Co-targeting of EGFR and autophagy signaling is an emerging treatment strategy in metastatic colorectal cancer

Cellular and molecular mechanisms of gastrointestinal cancer liver metastases and drug resistance

Distant metastases and drug resistance account for poor survival of patients with gastrointestinal (GI) malignancies such as gastric cancer, pancreatic cancer, and colorectal cancer. GI cancers most commonly metastasize to the liver, which provides a unique immunosuppressive tumour microenvironment to support the development of a premetastatic niche for tumor cell colonization and metastatic outgrowth. Metastatic tumors often exhibit greater resistance to drugs than primary tumors, posing extra challenges in treatment. The liver metastases and drug resistance of GI cancers are regulated by complex, intertwined, and tumor-dependent cellular and molecular mechanisms that influence tumor cell behavior (e.g. epithelial-to-mesenchymal transition, or EMT), tumor microenvironment (TME) (e.g. the extracellular matrix, cancer-associated fibroblasts, and tumor-infiltrating immune cells), tumor cell-TME interactions (e.g. through cytokines and exosomes), liver microenvironment (e.g. hepatic stellate cells and macrophages), and the route and mechanism of tumor cell dissemination (e.g. circulating tumor cells). This review provides an overview of recent advances in the research on cellular and molecular mechanisms that regulate liver metastases and drug resistance of GI cancers. We also discuss recent advances in the development of mechanism-based therapy for these GI cancers. Targeting these cellular and molecular mechanisms, either alone or in combination, may potentially provide novel approaches to treat metastatic GI malignancies.

Cell Death, by Any Other Name…

Studies trying to understand cell death, this ultimate biological process, can be traced back to a century ago. Yet, unlike many other fashionable research interests, research on cell death is more alive than ever. New modes of cell death are discovered in specific contexts, as are new molecular pathways. But what is "cell death", really? This question has not found a definitive answer yet. Nevertheless, part of the answer is irreversibility, whereby cells can no longer recover from stress or injury. Here, we identify the most distinctive features of different modes of cell death, focusing on the executive final stages. In addition to the final stages, these modes can differ in their triggering stimulus, thus referring to the initial stages. Within this framework, we use a few illustrative examples to examine how intercellular communication factors in the demise of cells. First, we discuss the interplay between cell-cell communication and cell death during a few steps in the early development of multicellular organisms. Next, we will discuss this interplay in a fully developed and functional tissue, the gut, which is among the most rapidly renewing tissues in the body and, therefore, makes extensive use of cell death. Furthermore, we will discuss how the balance between cell death and communication is modified during a pathological condition, i.e., colon tumorigenesis, and how it could shed light on resistance to cancer therapy. Finally, we briefly review data on the role of cell-cell communication modes in the propagation of cell death signals and how this has been considered as a potential therapeutic approach. Far from vainly trying to provide a comprehensive review, we launch an invitation to ponder over the significance of cell death diversity and how it provides multiple opportunities for the contribution of various modes of intercellular communication.

Harnessing Ferroptosis to Overcome Drug Resistance in Colorectal Cancer: Promising Therapeutic Approaches

Drug resistance remains a significant challenge in the treatment of colorectal cancer (CRC). In recent years, the emerging field of ferroptosis, a unique form of regulated cell death characterized by iron-dependent lipid peroxidation, has offered new insights and potential therapeutic strategies for overcoming drug resistance in CRC. This review examines the role of ferroptosis in CRC and its impact on drug resistance. It highlights the distinctive features and advantages of ferroptosis compared to other cell death pathways, such as apoptosis and necrosis. Furthermore, the review discusses current research advances in the field, including novel treatment approaches that target ferroptosis. These approaches involve the use of ferroptosis inducers, interventions in iron metabolism and lipid peroxidation, and combination therapies to enhance the efficacy of ferroptosis. The review also explores the potential of immunotherapy in modulating ferroptosis as a therapeutic strategy. Additionally, it evaluates the strengths and limitations of targeting ferroptosis, such as its selectivity, low side effects, and potential to overcome resistance, as well as challenges related to treatment specificity and drug development. Looking to the future, this review discusses the prospects of ferroptosis-based therapies in CRC, emphasizing the importance of further research to elucidate the interaction between ferroptosis and drug resistance. It proposes future directions for more effective treatment strategies, including the development of new therapeutic approaches, combination therapies, and integration with emerging fields such as precision medicine. In conclusion, harnessing ferroptosis represents a promising avenue for overcoming drug resistance in CRC. Continued research efforts in this field are crucial for optimizing therapeutic outcomes and providing hope for CRC patients.

Overcoming the Challenges of Phytochemicals in Triple Negative Breast Cancer Therapy: The Path Forward

Triple negative breast cancer (TNBC) is a very aggressive subtype of breast cancer that lacks estrogen, progesterone, and HER2 receptor expression. TNBC is thought to be produced by Wnt, Notch, TGF-beta, and VEGF pathway activation, which leads to cell invasion and metastasis. To address this, the use of phytochemicals as a therapeutic option for TNBC has been researched. Plants contain natural compounds known as phytochemicals. Curcumin, resveratrol, and EGCG are phytochemicals that have been found to inhibit the pathways that cause TNBC, but their limited bioavailability and lack of clinical evidence for their use as single therapies pose challenges to the use of these phytochemical therapies. More research is required to better understand the role of phytochemicals in TNBC therapy, or to advance the development of more effective delivery mechanisms for these phytochemicals to the site where they are required. This review will discuss the promise shown by phytochemicals as a treatment option for TNBC.

The potential effect of Schisandrin-B combination with panitumumab in wild-type and mutant colorectal cancer cell lines: Role of apoptosis and autophagy

Panitumumab is an approved monoclonal antibody for the treatment of colorectal cancer (CRC); however, mutations in EGFR signaling pathway resulted in poor response. Schisandrin-B (Sch-B) is a phytochemical that was suggested to protect against inflammation, oxidative stress, and cell proliferation. The present study aimed to investigate the potential effect of Sch-B on panitumumab-induced cytotoxicity in wild-type Caco-2, and mutant HCT-116 and HT-29 CRC cell lines, and the possible underlying mechanisms. CRC cell lines were treated with panitumumab, Sch-B, and their combination. The cytotoxic effect of drugs was determined by MTT assay. The apoptotic potential was assessed in-vitro by DNA fragmentation and caspase-3 activity. Additionally, autophagy was investigated via microscopic detection of autophagosomes and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) measurement of Beclin-1, Rubicon, LC3-II, and Bcl-2 expression. The drug pair enhanced panitumumab cytotoxicity in all CRC cell lines where IC50 of panitumumab was decreased in Caco-2 cell line. Apoptosis was induced through caspase-3 activation, DNA fragmentation, and Bcl-2 downregulation. Caco-2 cell line treated with panitumumab showed stained acidic vesicular organelles, contrariwise, all cell lines treated with Sch-B or the drug pair displayed green fluorescence indicating the lack of autophagosomes. qRT-PCR revealed the downregulation of LC3-II in all CRC cell lines, Rubicon in mutant cell lines, and Beclin-1 in HT-29 cell line only. Sch-B at 6.5 µM promoted panitumumab-induced apoptotic cell death, in-vitro, via caspase-3 activation and Bcl-2 downregulation, rather than autophagic cell death. This novel combination therapy against CRC, allows the reduction of panitumumab dose to guard against its adverse effects.

