Targeting of PP2Cδ By a Small Molecule C23 Inhibits High Glucose-Induced Breast Cancer Progression In Vivo

Antiproliferative effect of ketogenic diet on hormone independent mammary gland carcinoma via harnessing glucose metabolism: In-vitro and In-vivo investigations

The ketogenic diet (KD) has been emphasized as a complementary strategy for management of several clinical conditions including cancer. Therefore, in this study we explored the effect of KD in mammary gland carcinoma through in-vitro and in-vivo studies. In-vitro studies were performed on MCF-7 and MDA-MB-231 cells with different experimental conditions such as high glucose (HG), low glucose (LG) and no glucose(NG) in conjugation with β-hydroxy butyrate(BHB) treatment. The MTT assay revealed that glucose deprivation alongwith BHB(10 mM) treatment significantly reduces the viability of MDA-MB-231 cells as compared to MCF-7 cells. Moreover, apoptotic and antiproliferative potential (via AO/EtBr, JC-1, cell migration assay) were analyzed on MDA-MB-231 cells which indicate that NG with BHB treatment induce cell death.Furthermore, we investigated the in-vivo anticancer efficacy against DMBA-induced mammary gland carcinoma in female Wistar rats. KD treatment effectively restored autonomic dysfunction, altered mammary gland morphology and histology; as evident through decrease in lobules, alveolar bud, restoration of the surface architecture and loss of tumor micro-vessels. The altered levels of antioxidants such as TBARs(0.85 ± 0.19 nM of MDA/µg of protein), SOD(2.26 ± 0.05 U/µg of protein), PC(41.36 ± 2.94 µM/µg of protein), GSH(10.58 ± 3.08 µM/µg of protein) were also restored after KD treatment. Overall findings suggested, that deprived glucose concentration alongwith BHB can impart antiproliferative and apoptotic effect as observed through MDA-MB-231cells. Moreover, KD also diminished the carcinogenic effects of DMBA in albino wistar rats. In view of above, the KD was utilised as adjuvant therapy in the management of mammary gland carcinoma,possibly by providing unfavourable microenvironment for highly proliferating tumour cells due deficiency of quickly available glucose.

Wip1 phosphatase activator QGC-8-52 specifically sensitizes p53-negative cancer cells to chemotherapy while protecting normal cells

PP2C serine-threonine phosphatase Wip1 plays an important role in normal tissue homeostasis, stress signaling and pathogenesis of various human diseases. It is an attractive drug target for cancer treatment and inhibition of its expression or activity constitute a novel therapeutic intervention strategy to prevent the development of various cancers. However, previous strategies for Wip1 suppression may be ineffective in cancers lacking p53. Here, we have characterized the activity of a novel Wip1 phosphatase activator, QGC-8-52, in preclinical models of breast malignancies. QGC-8-52 significantly sensitizes the cancer cell lines with p53 deletion to chemotherapeutic agents. This effect was mediated by the Wip1-FOXO3a interaction and subsequent dephosphorylation of Thr487 that resulted, in response to anticancer treatment, in enhancing the transcription activity of FOXO3a on the proapoptotic TRAIL gene. The sensitizing effect of Wip1 activation on chemotherapeutic drugs only targeted cancer cells lacking p53. The activation of Wip1 in normal cells provided protection from anticancer drug-induced apoptosis by reducing the strength of upstream signaling to p53. Therefore, during the treatment of anticancer drugs, the activated Wip1 phosphatase boosts the apoptosis of p53-negative tumors and protects normal tissues. Our findings may represent an effective and safe therapeutic strategy for cancers with p53 deletion.

Oxidatively Damaged Nucleic Acid: Linking Diabetes and Cancer

Significance: Our current knowledge of the mechanism between diabetes and cancer is limited. Oxidatively damaged nucleic acid is considered a critical factor to explore the connections between these two diseases. Recent Advances: The link between diabetes mellitus and cancer has attracted increasing attention in recent years. Emerging evidence supports that oxidatively damaged nucleic acid caused by an imbalance between reactive oxygen species generation and elimination is a bridge connecting diabetes and cancer. 8-Oxo-7,8-dihydro-2'-deoxyguanosine and 8-oxo-7,8-dihydroguanosine assume important roles as biomarkers in assessing the relationship between oxidatively damaged nucleic acid and cancer. Critical Issues: The consequences of diabetes are extensive and may lead to the occurrence of cancer by influencing a combination of factors. At present, there is no direct evidence that diabetes causes cancer by affecting a single factor. Furthermore, the difficulty in controlling variables and differences in detection methods lead to poor reliability and repeatability of results, and there are no clear cutoff values for biomarkers to indicate cancer risk. Future Directions: A better understanding of connections as well as mechanisms between diabetes and cancer is still needed. Both diabetes and cancer are currently intractable diseases. Further exploration of the specific mechanism of oxidatively damaged nucleic acid in the connection between diabetes and cancer is urgently needed. In the future, it is necessary to further take oxidatively damaged nucleic acid as an entry point to provide new ideas for the diagnosis and treatment of diabetes and cancer. Experimental drugs targeting the repair process of oxidatively generated damage require an extensive preclinical evaluation and could ultimately provide new treatment strategies for these diseases. Antioxid. Redox Signal. 37, 1153-1167.

