OSI-027 inhibits pancreatic ductal adenocarcinoma cell proliferation and enhances the therapeutic effect of gemcitabine both in vitro and in vivo

Roles of Rictor alterations in gastrointestinal tumors (Review)

Gastrointestinal tumors account for five of the top 10 causes of mortality from all cancers (colorectal, liver, stomach, esophageal and pancreatic cancer). Mammalian target of rapamycin (mTOR) signaling is commonly dysregulated in various human cancers. As a core component of the mTOR complex 2 (mTORC2), Rictor is a key effector molecule of the PI3K/Akt pathway. A high alteration rate of Rictor has been observed in gastrointestinal tumors, and such Rictor alterations are often associated with resistance to chemotherapy and related adverse clinical outcomes. However, the exact roles of Rictor in gastrointestinal tumors remain elusive. The aim of the present study was to critically discuss the following: i) Mutation and biological characteristics of Rictor in tumors with a detailed overview of Rictor in cell proliferation, angiogenesis, apoptosis, autophagy and drug resistance; ii) the role of Rictor in tumors of the digestive system, particularly colorectal, hepatobiliary, gastric, esophageal and pancreatic cancer and cholangiocarcinoma; and iii) the current status and prospects of targeted therapy for Rictor by inhibiting Akt activation. Despite the growing realization of the importance of Rictor/mTORC2 in cancer, the underlying mechanistic details remain poorly understood; this needs to change in order for the development of efficient targeted therapies and re‑sensitization of therapy‑resistant cancers to be made possible.

Multifaceted role of mTOR (mammalian target of rapamycin) signaling pathway in human health and disease

The mammalian target of rapamycin (mTOR) is a protein kinase that controls cellular metabolism, catabolism, immune responses, autophagy, survival, proliferation, and migration, to maintain cellular homeostasis. The mTOR signaling cascade consists of two distinct multi-subunit complexes named mTOR complex 1/2 (mTORC1/2). mTOR catalyzes the phosphorylation of several critical proteins like AKT, protein kinase C, insulin growth factor receptor (IGF-1R), 4E binding protein 1 (4E-BP1), ribosomal protein S6 kinase (S6K), transcription factor EB (TFEB), sterol-responsive element-binding proteins (SREBPs), Lipin-1, and Unc-51-like autophagy-activating kinases. mTOR signaling plays a central role in regulating translation, lipid synthesis, nucleotide synthesis, biogenesis of lysosomes, nutrient sensing, and growth factor signaling. The emerging pieces of evidence have revealed that the constitutive activation of the mTOR pathway due to mutations/amplification/deletion in either mTOR and its complexes (mTORC1 and mTORC2) or upstream targets is responsible for aging, neurological diseases, and human malignancies. Here, we provide the detailed structure of mTOR, its complexes, and the comprehensive role of upstream regulators, as well as downstream effectors of mTOR signaling cascades in the metabolism, biogenesis of biomolecules, immune responses, and autophagy. Additionally, we summarize the potential of long noncoding RNAs (lncRNAs) as an important modulator of mTOR signaling. Importantly, we have highlighted the potential of mTOR signaling in aging, neurological disorders, human cancers, cancer stem cells, and drug resistance. Here, we discuss the developments for the therapeutic targeting of mTOR signaling with improved anticancer efficacy for the benefit of cancer patients in clinics.

Recent advances in PI3K/PKB/mTOR inhibitors as new anticancer agents

The biochemical role of the PI3K/PKB/mTOR signalling pathway in cell-cycle regulation is now well known. During the onset and development of different forms of cancer it becomes overactive reducing apoptosis and allowing cell proliferation. Therefore, this pathway has become an important target for the treatment of various forms of malignant tumors, including breast cancer and follicular lymphoma. Recently, several more or less selective inhibitors targeting these proteins have been identified. In general, drugs that act on multiple targets within the entire pathway are more efficient than single targeting inhibitors. Multiple inhibitors exhibit high potency and limited drug resistance, resulting in promising anticancer agents. In this context, the present survey focuses on small molecule drugs capable of modulating the PI3K/PKB/mTOR signalling pathway, thus representing drugs or drug candidates to be used in the pharmacological treatment of different forms of cancer.

Functional stratification of cancer drugs through integrated network similarity

Drugs not only perturb their immediate protein targets but also modulate multiple signaling pathways. In this study, we explored networks modulated by several drugs across multiple cancer cell lines by integrating their targets with transcriptomic and phosphoproteomic data. As a result, we obtained 236 reconstructed networks covering five cell lines and 70 drugs. A rigorous topological and pathway analysis showed that chemically and functionally different drugs may modulate overlapping networks. Additionally, we revealed a set of tumor-specific hidden pathways with the help of drug network models that are not detectable from the initial data. The difference in the target selectivity of the drugs leads to disjoint networks despite sharing a similar mechanism of action, e.g., HDAC inhibitors. We also used the reconstructed network models to study potential drug combinations based on the topological separation and found literature evidence for a set of drug pairs. Overall, network-level exploration of drug-modulated pathways and their deep comparison may potentially help optimize treatment strategies and suggest new drug combinations.

