTOR/p70S6K pathway in an allograft breast cancer model; metformin abolished this alteration. Metformin treatment did not alter DPP-4-deficiency-induced expression of CXCL12 in either plasma or primary tumors. Our findings suggest that metformin may serve as an antimetastatic agent by mitigating the undesirable effects of DPP-4 inhibitors in patients with certain cancers. IMPLICATIONS: Metformin could combat the detrimental effects of DPP-4 inhibitor on breast cancer metastasis via mTOR suppression, suggesting the potential clinical relevance. VISUAL OVERVIEW: http://mcr.aacrjournals.org/content/molcanres/19/1/61/F1.large.jpg.

Deficiency in Dipeptidyl Peptidase-4 Promotes Chemoresistance through the CXCL12/CXCR4/mTOR/TGFß Signaling Pathway in Breast Cancer Cells.

Dipeptidyl peptidase (DPP)-4, a molecular target of DPP-4 inhibitors, which are type 2 diabetes drugs, is expressed in a variety of cell types, tissues and organs. DPP-4 has been shown to be involved in cancer biology, and we have recently shown that a DPP-4 inhibitor promoted the epithelial mesenchymal transition (EMT) in breast cancer cells. The EMT is known to associate with chemotherapy resistance via the induction of ATP-binding cassette (ABC) transporters in cancer cells. Here, we demonstrated that deficiency in DPP-4 promoted chemotherapy resistance via the CXCL12/CXCR4/mTOR axis, activating the TGFß signaling pathway via the expression of ABC transporters. DPP-4 inhibition enhanced ABC transporters in vivo and in vitro. Doxorubicin (DOX) further induced ABC transporters in DPP-4-deficient 4T1 cells, and the induction of ABC transporters was suppressed by either the CXCR4 inhibitor AMD3100, the mTOR inhibitor rapamycin or a neutralizing TGFß (1, 2 and 3) antibody(N-TGFß). Knockdown of snail, an EMT-inducible transcription factor, suppressed ABC transporter levels in DOX-treated DPP-4-deficient 4T1 cells. In an allograft mouse model, however, the effects of DOX in either primary tumor or metastasis were not statistically different between control and DPP-4-kd 4T1. Taken together, our findings suggest that DPP-4 inhibitors potentiate chemotherapy resistance via the induction of ABC transporters by the CXCL12/CXCR4/mTOR/TGFß signaling pathway in breast cancer cells.

Inhibition of Dipeptidyl Peptidase-4 Accelerates Epithelial-Mesenchymal Transition and Breast Cancer Metastasis via the CXCL12/CXCR4/mTOR Axis.

Dipeptidyl peptidase (DPP)-4 is a multifunctional glycoprotein involved in various biological and pathologic processes. DPP-4 has been widely recognized as a therapeutic target for type 2 diabetes mellitus but is also implicated in the development of human malignancies. Here, we show that inhibition of DPP-4 accelerates breast cancer metastasis via induction of CXCL12/CXCR4, which activates mTOR to promote epithelial-mesenchymal transition (EMT). In cultured cells, DPP-4 knockdown induced EMT and cell migration. Treatment with the DPP-4 inhibitor KR62436 (KR) promoted primary tumor growth and lung metastasis in a 4T1 tumor allograft mouse model; DPP-4 knockdown in 4T1 cells displayed similar phenotypes in vivo and in vitro. KR treatment enhanced the levels of CXCL12/CXCR4 and phosphorylated mTOR, which were associated with the induction of EMT in metastatic cancer cells. KR-induced EMT in cancer cells was inhibited by treatment with the CXCR4 inhibitor AMD3100 or the mTOR inhibitor rapamycin, and AMD3100 suppressed KR-induced metastasis in vivo. Our findings suggest that DPP-4 plays a significant role in cancer biology and that inhibition of DPP-4 promotes cancer metastasis via induction of the CXCL12/CXCR4/mTOR/EMT axis. SIGNIFICANCE: These findings reveal that inhibition of DPP-4 increases the metastatic potential of breast cancer. This is especially important given the potential use of DPP-4 inhibition as a therapeutic strategy for type 2 diabetes.