Autophagy and the Insulin-like Growth Factor (IGF) System in Colonic Cells: Implications for Colorectal Neoplasia

Colorectal cancer (CRC) is one of the most common human malignancies worldwide. Along with apoptosis and inflammation, autophagy is one of three important mechanisms in CRC. The presence of autophagy/mitophagy in most normal mature intestinal epithelial cells has been confirmed, where it has mainly protective functions against reactive oxygen species (ROS)-induced DNA and protein damage. Autophagy regulates cell proliferation, metabolism, differentiation, secretion of mucins and/or anti-microbial peptides. Abnormal autophagy in intestinal epithelial cells leads to dysbiosis, a decline in local immunity and a decrease in cell secretory function. The insulin-like growth factor (IGF) signaling pathway plays an important role in colorectal carcinogenesis. This is evidenced by the biological activities of IGFs (IGF-1 and IGF-2), IGF-1 receptor type 1 (IGF-1R) and IGF-binding proteins (IGF BPs), which have been reported to regulate cell survival, proliferation, differentiation and apoptosis. Defects in autophagy are found in patients with metabolic syndrome (MetS), inflammatory bowel diseases (IBD) and CRC. In neoplastic cells, the IGF system modulates the autophagy process bidirectionally. In the current era of improving CRC therapies, it seems important to investigate the exact mechanisms not only of apoptosis, but also of autophagy in different populations of tumor microenvironment (TME) cells. The role of the IGF system in autophagy in normal as well as transformed colorectal cells still seems poorly understood. Hence, the aim of the review was to summarize the latest knowledge on the role of the IGF system in the molecular mechanisms of autophagy in the normal colon mucosa and in CRC, taking into account the cellular heterogeneity of the colonic and rectal epithelium.

Huaier suppresses pancreatic cancer progression via activating cell autophagy induced ferroptosis

Purpose

The anti-tumour effect of Huaier has been demonstrated in a variety of tumours. Ferroptosis is a newly identified type of programmed cell death accompanied by the accumulation of reactive oxygen species (ROS) and iron in cells and plays a key role in the therapeutic process against malignant tumours. We aimed to explore the potential therapeutic role of Huaier in pancreatic cancer and uncover the relationship between Huaier and ferroptosis.

Methods

CCK8 and colony formation assays were used to determine the proliferation of pancreatic cancer cells (PCs). The levels of cellular ROS were analysed by a fluorescence probe, and the accumulation of cellular iron was showed by Prussian blue staining. The autophagosomes and mitochondrial morphology were characterised by transmission electron microscopy (TEM). The levels of intracellular glutathione (GSH) and lipid peroxidation were measured by the corresponding kits.

Results

The growth inhibitory effect of Huaier on PCs was concentration- and time-dependent, but this effect was significantly attenuated by ferroptosis inhibitors. In addition, Huaier effectively inhibited the GSH–GPX4 antioxidation system and resulted in the massive accumulation of ROS in PCs As shown by TEM, Huaier-treated PCs exhibited a decrease in mitochondrial cristae and a smaller mitochondrion, accompanied by an increase in autophagosomes. Indeed, we found that autophagy can induce ferroptosis in PCs and that Huaier-induced ferroptosis can be suppressed by the autophagosome inhibitor, Wortmannin.

Conclusion

Huaier can activate ferroptosis by inducing autophagy in PCs.

Implication of gut microbiome in immunotherapy for colorectal cancer

Colorectal cancer (CRC) constitutes the third most frequently reported malignancy in the male population and the second most common in women in the last two decades. Colon carcinogenesis is a complex, multifactorial event, resulting from genetic and epigenetic aberrations, the impact of environmental factors, as well as the disturbance of the gut microbial ecosystem. The relationship between the intestinal microbiome and carcinogenesis was relatively undervalued in the last decade. However, its remarkable effect on metabolic and immune functions on the host has been in the spotlight as of recent years. There is a strong relationship between gut microbiome dysbiosis, bowel pathogenicity and responsiveness to anti-cancer treatment; including immunotherapy. Modifications of bacteriome consistency are closely associated with the immunologic response to immunotherapeutic agents. This condition that implies the necessity of gut microbiome manipulation. Thus, creatingan optimal response for CRC patients to immunotherapeutic agents. In this paper, we will review the current literature observing how gut microbiota influence the response of immunotherapy on CRC patients.

Phosphorylated STYK1 restrains the inhibitory role of EGFR in autophagy initiation and EGFR-TKIs sensitivity

Epidermal growth factor receptor (EGFR) plays critical roles in cell proliferation and tumorigenesis. Autophagy has emerged as a potential mechanism involved in the acquired resistance to anti-EGFR treatments, however, the molecular mechanisms has not been fully addressed. In this study, we identified EGFR interacts with STYK1, a positive autophagy regulator, in EGFR kinase activity dependent manner. We found that EGFR phosphorylates STYK1 at Y356 site and STYK1 inhibits activated EGFR mediated Beclin1 tyrosine phosphorylation and interaction between Bcl2 and Beclin1, thus enhances PtdIns3K-C1 complex assembly and autophagy initiation. We also demonstrated that STYK1 depletion increased the sensitivity of NSCLC cells to EGFR-TKIs in vitro and in vivo. Moreover, EGFR-TKIs induced activation of AMPK phosphorylates STYK1 at S304 site. STYK1 S304 collaborated with Y356 phosphorylation to enhance the EGFR-STYK1 interaction and reverse the inhibitory effects of EGFR to autophagy flux. Collectively, these data revealed new roles and cross-talk between STYK1 and EGFR in autophagy regulation and EGFR-TKIs sensitivity in NSCLC.

Crucial Role of Oncogenic KRAS Mutations in Apoptosis and Autophagy Regulation: Therapeutic Implications

KRAS, one of the RAS protein family members, plays an important role in autophagy and apoptosis, through the regulation of several downstream effectors. In cancer cells, KRAS mutations confer the constitutive activation of this oncogene, stimulating cell proliferation, inducing autophagy, suppressing apoptosis, altering cell metabolism, changing cell motility and invasion and modulating the tumor microenvironment. In order to inhibit apoptosis, these oncogenic mutations were reported to upregulate anti-apoptotic proteins, including Bcl-xL and survivin, and to downregulate proteins related to apoptosis induction, including thymine-DNA glycosylase (TDG) and tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL). In addition, KRAS mutations are known to induce autophagy in order to promote cell survival and tumor progression through MAPK and PI3K regulation. Thus, these mutations confer resistance to anti-cancer drug treatment and, consequently, result in poor prognosis. Several therapies have been developed in order to overcome KRAS-induced cell death resistance and the downstream signaling pathways blockade, especially by combining MAPK and PI3K inhibitors, which demonstrated promising results. Understanding the involvement of KRAS mutations in apoptosis and autophagy regulation, might bring new avenues to the discovery of therapeutic approaches for CRCs harboring KRAS mutations.