Combating TKI resistance in CML by inhibiting the PI3K/Akt/mTOR pathway in combination with TKIs: a review

Chronic myeloid leukemia (CML), a myeloproliferative hematopoietic cancer, is caused by a genetic translocation between chromosomes 9 and 22. This translocation produces a small Philadelphia chromosome, which contains the Bcr-Abl oncogene. The Bcr-Abl oncogene encodes the BCR-ABL protein, upregulates various signaling pathways (JAK-STAT, MAPK/ERK, and PI3K/Akt/mTOR), and out of which the specifically highly active pathway is the PI3K/Akt/mTOR pathway. Among early treatments for CML, tyrosine kinase inhibitors (TKIs) were found to be the most effective, but drug resistance against kinase inhibitors led to the discovery of novel alternative therapies. At this point, the PI3K/Akt/mTOR pathway components became new targets due to stimulation of this pathway in TKIs-resistant CML patients. The current review article deals with reviewing the scientific literature on the PI3K/Akt/mTOR pathway inhibitors listed in the National Cancer Institute (NCI) drug dictionary and proved effective against multiple cancers. And out of those enlisted inhibitors, the US FDA has also approved some PI3K inhibitors (Idelalisib, Copanlisib, and Duvelisib) and mTOR inhibitors (Everolimus, Sirolimus, and Temsirolimus) for cancer therapy. So far, several inhibitors have been tested, and further investigations are still ongoing. Even in Imatinib, Nilotinib, and Ponatinib-resistant CML cells, a dual PI3K/mTOR inhibitor, BEZ235, showed antiproliferative activity. Therefore, by considering the literature data of these reviews and further examining some of the reported inhibitors, which proved effective against the PI3K/Akt/mTOR signaling pathway in multiple cancers, may improve the therapeutic approaches towards TKI-resistant CML cells where the respective signaling pathway gets upregulated.

Research progress of mTOR inhibitors

Mammalian target of rapamycin (mTOR) is a highly conserved Serine/Threonine (Ser/Thr) protein kinase, which belongs to phosphatidylinositol-3-kinase-related kinase (PIKK) protein family. mTOR exists as two types of protein complex: mTORC1 and mTORC2, which act as central controller regulating processes of cell metabolism, growth, proliferation, survival and autophagy. The mTOR inhibitors block mTOR signaling pathway, producing anti-inflammatory, anti-proliferative, autophagy and apoptosis induction effects, thus mTOR inhibitors are mainly used in cancer therapy. At present, mTOR inhibitors are divided into four categories: Antibiotic allosteric mTOR inhibitors (first generation), ATP-competitive mTOR inhibitors (second generation), mTOR/PI3K dual inhibitors (second generation) and other new mTOR inhibitors (third generation). In this article, these four categories of mTOR inhibitors and their structures, properties and some clinical researches will be introduced. Among them, we focus on the structure of mTOR inhibitors and try to analyze the structure-activity relationship. mTOR inhibitors are classified according to their chemical structure and their contents are introduced systematically. Moreover, some natural products that have direct or indirect mTOR inhibitory activities are introduced together. In this article, we analyzed the target, binding mode and structure-activity relationship of each generation of mTOR inhibitors and proposed two hypothetic scaffolds (the inverted-Y-shape scaffold and the C-shape scaffold) for the second generation of mTOR inhibitors. These findings may provide some help or reference for drug designing, drug modification or the future development of mTOR inhibitor.

Mitochondrial Genome-Derived circRNA mc-COX2 Functions as an Oncogene in Chronic Lymphocytic Leukemia

Circular RNAs (circRNAs), a novel family of non-coding RNAs, play crucial roles in cancer progression. While the existing research focuses on nuclear genome-derived (nu)-circRNAs, the biological and clinical characteristics of mitochondrial genome-derived (mt)-circRNAs remain largely unknown, especially in chronic lymphocytic leukemia (CLL). In this study, we attempted to identify the novel characteristics of mc-COX2 (mitochondrial genome-derived circRNAs [mc]), one of the mt-circRNAs that can be involved in CLL progression. mt-circRNAs were found to be highly expressed in the plasma exosomes of CLL patients. The endogenous reduction of mc-COX2 can affect mitochondrial functions, suppress cell proliferation, and induce cell apoptosis. The upregulation of mc-COX2 was positively associated with leukemogenesis and worsening survival of CLL patients. Notably, functional analysis revealed that mc-COX2, as differing from conventional nu-circRNAs, was less stable and may function through novel mechanisms other than acting as the competing endogenous RNA. We also screened and tested several chemical compounds and small-molecule inhibitors that can decrease the generation of mc-COX2. It was found that the silencing of mc-COX2 in CLL cells strengthened the anti-tumor effects of drugs used in coordination. Our findings prove that mc-COX2, a critical mt-circRNA highly expressed in plasma, derived from CLL cells and delivered by exosomes, is associated with the progression and prognosis of CLL.