Allosteric inhibition of PPM1D serine/threonine phosphatase via an altered conformational state

PPM1D encodes a serine/threonine phosphatase that regulates numerous pathways including the DNA damage response and p53. Activating mutations and amplification of PPM1D are found across numerous cancer types. GSK2830371 is a potent and selective allosteric inhibitor of PPM1D, but its mechanism of binding and inhibition of catalytic activity are unknown. Here we use computational, biochemical and functional genetic studies to elucidate the molecular basis of GSK2830371 activity. These data confirm that GSK2830371 binds an allosteric site of PPM1D with high affinity. By further incorporating data from hydrogen deuterium exchange mass spectrometry and sedimentation velocity analytical ultracentrifugation, we demonstrate that PPM1D exists in an equilibrium between two conformations that are defined by the movement of the flap domain, which is required for substrate recognition. A hinge region was identified that is critical for switching between the two conformations and was directly implicated in the high-affinity binding of GSK2830371 to PPM1D. We propose that the two conformations represent active and inactive forms of the protein reflected by the position of the flap, and that binding of GSK2830371 shifts the equilibrium to the inactive form. Finally, we found that C-terminal truncating mutations proximal to residue 400 result in destabilization of the protein via loss of a stabilizing N- and C-terminal interaction, consistent with the observation from human genetic data that nearly all PPM1D mutations in cancer are truncating and occur distal to residue 400. Taken together, our findings elucidate the mechanism by which binding of a small molecule to an allosteric site of PPM1D inhibits its activity and provides insights into the biology of PPM1D.

A Novel Metabolic Reprogramming Strategy for the Treatment of Diabetes-Associated Breast Cancer

Diabetes is directly related to the risk of breast cancer (BC) occurrence and worsened BC prognosis. Currently, there are no specific treatments for diabetes-associated BC. This paper aims to understand the fundamental mechanisms of diabetes-induced BC progression and to develop personalized treatments. It reports a metabolic reprogramming strategy (MRS) that pharmaceutical induction of glucose import and glycolysis with metformin and NF-κB inhibitor (NF-κBi) while blocking the export of excessive lactate via inhibiting monocarboxylate transporter 4 (MCT4) leads to a metabolic crisis within the cancer cells. It demonstrates that the MRS shifts the metabolism of BC cells toward higher production of lactate, blocks lactate secretion, prompts intracellular acidification and induces significant cytotoxicity. Moreover, a novel MCT4 inhibitor CB-2 has been identified by structure-based virtual screening. A triple combination of metformin, CB-2, and trabectedin, a drug that impedes NF-κB signaling, strongly inhibits BC cells. Compared to normal glucose condition, MRS elicits more potent cancer cell-killing effects under high glucose condition. Animal model studies show that diabetic conditions promote the proliferation and progression of BC xenografts in nude mice and that MRS treatment significantly inhibits HG-induced BC progression. Therefore, inhibition of MCT4 combined with metformin/NF-κBi is a promising cancer therapy, especially for diabetes-associated BC.

High glucose: an emerging association between diabetes mellitus and cancer progression

The association of cancer and diabetes mellitus (DM) has been studied for decades. Hyperglycemia and the imbalance of hormones are factors that contribute to the molecular link between DM and carcinogenesis and cancer progression. Hyperglycemia alone or in combination with hyperinsulinemia are key factors that promote cancer aggressiveness. Many preclinical studies suggest that high glucose induces abnormal energy metabolism and aggressive cancer via several mechanisms. As evidenced by clinical studies, hyperglycemia is associated with poor clinical outcomes in patients who have comorbid DM. The prognoses of cancer patients with DM are improved when their plasma glucose levels are controlled. This suggests that high glucose level maybe be involved in the molecular mechanism that causes the link between DM and cancer and may also be useful for prognosis of cancer progression. This review comprehensively summarizes the evidence from recent pre-clinical and clinical studies of the impact of hyperglycemia on cancer advancement as well as the underlying molecular mechanism for this impact. Awareness among clinicians of the association between hyperglycemia or DM and cancer progression may improve cancer treatment outcome in patients who have DM.