Immunotherapy as a Therapeutic Strategy for Gastrointestinal Cancer-Current Treatment Options and Future Perspectives

Gastrointestinal (GI) cancer constitutes a highly lethal entity among malignancies in the last decades and is still a major challenge for cancer therapeutic options. Despite the current combinational treatment strategies, including chemotherapy, surgery, radiotherapy, and targeted therapies, the survival rates remain notably low for patients with advanced disease. A better knowledge of the molecular mechanisms that influence tumor progression and the development of optimal therapeutic strategies for GI malignancies are urgently needed. Currently, the development and the assessment of the efficacy of immunotherapeutic agents in GI cancer are in the spotlight of several clinical trials. Thus, several new modalities and combinational treatments with other anti-neoplastic agents have been identified and evaluated for their efficiency in cancer management, including immune checkpoint inhibitors, adoptive cell transfer, chimeric antigen receptor (CAR)-T cell therapy, cancer vaccines, and/or combinations thereof. Understanding the interrelation among the tumor microenvironment, cancer progression, and immune resistance is pivotal for the optimal therapeutic management of all gastrointestinal solid tumors. This review will shed light on the recent advances and future directions of immunotherapy for malignant tumors of the GI system.

Violacein negatively modulates the colorectal cancer survival and epithelial-mesenchymal transition

Violacein is a secondary metabolite produced by several microorganisms including Chromobacterium violaceum, and it is already used in food and cosmetics. However, due to its potent anticancer and low side effects, its molecular action needs to be deeply scrutinized. Therefore, the main objective of this study was to evaluate the violacein's ability to interfere with three cancer hallmarks: growth factors receptor-dependent signaling, proliferation, and epithelial-mesenchymal transition (EMT). Violacein has been associated with the induction of apoptosis in colorectal cancer (CRC) cells. Here, we demonstrate that this molecule is also active in CRC spheroids and inhibits cell migration. Violacein treatment reduced the amount of EGFR and AXL receptors in the HT29 cell line. Accordingly, the inhibition of the AKT, ERK, and PKCδ kinases, which are downstream mediators of the signaling pathways triggered by EGFR and AXL, is detected. Another interesting finding was that even when the cells were stimulated with transforming growth factor-β, the EMT marker (N-cadherin) decreased. Therefore, this study provides further evidence that reinforces the potential of violacein as an antitumor agent, once this biomolecule can "switch off" properties associated with cancer plasticity.

Endocytosis at the Crossroad of Polarity and Signaling Regulation: Learning from Drosophila melanogaster and Beyond

Cellular trafficking through the endosomal–lysosomal system is essential for the transport of cargo proteins, receptors and lipids from the plasma membrane inside the cells and across membranous organelles. By acting as sorting stations, vesicle compartments direct the fate of their content for degradation, recycling to the membrane or transport to the trans-Golgi network. To effectively communicate with their neighbors, cells need to regulate their compartmentation and guide their signaling machineries to cortical membranes underlying these contact sites. Endosomal trafficking is indispensable for the polarized distribution of fate determinants, adaptors and junctional proteins. Conversely, endocytic machineries cooperate with polarity and scaffolding components to internalize receptors and target them to discrete membrane domains. Depending on the cell and tissue context, receptor endocytosis can terminate signaling responses but can also activate them within endosomes that act as signaling platforms. Therefore, cell homeostasis and responses to environmental cues rely on the dynamic cooperation of endosomal–lysosomal machineries with polarity and signaling cues. This review aims to address advances and emerging concepts on the cooperative regulation of endocytosis, polarity and signaling, primarily in Drosophila melanogaster and discuss some of the open questions across the different cell and tissue types that have not yet been fully explored.