The role of RICTOR amplification in targeted therapy and drug resistance

The emergence of tyrosine kinase inhibitors (TKIs) has changed the current treatment paradigm and achieved good results in recent decades. However, an increasing number of studies have indicated that the complex network of receptor tyrosine kinase (RTK) co-activation could influence the characteristic phenotypes of cancer and the tumor response to targeted treatments. One of strategies to blocking RTK co-activation is targeting the downstream factors of RTK, such as PI3K-AKT-mTOR pathway. RICTOR, a core component of mTORC2, acts as a key effector molecule of the PI3K-AKT pathway; its amplification is often associated with poor clinical outcomes and resistance to TKIs. Here, we discuss the biology of RICTOR in tumor and the prospects of targeting RICTOR as a complementary therapy to inhibit RTK co-activation.

High Expression of Long Noncoding RNA HOTAIRM1 is Associated with the Proliferation and Migration in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an incurable malignancy. Long noncoding RNA (LncRNA) HOTAIRM1 (HOX antisense intergenic RNA myeloid 1) has been shown to play important roles in the progression of several type cancers. However, the exact role of HOTAIRM1 in PDAC development remains largely unknown. This study aims to evaluate the potential function of HOTAIRM1 in the development and progress of PDAC. HOTAIRM1 expression was measured by RT-qPCR in forty seven paired human PDAC tissues and five PDAC cell lines. SW1990 and PANC-1 cells were transfected with siHOTAIRM1 to achieve HOTAIRM1 silence. MTT assay and colony formation assay were used to detect the effect of HOTAIRM1 knockdown on cell proliferation. The impact of HOTAIRM1 silence on cell cycle and apoptosis was assessed by flow cytometry assay. Transwell migration assay was performed to explore the influence of HOTAIRM1 downregulation on the migratory potential of PDAC cells. Western blot assay was applied to determine the expression changes of cell cycle, apoptosis, and migration-related genes before and after downregulating HOTAIRM1. HOTAIRM1 expression was abnormally upregulated in PDAC tissues and cells when compared with the control samples, and was positively associated with the expression of KRAS gene mutation. In vitro functional experiments, HOTAIRM1 expression was significantly downregulated by transfection with siHOTAIRM1 in SW1990 and PANC cell lines. HOTAIRM1 knockdown attenuated cell proliferation by inducing cell cycle arrest at G0/G1 phase, promoted cell apoptosis, and inhibited cell migration in PDAC cells by regulating related-genes expression. In conclusion, HOTAIRM1 plays a critical role in PDAC progression, which may be a novel diagnostic and rational therapeutic target for the treatment of pancreatic ductal adenocarcinoma.

Knocking down FAM83B inhibits endometrial cancer cell proliferation and metastasis by silencing the PI3K/AKT/mTOR pathway

Family with sequence similarity 83 member B (FAM83B) has been recently identified as an oncogene involved in the development of various human cancers. However, the role of FAM83B in endometrial cancer tumorigenesis and metastasis is unclear. In this study, we found that the expression of FAM83B was upregulated in endometrial cancer tissues and cell lines. FAM83B expression in endometrial cancer tissues was significantly higher than that in normal tissues and higher FAM83B expression was closely related to poorly survival rate according to TCGA analysis. Moreover, FAM83B expression was correlated with International Federation of Gynecology and Obstetrics (FIGO)stage and myometrial invasion but had no significant correlation with age or histological grade. FAM83B knockdown inhibited endometrial cancer cell proliferation, migration, and invasion arrested the cell cycle at the G1/S stage and promoted apoptosis. FAM83B knockdown also inhibited endometrial cancer growth and lung metastasis in vivo. FAM83B knockdown silenced the PI3K/AKT/mTOR pathway and promoted autophagy. Furthermore, activation of the PI3K/AKT/mTOR pathway reversed FAM83B knockdown-induced autophagy promotion and inhibition of proliferation, migration, and invasion in endometrial cancer cells. Taken together, these results indicate that FAM83B promotes endometrial cancer cell proliferation and metastasis by inhibiting autophagy via activating the PI3K/AKT/mTOR pathway.