AMP-Activated Protein (AMPK) in Pathophysiology of Pregnancy Complications.

Although the global maternal mortality ratio has been consistently reduced over time, in 2015, there were still 303,000 maternal deaths throughout the world, of which 99% occurred in developing countries. Understanding pathophysiology of pregnancy complications contributes to the proper prenatal care for the reduction of prenatal, perinatal and neonatal mortality and morbidity ratio. In this review, we focus on AMP-activated protein kinase (AMPK) as a regulator of pregnancy complications. AMPK is a serine/threonine kinase that is conserved within eukaryotes. It regulates the cellular and whole-body energy homeostasis under stress condition. The functions of AMPK are diverse, and the dysregulation of AMPK is known to correlate with many disorders such as cardiovascular disease, diabetes, inflammatory disease, and cancer. During pregnancy, AMPK is necessary for the proper placental differentiation, nutrient transportation, maternal and fetal energy homeostasis, and protection of the fetal membrane. Activators of AMPK such as 5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR), resveratrol, and metformin restores pregnancy complications such as gestational diabetes mellitus (GDM), preeclampsia, intrauterine growth restriction, and preterm birth preclinically. We also discuss on the relationship between catechol-O-methyltransferase (COMT), an enzyme that metabolizes catechol, and AMPK during pregnancy. It is known that metformin cannot activate AMPK in COMT deficient mice, and that 2-methoxyestradiol (2-ME), a metabolite of COMT, recovers the AMPK activity, suggesting that COMT is a regulator of AMPK. These reports suggest the therapeutic use of AMPK activators for various pregnancy complications, however, careful analysis is required for the safe use of AMPK activators since AMPK activation could cause fetal malformation.

Occurrence of Potentially Lethal Arrhythmia due to Sudden Exposure of an Overt Accessory Pathway 8 Years After Catheter Ablation of a Concealed Accessory Pathway.

Although the efficacy of catheter ablation of the accessory pathway (AP) has been established, there are subgroups of APs with an intermittent conduction property, which is sometimes difficult to diagnose accurately. A 57-year-old man with a history of catheter ablation was referred to our clinic due to frequent faintness. He had undergone concealed AP ablation 8 years previously and bilateral circumferential pulmonary vein isolation (CPVI) 6 years previously. During regular electrocardiogram monitoring, it was suggested that irregular wide QRS tachycardia, which was considered to be atrial fibrillation with antegrade AP conduction, was the cause of the present symptoms. In the present electrophysiological study, we noticed a residual antegrade AP in the left lateral wall that was not observed during the previous session. We achieved abolition of overt accessory conduction, bilateral CPVI, and superior vena cava isolation with several radiofrequency applications without any recurrence. We also confirmed the absence of dormant conduction in the AP and the left atrium-PV connection with 20 mg adenosine triphosphate. This case demonstrated the possibility of sudden exposure of overt AP conduction late after catheter ablation of the concealed AP and the importance of confirming the absence of dormant conduction by means of adenosine triphosphate, which has the potential benefit of revealing latent AP conduction.

Interesting electrophysiological findings in a patient with coexistence of atrial tachycardia originating from coronary sinus and slow-fast atrioventricular nodal reentrant tachycardia.

Slow-fast atrioventricular nodal tachycardia (AVNRT) has various electrophysiological aspects due to atrioventricular (AV) nodal physiology. In addition, concomitantly another form of arrhythmia with AVNRT, especially atrial tachycardia (AT), was an infrequent arrhythmia. A 38-year-old female with narrow QRS tachycardia underwent electrophysiological study due to frequent faintness. The electrophysiological study disclosed the coexistence of AT originating from coronary sinus (CS) with slow-fast AVNRT. We easily diagnosed AT originating from CS and terminated with several radiofrequency ablations (RFA) around CS. The diagnosis of slow-fast AVNRT, however, was somewhat difficult due to the following findings: (1) small amount of adenosine triphosphate (ATP) could terminate slow-fast AVNRT reproducibly; (2) we could provoke slow-fast AVNRT only by RV pacing with isoproterenol infusion. With other electrophysiological findings, we diagnosed slow-fast AVNRT. Radiofrequency energy was delivered initially in the posteroseptal region, followed by inside CS, and finally in the middle septal region, which completed the slow pathway ablation. After the procedure, we could never provoke these arrhythmias. .