How autophagy controls the intestinal epithelial barrier

Macroautophagy/autophagy is a cellular catabolic process that results in lysosome-mediated recycling of organelles and protein aggregates, as well as the destruction of intracellular pathogens. Its role in the maintenance of the intestinal epithelium is of particular interest, as several autophagy-related genes have been associated with intestinal disease. Autophagy and its regulatory mechanisms are involved in both homeostasis and repair of the intestine, supporting intestinal barrier function in response to cellular stress through tight junction regulation and protection from cell death. Furthermore, a clear role has emerged for autophagy not only in secretory cells but also in intestinal stem cells, where it affects their metabolism, as well as their proliferative and regenerative capacity. Here, we review the physiological role of autophagy in the context of intestinal epithelial maintenance and how genetic mutations affecting autophagy contribute to the development of intestinal disease.Abbreviations: AKT1S1: AKT1 substrate 1; AMBRA1: autophagy and beclin 1 regulator 1; AMPK: AMP-activated protein kinase; APC: APC regulator of WNT signaling pathway; ATF6: activating transcription factor 6; ATG: autophagy related; atg16l1[ΔIEC] mice: mice with a specific deletion of Atg16l1 in intestinal epithelial cells; ATP: adenosine triphosphate; BECN1: beclin 1; bsk/Jnk: basket; CADPR: cyclic ADP ribose; CALCOCO2: calcium binding and coiled-coil domain 2; CASP3: caspase 3; CD: Crohn disease; CDH1/E-cadherin: cadherin 1; CF: cystic fibrosis; CFTR: CF transmembrane conductance regulator; CGAS: cyclic GMP-AMP synthase; CLDN2: claudin 2; CoPEC: colibactin-producing E. coli; CRC: colorectal cancer; CYP1A1: cytochrome P450 family 1 subfamily A member 1; DC: dendritic cell; DDIT3: DNA damage inducible transcript 3; DEPTOR: DEP domain containing MTOR interacting protein; DSS: dextran sulfate sodium; EGF: epidermal growth factor; EGFR: epidermal growth factor receptor; EIF2A: eukaryotic translation initiation factor 2A; EIF2AK3: eukaryotic translation initiation factor 2 alpha kinase 3; EIF2AK4/GCN2: eukaryotic translation initiation factor 2 alpha kinase 4; ER: endoplasmic reticulum; ERN1: endoplasmic reticulum to nucleus signaling 1; GABARAP: GABA type A receptor-associated protein; HMGB1: high mobility group box 1; HSPA5/GRP78: heat shock protein family A (Hsp70) member 5; IBD: inflammatory bowel disease; IEC: intestinal epithelial cell; IFN: interferon; IFNG/IFNγ:interferon gamma; IL: interleukin; IRGM: immunity related GTPase M; ISC: intestinal stem cell; LGR5: leucine rich repeat containing G protein-coupled receptor 5; LRRK2: leucine rich repeat kinase 2; MAP1LC3A/LC3: microtubule associated protein 1 light chain 3 alpha; MAPK/JNK: mitogen-activated protein kinase; MAPK14/p38 MAPK: mitogen-activated protein kinase 14; MAPKAP1: MAPK associated protein 1; MAVS: mitochondrial antiviral signaling protein; miRNA: microRNA; MLKL: mixed lineage kinase domain like pseudokinase; MLST8: MTOR associated protein, LST8 homolog; MNV: murine norovirus; MTOR: mechanistic target of rapamycin kinase; NBR1: NBR1 autophagy cargo receptor; NLRP: NLR family pyrin domain containing; NOD: nucleotide binding oligomerization domain containing; NRBF2: nuclear receptor binding factor 2; OPTN: optineurin; OXPHOS: oxidative phosphorylation; P: phosphorylation; Patj: PATJ crumbs cell polarity complex component; PE: phosphatidyl-ethanolamine; PI3K: phosphoinositide 3-kinase; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PIK3R4: phosphoinositide-3-kinase regulatory subunit 4; PPARG: peroxisome proliferator activated receptor gamma; PRR5: proline rich 5; PRR5L: proline rich 5 like; PtdIns3K: phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol 3-phosphate; RB1CC1/FIP200: RB1 inducible coiled-coil 1; RER: rough endoplasmic reticulum; RHEB: Ras homolog, MTORC1 binding; RICTOR: RPTOR independent companion of MTOR complex 2; RIPK1: receptor interacting serine/threonine kinase 1; ROS: reactive oxygen species; RPTOR: regulatory associated protein of MTOR complex 1; RPS6KB1: ribosomal protein S6 kinase B1; SH3GLB1: SH3 domain containing GRB2 like, endophilin B1; SNP: single-nucleotide polymorphism; SQSTM1: sequestosome 1; STAT3: signal transducer and activator of transcription 3; STING1: stimulator of interferon response cGAMP interactor 1; TA: transit-amplifying; TFEB: transcription factor EB; TFE3: transcription factor binding to IGHM enhancer 3; TGM2: transglutaminase 2; TJ: tight junction; TJP1/ZO1: tight junction protein 1; TNBS: 2,4,6-trinitrobenzene sulfonic acid; TNF/TNFα: tumor necrosis factor; Tor: target of rapamycin; TRAF: TNF receptor associated factor; TRIM11: tripartite motif containing 11; TRP53: transformation related protein 53; TSC: TSC complex subunit; Ub: ubiquitin; UC: ulcerative colitis; ULK1: unc-51 like autophagy activating kinase 1; USO1/p115: USO1 vesicle transport factor; UVRAG: UV radiation resistance associated; WIPI: WD repeat domain, phosphoinositide interacting; WNT: WNT family member; XBP1: X-box binding protein 1; ZFYVE1/DFCP1: zinc finger FYVE-type containing 1.

The Implication of Autophagy in Gastric Cancer Progression

Gastric cancer is the fifth most common malignancy and the third leading cause of cancer-related death worldwide. The three entirely variable entities have distinct epidemiology, molecular characteristics, prognosis, and strategies for clinical management. However, many gastric tumors appear to be resistant to current chemotherapeutic agents. Moreover, a significant number of gastric cancer patients, with a lack of optimal treatment strategies, have reduced survival. In recent years, multiple research data have highlighted the importance of autophagy, an essential catabolic process of cytoplasmic component digestion, in cancer. The role of autophagy as a tumor suppressor or tumor promoter mechanism remains controversial. The multistep nature of the autophagy process offers a wide array of targetable points for designing novel chemotherapeutic strategies. The purpose of this review is to summarize the current knowledge regarding the interplay between gastric cancer development and the autophagy process and decipher the role of autophagy in this kind of cancer. A plethora of different agents that direct or indirect target autophagy may be a novel therapeutic approach for gastric cancer patients.

Resistance to anti-EGFR therapies in metastatic colorectal cancer: underlying mechanisms and reversal strategies

Cetuximab and panitumumab are monoclonal antibodies (mAbs) against epidermal growth factor receptor (EGFR) that are effective agents for metastatic colorectal cancer (mCRC). Cetuximab can prolong survival by 8.2 months in RAS wild-type (WT) mCRC patients. Unfortunately, resistance to targeted therapy impairs clinical use and efficiency. The mechanisms of resistance refer to intrinsic and extrinsic alterations of tumours. Multiple therapeutic strategies have been investigated extensively to overcome resistance to anti-EGFR mAbs. The intrinsic mechanisms include EGFR ligand overexpression, EGFR alteration, RAS/RAF/PI3K gene mutations, ERBB2/MET/IGF-1R activation, metabolic remodelling, microsatellite instability and autophagy. For intrinsic mechanisms, therapies mainly cover the following: new EGFR-targeted inhibitors, a combination of multitargeted inhibitors, and metabolic regulators. In addition, new cytotoxic drugs and small molecule compounds increase the efficiency of cetuximab. Extrinsic alterations mainly disrupt the tumour microenvironment, specifically immune cells, cancer-associated fibroblasts (CAFs) and angiogenesis. The directions include the modification or activation of immune cells and suppression of CAFs and anti-VEGFR agents. In this review, we focus on the mechanisms of resistance to anti-EGFR monoclonal antibodies (anti-EGFR mAbs) and discuss diverse approaches to reverse resistance to this therapy in hopes of identifying more mCRC treatment possibilities.

Role of autophagy in cholangiocarcinoma: An autophagy-based treatment strategy

Cholangiocarcinomas (CCAs) are diverse biliary epithelial tumours involving the intrahepatic, perihilar and distal parts of the biliary tree. The three entirely variable entities have distinct epidemiology, molecular characteristics, prognosis and strategy for clinical management. However, many cholangiocarcinoma tumor-cells appear to be resistant to current chemotherapeutic agents. The role of autophagy and the therapeutic value of autophagy-based therapy are largely unknown in CCA. The multistep nature of autophagy offers a plethora of regulation points, which are prone to be deregulated and cause different human diseases, including cancer. However, it offers multiple targetable points for designing novel therapeutic strategies. Tumor cells have evolved to use autophagy as an adaptive mechanism for survival under stressful conditions such as energy imbalance and hypoxic region of tumors within the tumor microenvironment, but also to increase invasiveness and resistance to chemotherapy. The purpose of this review is to summarize the current knowledge regarding the interplay between autophagy and cholangiocarcinogenesis, together with some preclinical studies with agents that modulate autophagy in order to induce tumor cell death. Altogether, a combinatorial strategy, which comprises the current anti-cancer agents and autophagy modulators, would represent a positive CCA patient approach.