Gemcitabine enhances OSI-027 cytotoxicity by upregulation of miR-663a in pancreatic ductal adenocarcinoma cells

Pancreatic ductal adenocarcinoma (PDAC) is well-known to be the most deadly malignancy with the worst survival rate of all cancers. Gemcitabine-based chemotherapy is the most common treatment option for pancreatic ductal adenocarcinoma. However, it offers little therapeutic value in many cases due to the rapid development of chemoresistance. MicroRNAs (miRNAs) have been found to play pivotal roles in the chemotherapeutic resistance of PDAC. In the present study, we examined the molecular basis for the effective combination of OSI-027 and gemcitabine (GEM). Firstly, we identified a specific miRNA expression profile in PDAC cells after treatment with either of these drugs. We found that miR-663a was significantly upregulated after treatment with GEM and downregulated after OSI-027 treatment. With combination of the two drugs, miR-663a level was lower than the GEM group, but higher than the OSI-027 group. Real-time quantitative PCR confirmed these observations. To further establish the role of miR-663a in OSI-027 and GEM resistance in pancreatic cancer, we transfected PDAC cells with miR-663a mimic or miR-663a inhibitor. Cell viability and proliferation assays showed that miR-663a mimic enhanced drug sensitivity, while inhibitor promoted drug resistance. Moreover, we found that the combined effect of OSI-027 and GEM disappeared after inhibiting miR-663a. Our study clearly demonstrates that GEM upregulates miR-663a, thereby promoting the sensitivity of pancreatic cancer cells to OSI-027. Our study suggests that miR-663a expression may be a useful indicator of the potential for chemoresistance and provides a potential new therapeutic target to avert chemoresistance in PDAC.

Mechanisms of autophagy and relevant small-molecule compounds for targeted cancer therapy

Autophagy is an evolutionarily conserved, multi-step lysosomal degradation process for the clearance of damaged or superfluous proteins and organelles. Accumulating studies have recently revealed that autophagy is closely related to a variety of types of cancer; however, elucidation of its Janus role of either tumor-suppressive or tumor-promoting still remains to be discovered. In this review, we focus on summarizing the context-dependent role of autophagy and its complicated molecular mechanisms in different types of cancer. Moreover, we discuss a series of small-molecule compounds targeting autophagy-related proteins or the autophagic process for potential cancer therapy. Taken together, these findings would shed new light on exploiting the intricate mechanisms of autophagy and relevant small-molecule compounds as potential anti-cancer drugs to improve targeted cancer therapy.

Quercetin and doxorubicin co-encapsulated biotin receptor-targeting nanoparticles for minimizing drug resistance in breast cancer

The combination of a chemotherapeutic drug with a chemosensitizer has emerged as a promising strategy for cancers showing multidrug resistance (MDR). Herein we describe the simultaneous targeted delivery of two drugs to tumor cells by using biotin-decorated poly(ethylene glycol)-b-poly(ε-caprolactone) nanoparticles encapsulating the chemotherapeutic drug doxorubicin and the chemosensitizer quercetin (BNDQ). Next, the potential ability of BNDQ to reverse MDR in vitro and in vivo was investigated. Studies demonstrated that BNDQ was more effectively taken up with less efflux by doxorubicin-resistant MCF-7 breast cancer cells (MCF-7/ADR cells) than by the cells treated with the free drugs, single-drug–loaded nanoparticles, or non-biotin–decorated nanoparticles. BNDQ exhibited clear inhibition of both the activity and expression of P-glycoprotein in MCF-7/ADR cells. More importantly, it caused a significant reduction in doxorubicin resistance in MCF-7/ADR breast cancer cells both in vitro and in vivo, among all the groups. Overall, this study suggests that BNDQ has a potential role in the treatment of drug-resistant breast cancer.

High Expression of FAM83B Predicts Poor Prognosis in Patients with Pancreatic Ductal Adenocarcinoma and Correlates with Cell Cycle and Cell Proliferation

FAM83B (family with sequence similarity 83, member B) seems to emerge as a new class of players involved in the development of a variety of malignant tumors. Yet the molecular mechanisms are not well understood. The present study is intended to investigate the expression and function of FAM83B in pancreatic ductal adenocarcinoma (PDAC). In this study, we found that the expression of FAM83B was significantly increased both in PDAC cell lines and PDAC tumor tissues. FAM83B expression was positively related with advanced clinical stage and poor vital status. Higher FAM83B expression predicted shorter overall survival in PDAC patients, regardless of lymphatic metastasis status and histological differentiation. Actually, FAM83B may act as an independent prognostic indicator as well. What's more, down-regulation of FAM83B in PDAC cells contributed to G0/G1 phase arrest and inhibition of cell proliferation. Finally, a subcutaneous xenograft model indicated that knockdown of FAM83B significantly reduced the tumor volume in vivo. Our findings have provided supporting evidence for the potential molecular biomarker role of FAM83B in PDAC. It's of great interest and broad significance to target FAM83B in PDAC, which may conduce to develop a meaningful and effective strategy in the diagnosis and treatment of PDAC.