Ginsenoside Rh1 Induces MCF-7 Cell Apoptosis and Autophagic Cell Death through ROS-Mediated Akt Signaling

Simple Summary

Breast cancer (BC) is the most common cause of cancer-related deaths among women worldwide, and its incidence has been increasing. However, current therapeutic approaches, such as chemotherapy, radiation, and hormonal therapy, have become increasingly ineffective because of their severe adverse effects and multidrug resistance. Therefore, the discovery of new potential candidates for BC therapy is essential. Here, we investigated whether ginsenoside Rh1 exhibits anticancer effects on BC. We found that this ginsenoside effectively inhibited the growth of BC cells in both cell cultures and mice. Therefore, ginsenoside Rh1 is a promising candidate for BC treatment.

Abstract

Breast cancer (BC) is the leading cause of cancer-related deaths among women worldwide. Ginsenosides exhibit anticancer activity against various cancer cells. However, the effects of ginsenoside Rh1 on BC and the underlying mechanisms remain unknown. Here, we investigated the anticancer effects of Rh1 on human BC MCF-7 and HCC1428 cells and the underlying signaling pathways. The anticancer effects of Rh1 in vitro were evaluated using sulforhodamine B (SRB), 3-(4, 5-dimethylthiazole-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), clonogenic assay, propidium iodide (PI)/Hoechst staining, Western blotting, flow cytometry, and immunofluorescence analysis. The in vivo effects of Rh1 were determined using a xenograft model via hematoxylin and eosin and the immunohistochemistry staining of tumor tissues. We found that Rh1 exerted cytotoxicity in the cells by increasing cell apoptosis, autophagy, and cell cycle arrest. These effects were further enhanced by a phosphatidylinositol 3-kinase (PI3K) inhibitor but were rescued by the inhibition of reactive oxygen species (ROS). Moreover, enhanced ROS generation by Rh1 inhibited the activation of the PI3K/Akt pathway. Consistently, Rh1 treatment significantly reduced tumor growth in vivo and increased the ROS production and protein expression of LC3B and cleaved caspase-3 but decreased the phosphorylation of Akt and retinoblastoma (Rb) in tumor tissues. Taken together, Rh1 exerted a potential anticancer effect on BC cells by inducing cell cycle arrest, apoptosis, and autophagy via inhibition of the ROS-mediated PI3K/Akt pathway.

Comp34 displays potent preclinical antitumor efficacy in triple-negative breast cancer via inhibition of NUDT3-AS4, a novel oncogenic long noncoding RNA

The abnormal PI3K/AKT/mTOR pathway is one of the most common genomic abnormalities in breast cancers including triple-negative breast cancer (TNBC), and pharmacologic inhibition of these aberrations has shown activity in TNBC patients. Here, we designed and identified a small-molecule Comp34 that suppresses both AKT and mTOR protein expression and exhibits robust cytotoxicity towards TNBC cells but not nontumorigenic normal breast epithelial cells. Mechanically, long noncoding RNA (lncRNA) AL354740.1-204 (also named as NUDT3-AS4) acts as a microRNA sponge to compete with AKT1/mTOR mRNAs for binding to miR-99s, leading to decrease in degradation of AKT1/mTOR mRNAs and subsequent increase in AKT1/mTOR protein expression. Inhibition of lncRNA-NUDT3-AS4 and suppression of the NUDT3-AS4/miR-99s association contribute to Comp34-affected biologic pathways. In addition, Comp34 alone is effective in cells with secondary resistance to rapamycin, the best-known inhibitor of mTOR, and displays a greater in vivo antitumor efficacy and lower toxicity than rapamycin in TNBC xenografted models. In conclusion, NUDT3-AS4 may play a proproliferative role in TNBC and be considered a relevant therapeutic target, and Comp34 presents promising activity as a single agent to inhibit TNBC through regulation of NUDT3-AS4 and miR-99s.

Could ketogenic diet "starve" cancer? Emerging evidence

Cancer cells (CCs) predominantly use aerobic glycolysis (Warburg effect) for their metabolism. This important characteristic of CCs represents a potential metabolic pathway to be targeted in the context of tumor treatment. Being this mechanism related to nutrient oxidation, dietary manipulation has been hypothesized as an important strategy during tumor treatment. Ketogenic diet (KD) is a dietary pattern characterized by high fat intake, moderate-to-low protein consumption, and very-low-carbohydrate intake (<50 g), which in cancer setting may target CCs metabolism, potentially influencing both tumor treatment and prognosis. Several mechanisms, far beyond the originally proposed inhibition of glucose/insulin signaling, can underpin the effectiveness of KD in cancer management, ranging from oxidative stress, mitochondrial metabolism, and inflammation. The role of a qualified Nutritionist is essential to reduce and manage the short and long-term complications of this dietary therapy, which must be personalized to the individual patient for the planning of tailored KD protocol in cancer patients. In the present review, we summarize the proposed antitumor mechanisms of KD, the application of KD in cancer patients with obesity and cachexia, and the preclinical and clinical evidence on KD therapy in cancer.