A dual-targeted molecular therapy of PP242 and cetuximab plays an anti-tumor effect through EGFR downstream signaling pathways in colorectal cancer

Background

Epidermal growth factor receptor (EGFR) and its downstream Ras-mitogen-activated protein kinase kinase (MAPKK, MEK)-extracellular regulated protein kinase (ERK) signaling pathway and phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt)-mammalian target of rapamycin (mTOR) signaling pathway play important roles in the pathogenesis of colorectal cancer (CRC). The combination therapy of anti-EGFR and anti-mTOR needs to be explored.

Methods

Here we combined the anti-EGFR monoclonal antibody cetuximab (CTX) with the mTOR inhibitor PP242 in CRC cell lines and mouse xenograft models and discussed the changes of EGFR downstream signaling pathways of CRC cell lines.

Results

In HT-29 cells and Caco-2 cells, combined application of CTX and PP242 significantly inhibited the proliferation of CRC cells in vivo and in vitro. In BRAF wild-type Caco-2 cells, combined application of CTX and PP242 inhibited the activation of the EGFR and its downstream signaling pathways.

Conclusions

Our research further demonstrates the effectiveness of the combined application of CTX and PP242 in inhibiting CRC cell lines from the perspective of cell proliferation, cell cycle, apoptosis, and mouse xenografts. We revealed that the combined application of CTX and PP242 can inhibit tumor growth and proliferation by inhibiting the phosphorylation of key molecules in EGFR downstream MEK-ERK and MEK 4/7 (MKK)-c-Jun N-terminal kinase (JNK) signaling pathways in BRAF wild-type CRC cells. In addition, we found that in BRAF mutant CRC cells, the monotherapy of PP242 resulted in negative feedback increased EGFR phosphorylation rates, accompanied by significant up-regulation of downstream MEK and ERK phosphorylation.

Knockdown lncRNA CRNDE enhances temozolomide chemosensitivity by regulating autophagy in glioblastoma

Background

The regulatory roles of long non-coding RNA (lncRNA) CRNDE in temozolomide (TMZ) chemoresistance to glioblastoma multiforme (GBM) are still poorly understood. Therefore, the function, characteristics, and possible mechanism of CRNDE in TMZ-induced chemoresistance to GBM were explored.

Methods

Firstly, the expression level of CRNDE in 58 cases of glioma tissue specimens and 30 cases of normal brain tissues were tested by qRT-PCR. Meanwhile, the correlation between CRNDE expression level, the clinicopathological characteristics, and survival time of patients with glioma were analyzed. Then, the CRNDE expression in various glioma cell lines was detected, and CRNDE knockdown cell models were constructed. Subsequently, to explore the effect of CRNDE on chemosensitivity to TMZ, cell viability was detected by the CCK-8 assay and IC₅₀ values, and cell proliferation was detected by cell clone assay and EdU assay, as well as cell survival was detected by apoptosis with flow cytometry under TMZ treatment. Further, the expression of drug-resistance protein ABCG2, autophagy related proteins, and PI3K/Akt/mTOR pathway were measured by western blot or qRT-PCR in TMZ-treated glioma cells. Finally, the mouse tumor xenograft model was established and the tumor volume and weight were measured, and ABCG2 expression was conducted by immunohistochemistry assay.

Results

The integrated results demonstrated lncRNA CRNDE was a poor prognosis factor for GBM patient, which was upregulated in patients who were resistant to TMZ, and closely associated with chemotherapeutic response status to TMZ treatment. Further, functional assays revealed that knockdown of CRNDE could notably reduce glioma cell viability and proliferation, and elevate cell apoptosis to enhance the chemosensitivity to TMZ in vitro and in vivo. Mechanistically, the depression of CRNDE could diminish the expression of LC3 II/I, Beclin1 and Atg5 and increase the p62 expression level to inhibit autophagy due to the activation of PI3K/Akt/mTOR pathway as well as highly correlated with ABCG2 expression.

Conclusions

Overall, the study provided that lncRNA CRNDE is a reliable clinical predictor of outcome and prognosis and a potential biomarker for predicting TMZ treatment response in GBM by modulating the autophagy through PI3K/Akt/mTOR pathway and ABCG2 expression which may be a novel therapeutic target for regulating TMZ sensitivity to GBM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02153-x.

Pseudomonas Exotoxin A-Based Immunotherapy Targeting CCK2R-Expressing Colorectal Malignancies: An In Vitro and In Vivo Evaluation

Cholecystokinin-2 receptor (CCK2R) has been proven to be a specific biomarker for colorectal malignancies. Immunotoxins are a valuable class of immunotherapy agents consisting of a targeting element and a bacterial or plant toxin. Previous work demonstrated that targeting CCK2R is a good therapeutic strategy for the treatment of colorectal cancer (CRC). In the present study, we developed a new version of CCK2R-targeting immunotoxin GD9P using a targeted peptide, GD9, as the binding motif and a truncated Pseudomonas exotoxin A (PE38) as the cytokiller. BALB/c nude mice were treated with different doses of GD9P, and pharmacodynamics, pharmacokinetic, and toxicological data were obtained throughout this study. Compared to the parental immunotoxin rCCK8PE38, GD9P exhibited about 1.5-fold yield, higher fluorescence intensity, and increased antitumor activity against human CRC in vitro and in vivo. The IC50 values of GD9P in vitro ranged from 1.61 to 4.55 nM. Pharmacokinetic studies were conducted in mice with a T1/2 of 69.315 min. When tumor-bearing nude mice were treated with GD9P at doses ≥2 mg/kg for five doses, a rapid shrinkage in tumor volume and, in some cases, complete remission was observed. A preliminary safety evaluation demonstrated a good safety profile of GD9P as a Pseudomonas exotoxin A-based immunotherapy. The therapy in combination with oxaliplatin can increase the antitumor efficacy and reduce the toxic side effects caused by chemotherapy. In conclusion, the data support the use of GD9P as a promising immunotherapy targeting CCK2R-expressing colorectal malignancies.

Combination of two miRNAs has a stronger effect on stimulating apoptosis, inhibiting cell growth, and increasing erlotinib sensitivity relative to single miRNA in A549 lung cancer cells

Despite the dramatic efficacy of EGFR-TKIs, most of non-small cell lung cancer patients ultimately develop resistance to these agents. In this study, we explored the effects of miRNA-125a-5p and miRNA-145, alone or in combination, EGFR expression, cell growth and sensitivity of the NSCLC cells to erlotinib. The expression of EGFR was measured using RT-qPCR and Western blotting. The effect of miRNAs and erlotinib on cell growth and survival was assessed by trypan blue assay and MTT assay, respectively. Apoptosis was measured using ELISA cell death assay. We found that transfection of miRNA-125a-5p and miRNA-145 significantly inhibited the expression of EGFR mRNA and protein in a time-dependent manner (p < 0.05 vs. blank control or negative control miRNA). ANOVA and Bonferroni's test were used to ascertain significant differences between groups. Other experiments indicated that upregulation of each of miRNA-125a-5p or miRNA-145 inhibited cell growth, induced apoptosis, and markedly decreased the IC₅₀ value of erlotinib in A549 lung cancer cells (p < 0.05). Moreover, the combination of two miRNAs showed a stronger effect on cells survival, apoptosis, and drug sensitivity, relative to single miRNA (p < 0.05). The results of our study indicate that the therapeutic delivery of miRNA-145 and miRNA-125a-5p to lung cancer may inhibit cell proliferation, trigger apoptosis, and sensitize lung cancer cells to EGFR-TKIs.