Primary Multiple Cardiac Myxomas in a Patient without the Carney Complex.

Cardiac tumors are rare, and multiple myxomas are even rarer. The latter phenomenon is mostly associated with the Carney complex, a dominantly inherited disease characterized by multiple primary cardiac myxomas, endocrinopathy, and spotty pigmentation of the skin. We report the rare case of a patient who did not have the Carney complex but had multiple primary cardiac tumors. A 78-year-old woman with a past history of breast cancer was referred to our hospital for further examination of multiple cardiac tumors. Echocardiography showed 4 tumors in the left atrium and left ventricle. We could not diagnose them preoperatively and decided to resect them surgically because they were mobile and could have caused embolism and obstruction. The postoperative pathological findings of all 4 tumors were myxomas, although the patient did not meet the diagnostic criteria of the Carney complex. Therefore, a rare case of multiple primary cardiac myxomas was diagnosed.

Haematopoietic cells produce BDNF and regulate appetite upon migration to the hypothalamus.

Brain-derived neurotrophic factor (BDNF) suppresses food intake by acting on neurons in the hypothalamus. Here we show that BDNF-producing haematopoietic cells control appetite and energy balance by migrating to the hypothalamic paraventricular nucleus. These haematopoietic-derived paraventricular nucleus cells produce microglial markers and make direct contacts with neurons in response to feeding status. Mice with congenital BDNF deficiency, specifically in haematopoietic cells, develop hyperphagia, obesity and insulin resistance. These abnormalities are ameliorated by bone marrow transplantation with wild-type bone marrow cells. Furthermore, when injected into the third ventricle, wild-type bone marrow mononuclear cells home to the paraventricular nucleus and reverse the hyperphagia of BDNF-deficient mice. Our results suggest a novel mechanism of feeding control based on the production of BDNF by haematopoietic cells and highlight a potential new therapeutic route for the treatment of obesity.

p53 upregulation is a frequent response to deficiency of cell-essential genes.

BACKGROUND: The role of p53 in the prevention of development of embryos damaged by genotoxic factors is well recognized. However, whether p53 plays an analogous role in preventing birth defects from genetic mutations remains an unanswered question. Genetic screens for mutations affecting development show that only a fraction of developmentally lethal mutations leads to specific phenotypes while the majority results in similar recurrent phenotypes characterized by neuronal apoptosis and developmental delay. Mutations in cell-essential genes typically fall into this group. The observation that mutations in diverse housekeeping genes lead to a similar phenotype suggests a common mechanism underlying this phenotype. For some mutants, p53 inhibition was shown to attenuate the phenotype. METHODOLOGY/PRINCIPAL FINDINGS: To find out how common p53 involvement is in this phenotype, we analyzed zebrafish mutants from various categories of cell essential genes. Several thousand zebrafish mutants have been identified; many of them are kept at stock centers and available for the research community. We selected mutants for genes functioning in DNA replication, transcription, telomere maintenance, ribosome biogenesis, splicing, chaperoning, endocytosis, and cellular transport. We found that mutants have similar phenotypes including neural apoptosis, failure to develop structures originated from the neural crest cells, and hematopoietic defects. All mutants share p53 upregulation and similar changes in several p53-dependent and independent molecular pathways. CONCLUSION/SIGNIFICANCE: Our results suggest that mutations in housekeeping genes often canalize on the p53-mediated phenotype. p53 prevents the development of embryos with defects in such genes. p53-mediated changes in gene expression may also contribute to many human congenital malformations.