Advanced glycation end products in diabetes, cancer and phytochemical therapy

The irreversible glycation and oxidation of proteins and lipids produces advanced glycation end products (AGEs). These modified AGEs are triggered to bind the receptor for AGE (RAGE), thereby activating its downstream signaling pathways, such as nuclear factor (NF)-κB and phosphoinositide 3-kinase (PI3K)/Akt, ultimately leading to diabetes and cancers. In this review, we focus on the interaction of AGE-RAGE and their associated pathways. We also consider the activity of phytochemicals, such as genistein and curcumin, that trap dicarbonyl compounds including methylglyoxal (MG) and glyoxalase that arise from multiple pathways to block AGE formation and prevent its interaction with RAGE.

The role of PPM1D in cancer and advances in studies of its inhibitors

A greater understanding of factors causing cancer initiation, progression and evolution is of paramount importance. Among them, the serine/threonine phosphatase PPM1D, also referred to as wild-type p53-induced phosphatase 1 (Wip1) or protein phosphatase 2C delta (PP2Cδ), is emerging as an important oncoprotein due to its negative regulation on a number of crucial cancer suppressor pathways. Initially identified as a p53-regulated gene, PPM1D has been afterwards found amplified and more recently mutated in many human cancers such as breast cancer. The latest progress in this field further reveals that selective inhibition of PPM1D to delay tumor onset or reduce tumor burden represents a promising anti-cancer strategy. Here, we review the advances in the studies of the PPM1D activity and its relevance to various cancers, and recent progress in development of PPM1D inhibitors and discuss their potential application in cancer therapy. Consecutive research on PPM1D and its relationship with cancer is essential, as it ultimately contributes to the etiology and treatment of cancer.

Consideration of Ketogenic Metabolic Therapy as a Complementary or Alternative Approach for Managing Breast Cancer

Breast cancer remains as a significant cause of morbidity and mortality in women. Ultrastructural and biochemical evidence from breast biopsy tissue and cancer cells shows mitochondrial abnormalities that are incompatible with energy production through oxidative phosphorylation (OxPhos). Consequently, breast cancer, like most cancers, will become more reliant on substrate level phosphorylation (fermentation) than on oxidative phosphorylation (OxPhos) for growth consistent with the mitochondrial metabolic theory of cancer. Glucose and glutamine are the prime fermentable fuels that underlie therapy resistance and drive breast cancer growth through substrate level phosphorylation (SLP) in both the cytoplasm (Warburg effect) and the mitochondria (Q-effect), respectively. Emerging evidence indicates that ketogenic metabolic therapy (KMT) can reduce glucose availability to tumor cells while simultaneously elevating ketone bodies, a non-fermentable metabolic fuel. It is suggested that KMT would be most effective when used together with glutamine targeting. Information is reviewed for suggesting how KMT could reduce systemic inflammation and target tumor cells without causing damage to normal cells. Implementation of KMT in the clinic could improve progression free and overall survival for patients with breast cancer.

PP2Cδ inhibits p300-mediated p53 acetylation via ATM/BRCA1 pathway to impede DNA damage response in breast cancer

Although nuclear type 2C protein phosphatase (PP2Cδ) has been demonstrated to be pro-oncogenic with an important role in tumorigenesis, the underlying mechanisms that link aberrant PP2Cδ levels with cancer development remain elusive. Here, we found that aberrant PP2Cδ activity decreases p53 acetylation and its transcriptional activity and suppresses doxorubicin-induced cell apoptosis. Mechanistically, we show that BRCA1 facilitates p300-mediated p53 acetylation by complexing with these two proteins and that S1423/1524 phosphorylation is indispensable for this regulatory process. PP2Cδ, via dephosphorylation of ATM, suppresses DNA damage-induced BRCA1 phosphorylation, leading to inhibition of p300-mediated p53 acetylation. Furthermore, PP2Cδ levels correlate with histological grade and are inversely associated with BRCA1 phosphorylation and p53 acetylation in breast cancer specimens. C23, our newly developed PP2Cδ inhibitor, promotes the anticancer effect of doxorubicin in MCF-7 xenograft-bearing nude mice. Together, our data indicate that PP2Cδ impairs p53 acetylation and DNA damage response by compromising BRCA1 function.