Prognostic Significance of Autophagy-Relevant Gene Markers in Colorectal Cancer

Background

Colorectal cancer (CRC) is a common malignant solid tumor with an extremely low survival rate after relapse. Previous investigations have shown that autophagy possesses a crucial function in tumors. However, there is no consensus on the value of autophagy-associated genes in predicting the prognosis of CRC patients. This work screens autophagy-related markers and signaling pathways that may participate in the development of CRC, and establishes a prognostic model of CRC based on autophagy-associated genes.

Methods

Gene transcripts from the TCGA database and autophagy-associated gene data from the GeneCards database were used to obtain expression levels of autophagy-associated genes, followed by Wilcox tests to screen for autophagy-related differentially expressed genes. Then, 11 key autophagy-associated genes were identified through univariate and multivariate Cox proportional hazard regression analysis and used to establish prognostic models. Additionally, immunohistochemical and CRC cell line data were used to evaluate the results of our three autophagy-associated genes EPHB2, NOL3, and SNAI1 in TCGA. Based on the multivariate Cox analysis, risk scores were calculated and used to classify samples into high-risk and low-risk groups. Kaplan-Meier survival analysis, risk profiling, and independent prognosis analysis were carried out. Receiver operating characteristic analysis was performed to estimate the specificity and sensitivity of the prognostic model. Finally, GSEA, GO, and KEGG analysis were performed to identify the relevant signaling pathways.

Results

A total of 301 autophagy-related genes were differentially expressed in CRC. The areas under the 1-year, 3-year, and 5-year receiver operating characteristic curves of the autophagy-based prognostic model for CRC were 0.764, 0.751, and 0.729, respectively. GSEA analysis of the model showed significant enrichment in several tumor-relevant pathways and cellular protective biological processes. The expression of EPHB2, IL-13, MAP2, RPN2, and TRAF5 was correlated with microsatellite instability (MSI), while the expression of IL-13, RPN2, and TRAF5 was related to tumor mutation burden (TMB). GO analysis showed that the 11 target autophagy genes were chiefly enriched in mRNA processing, RNA splicing, and regulation of the mRNA metabolic process. KEGG analysis showed enrichment mainly in spliceosomes. We constructed a prognostic risk assessment model based on 11 autophagy-related genes in CRC.

Conclusion

A prognostic risk assessment model based on 11 autophagy-associated genes was constructed in CRC. The new model suggests directions and ideas for evaluating prognosis and provides guidance to choose better treatment strategies for CRC.

Rotundic Acid Regulates the Effects of Let-7f-5p on Caco2 Cell Proliferation

BACKGROUND & OBJECTIVE

Nowadays, the interaction between natural products and microRNAs provides a promising field for exploring the chemopreventive agents for various cancers. As a member of microRNAs, the expression of let-7f-5p is universally downregulated in Colorectal Cancer (CRC). The present study aimed to uncover the function of let-7f-5p in the proliferation of human colon cancer cell line Caco2 and explored chemopreventive agents from natural resources that can prevent the development of CRC.

METHODS

Herein, Caco2 cells were transfected with let-7f-5p mimic and inhibitor to manipulate let-7f-5p levels, and the expression of let-7f-5p was performed by RT-qPCR. Next, we determined how let-7f-5p regulates Caco2 cell proliferation by using MTT, wound-healing, cell cycle, and colony formation assays. Besides, to further understand the effect of let-7f-5p, we evaluated the protein level of AMER3 and SLC9A9 by using western blotting assays.

RESULTS

The results showed a suppressive function of let-7f-5p on Caco2 cell proliferation and then put forward a triterpenoid (Rotundic Acid, RA) which significant antagonized the effect of cell proliferation, restitution after wounding, and colony formation caused by let-7f-5p. Moreover, the western blot results further indicated that the inhibitory effect of RA might be due to its suppressive role in let-7f-5p-targeted AMER3 and SLC9A9 regulation.

CONCLUSION

Our validation study results confirmed that let-7f-5p was a potent tumor suppressor gene of Caco2 cell proliferation, and RA showed as a regulator of the effect of let-7f-5p on cell proliferation and then could be a potential chemopreventive agent for CRC treatment.

LncRNA DNAJC3-AS1 Regulates Fatty Acid Synthase via the EGFR Pathway to Promote the Progression of Colorectal Cancer

Colorectal cancer (CRC) is one of the most common cancers worldwide. Recent studies have shown that long non-coding RNAs (lncRNAs) are involved in tumorigenesis and the development of CRC. By constructing a differential lncRNA expression profile, we screened gene chips and found that DNAJC3-AS1 was highly expressed in CRC tissues and was associated with poor prognosis in patients with CRC. Further, we proved through assays such as wound healing, colony formation, and Cell Counting Kit-8 (CCK8) that interfering with DNAJC3-AS1 could reduce the proliferation, migration, and invasion of CRC cells. Mechanically, we found that DNAJC3-AS1 regulates fatty acid synthase to promote the progression of CRC via the epidermal growth factor receptor/phosphatidylinositol 3-kinase/protein kinase B/nuclear factor κB signaling pathway. Therefore, DNAJC3-AS1 may be a new target for the diagnosis and therapy of CRC.

ATG7-dependent and independent autophagy determine the type of treatment in lung cancer

Based on the role of ATG7 in the initiation of autophagy, autophagy can be divided into ATG7-dependent selective autophagy and ATG7-independent alternative autophagy. However, the detailed roles of two different types of autophagy in antitumor therapy have not been fully elucidated so far. Here, we for the first time demonstrated an investigational inducer, w09, could induce both selective autophagy and alternative autophagy in NSCLC, but the phenotypes of these two kinds of autophagy are different：(1) w09-induced selective autophagy mainly promoted cell apoptosis, while w09-triggered alternative autophagy markedly induced autophagic cell death in NSCLC；(2) w09-induced ATG7 dependent autophagy mainly promoted the accumulation of SQSTM1/p62, while w09-triggered ATG7 independent autophagy markedly accelerated the degradation of SQSTM1/p62. These above results were further confirmed by knockout ATG7 gene in A549 cells or restoration of ATG7 function in H1650 cells. Deletion of ATG7 gene markedly attenuated the effect of w09-induced autophagy or apoptosis on A549 cells, while restoration of functional ATG7 markedly enhanced the effect of w09-induced autophagy and apoptosis on H1650 cells. Mechanistically, we further revealed that w09 induced two different types of autophagy through inhibiting PI3K/AKT/mTOR signaling pathway. Notably, compared with A549WT xenograft model, the in vivo antitumor effect of w09 or Taxel on the ATG7-deficient A549 xenograft model was significantly attenuated. Therefore, a special attention must be paid to distinguish which kinds of autophagy have been induced by autophagy inducers with antitumor agents by targeting PI3K/AKT/mTOR signaling pathway.

Autophagy and salivary gland cancer: A putative target for salivary gland tumors

Salivary gland carcinomas are a group of heterogeneous tumors of different histological subtypes, presenting relatively low incidence but the entire variable of types. Although novel treatment options for salivary gland carcinomas patients' outcomes have improved, the treatment of this type of cancer is still not standardized. In addition, a significant number of patients, with a lack of optimal treatment strategies, have reduced survival. In the last two decades, a plethora of evidence pointed to the importance of autophagy, an essential catabolic process of cytoplasmatic component digestion, in cancer. In vitro and in vivo studies highlight the importance of autophagy in salivary gland carcinomas development as a tumor suppressor or promoter mechanism. Despite the potential of autophagy in salivary gland carcinomas development, no therapies are currently available that specifically focus on autophagy modulation in salivary gland carcinomas. In this review, we summarize current knowledge and clinical trials in regard to the interplay between autophagy and the development of salivary gland carcinomas. Autophagy manipulation may be a putative therapeutic strategy for salivary gland carcinomas patients.

Kinome scale profiling of venom effects on cancer cells reveals potential new venom activities

The search for novel and relevant cancer therapeutics is continuous and ongoing. Cancer adaptations, resulting in therapeutic treatment failures, fuel this continuous necessity for new drugs to novel targets. Recently, researchers have started to investigate the effect of venoms and venom components on different types of cancer, investigating their mechanisms of action. Receptor tyrosine kinases (RTKs) comprise a family of highly conserved and functionally important druggable targets for cancer therapy. This research exploits the novelty of complex venom mixtures to affect phosphorylation of the epidermal growth factor receptor (EGFR) and related RTK family members, dually identifying new activities and unexplored avenues for future cancer and venom research. Six whole venoms from diverse species taxa, were evaluated for their ability to illicit changes in the phosphorylated expression of a panel of 49 commonly expressed RTKs. The triple negative breast cancer cell line MDA-MB-468 was treated with optimised venom doses, pre-determined by SDS PAGE and Western blot analysis. The phosphorylated expression levels of 49 RTKs in response to the venoms were assessed with the use of Human Phospho-RTK Arrays and analysed using ImageLab 5.2.1 analysis software (BioRad). Inhibition of EGFR phosphorylation occurred with treatment of venom from Acanthoscurria geniculata (Theraphosidae), Heterometrus swammerdami (Scorpionidae), Crotalus durissus vegrandis (Crotalidae) and Naja naja (Elapidae). Western green mamba Dendroaspis viridis venom increased EGFR phosphorylation. Eph, HGFR and HER were the most affected receptor families by venoms. Whilst the importance of these changes in terms of effect on MDA-MB-468 cells' long-term viability and functionality are still unclear, the findings present exciting opportunities for further investigation as potential drug targets in cancer and as tools to understand better how these pathways interact.

Decyl caffeic acid inhibits the proliferation of colorectal cancer cells in an autophagy-dependent manner in vitro and in vivo

The treatment of human colorectal cancer (CRC) cells through suppressing the abnormal survival signaling pathways has recently become a significant area of focus. In this study, our results demonstrated that decyl caffeic acid (DC), one of the novel caffeic acid derivatives, remarkedly suppressed the growth of CRC cells both in vitro and in vivo. The inhibitory effects of DC on CRC cells were investigated in an in vitro cell model and in vivo using a xenograft mouse model. CRC cells were treated with DC at various dosages (0, 10, 20 and 40 μM), and cell survival, the apoptotic index and the autophagy level were measured using an MTT assay and flow cytometry analysis, respectively. The signaling cascades in CRC were examined by Western blot assay. The anti-cancer effects of DC on tumor growth were examined by using CRC HCT-116 cells implanted in an animal model. Our results indicated that DC differentially suppressed the growth of CRC HT-29 and HCT-116 cells through an enhancement of cell-cycle arrest at the S phase. DC inhibited the expression of cell-cycle regulators, which include cyclin E and cyclin A proteins. The molecular mechanisms of action were correlated to the blockade of the STAT3 and Akt signaling cascades. Strikingly, a high dosage of DC prompted a self-protection action through inducing cell-dependent autophagy in HCT-116 cells. Suppression of autophagy induced cell death in the treatment of DC in HCT-116 cells. DC seemed to inhibit cell proliferation of CRC differentially, and the therapeutic advantage appeared to be autophagy dependent. Moreover, consumption of DC blocked the tumor growth of colorectal adenocarcinoma in an experimental animal model. In conclusion, our results suggested that DC could act as a therapeutic agent through the significant suppression of tumor growth of human CRC cells.

The Resistance Mechanisms of Checkpoint Inhibitors in Solid Tumors

The emergence of cancer immunotherapy has already shown some remarkable results, having changed the treatment strategy in clinical practice for solid tumors. Despite these promising long-term responses, patients seem to lack the ability to respond to immune checkpoint inhibitors, thus demonstrating a primary resistance to immunotherapy. Moreover, a significant number of patients who initially respond to treatment eventually acquire resistance to immunotherapy. Both resistance mechanisms are a result of a complex interaction among different molecules, pathways, and cellular processes. Several resistance mechanisms, such as tumor microenvironment modification, autophagy, genetic and epigenetic alterations, tumor mutational burden, neo-antigens, and modulation of gut microbiota have already been identified, while more continue to be uncovered. In this review, we discuss the latest milestones in the field of immunotherapy, resistance mechanisms against this type of therapy as well as putative therapeutic strategies to overcome resistance in solid tumors.

Over-expression of EGFR regulated by RARA contributes to 5-FU resistance in colon cancer

A promising new strategy for cancer therapy is to target the autophagic pathway. However, comprehensive characterization of autophagy genes and their clinical relevance in cancer is still lacking. Here, we systematically characterized alterations of autophagy genes in multiple cancer lines by analyzing data from The Cancer Genome Atlas and CellMiner database. Interactions between autophagy genes and clinically actionable genes (CAGs) were identified by analyzing co-expression, protein-protein interactions (PPIs) and transcription factor (TF) data. A key subnetwork was identified that included 18 autophagy genes and 22 CAGs linked by 28 PPI pairs and 1 TF-target pair, which was EGFR targeted by RARA. Alterations in the expression of autophagy genes were associated with patient survival in multiple cancer types. RARA and EGFR were associated with worse survival in colorectal cancer patients. The regulatory role of EGFR in 5-FU resistance was validated in colon cancer cells in vivo and in vitro. EGFR contributed to 5-FU resistance in colon cancer cells through autophagy induction, and EGFR overexpression in 5-FU resistant colon cancer was regulated by RARA. The present study provides a comprehensive analysis of autophagy in different cancer cell lines and highlights the potential clinical utility of targeting autophagy genes.

EGFR signaling pathway occupies an important position in cancer-related downstream signaling pathways of Pyk2

Proline-rich tyrosine kinase 2 (Pyk2) is a member of focal adhesion kinase (FAK) non-receptor tyrosine kinase family and has been found to promote cancer cell survival, proliferation, migration, invasion, and metastasis. Pyk2 takes part in different carcinogenic signaling pathways to promote cancer progression, including epidermal growth factor receptor (EGFR) signaling pathway. EGFR signaling pathway is a traditional carcinogenic signaling pathway, which plays a critical role in tumorigenesis and tumor progression. FAK inhibitors have been reported to fail to get the ideal anti-cancer outcomes because of activation of EGFR signaling pathway. Better understanding of Pyk2 downstream targets and interconnectivity between Pyk2 and carcinogenic EGFR signaling pathway will help finding more effective targets for clinical anti-cancer combination therapies. Thus, the interconnectivity between Pyk2 and EGFR signaling pathway, which regulates tumor development and metastasis, needs to be elucidated. In this review, we summarized the downstream targets of Pyk2 in cancers, focused on the connection between Pyk2 and EGFR signaling pathway in different cancer types, and provided a new overview of the roles of Pyk2 in EGFR signaling pathway and cancer development.

Overcoming malignant cell-based mechanisms of resistance to immune checkpoint blockade antibodies

Traditional cancer treatment approaches have focused on surgery, radiation therapy, and cytotoxic chemotherapy. However, with rare exceptions, metastatic cancers were considered to be incurable by traditional therapy. Over the past 20 years a fourth modality - immunotherapy - has emerged as a potentially curative approach for patients with advanced metastatic cancer. However, in many patients cancer "finds a way" to evade the anti-tumor effects of immunotherapy. Immunotherapy resistance mechanisms can be employed by both cancer cells and the non-cancer elements of tumor microenvironment. This review focuses on the resistance mechanisms that are specifically mediated by cancer cells. In order to extend the impact of immunotherapy to more patients and across all cancer types, and to inhibit the development of acquired resistance, the underlying biology driving immune escape needs to be better understood. Elucidating mechanisms of immune escape may shed light on new therapeutic targets, and lead to successful combination therapeutic strategies.

Promising Therapeutic Efficacy of GC1118, an Anti-EGFR Antibody, against KRAS Mutation-Driven Colorectal Cancer Patient-Derived Xenografts

Epidermal growth factor receptor (EGFR)-targeted monoclonal antibodies, including cetuximab and panitumumab, are used to treat metastatic colorectal cancer (mCRC). However, this treatment is only effective for a small subset of mCRC patients positive for the wild-type KRAS GTPase. GC1118 is a novel, fully humanized anti-EGFR IgG1 antibody that displays potent inhibitory effects on high-affinity EGFR ligand-induced signaling and enhanced antibody-mediated cytotoxicity. In this study, using 51 CRC patient-derived xenografts (PDXs), we showed that KRAS mutants expressed remarkably elevated autocrine levels of high-affinity EGFR ligands compared with wild-type KRAS. In three KRAS-mutant CRCPDXs, GC1118 was more effective than cetuximab, whereas the two agents demonstrated comparable efficacy against three wild-type KRAS PDXs. Persistent phosphatidylinositol-3-kinase (PI3K)/AKT signaling was thought to underlie resistance to GC1118. In support of these findings, a preliminary improved anti-cancer response was observed in a CRC PDX harboring mutated KRAS with intrinsically high AKT activity using GC1118 combined with the dual PI3K/mammalian target of rapamycin (mTOR)/AKT inhibitor BEZ-235, without observed toxicity. Taken together, the superior antitumor efficacy of GC1118 alone or in combination with PI3K/mTOR/AKT inhibitors shows great therapeutic potential for the treatment of KRAS-mutant mCRC with elevated ratios of high- to low-affinity EGFR ligands and PI3K-AKT pathway activation.

Insight Into the Role of Autophagy in Osteosarcoma and Its Therapeutic Implication

Osteosarcoma is an aggressive bone cancer that frequently metastasizes to the lungs. The cytotoxicity of most chemotherapeutics and targeted drugs in the treatment of osteosarcoma is partially lessened. Furthermore, there is a poor response to current chemo- and radiotherapy for both primary lesions and pulmonary metastases of osteosarcoma. There is a clear need to explore promising drug candidates that could improve the efficacy of osteosarcoma treatment. Autophagy, a dynamic and highly conserved catabolic process, has dual roles in promoting cell survival as well as cell death. The role of autophagy has been investigated extensively in different tumor types, and a growing body of research has highlighted the potential value of using autophagy in clinical therapy. Here, we address significant aspects of autophagy in osteosarcoma, including its functions, modulation, and possible therapeutic applications.

At a glance: A history of autophagy and cancer

Since the first discovery of the lysosome and the definition of autophagy by Christian de Duve more than 60 years ago, research on autophagy, a process targeting cytoplasmic materials for lysosomal degradation and recycling, has expanded dramatically. This research has extended our understanding of the basic mechanism of autophagy as well as its role in pathophysiology. Autophagy deficiency has been reported to be involved in numerous diseases, among which cancer has been extensively studied, in part because autophagy appears to play a dual role, depending on the stage of tumorigenesis. In this review, we will briefly revisit the intriguing history of autophagy and cancer, underscoring the importance of harnessing this pathway for the benefit of human health.

Prucalopride inhibits lung cancer cell proliferation, invasion, and migration through blocking of the PI3K/AKT/mTor signaling pathway

Lung cancer is the main cause of cancer incidence and mortality around the world. Prucalopride is an agonist for the 5-hydroxytryptamine 4 receptor, but it was unknown whether prucalopride could be used to treat lung cancer. To investigate the biological effects of prucalopride on proliferation, apoptosis, invasion, and migration of lung cancer cells, and its underlying molecular mechanism in the progression of lung cancer, we performed this study. The Cell Counting Kit 8 assay was used to measure the proliferation of A549/A427 lung cancer cells treated with prucalopride. Transwell assay was applied to evaluate cell invasion and migration. Cell apoptosis was detected by flow cytometry and Western blot analyses. The expression levels of related proteins in the PI3K/AKT/mTor signaling pathway were analyzed by Western blotting. Prucalopride inhibited the proliferation, invasion, and migration of A549/A427 human lung cancer cells. It also induced autophagy and apoptosis and decreased the expression of the phosphorylated protein kinase B (AKT) and mammalian target of rapamycin (mTor) in these cells. This study implied an inhibitory role for prucalopride in the progression of human lung cancer.

The emergence of drug resistance to targeted cancer therapies: Clinical evidence

For many decades classical anti-tumor therapies included chemotherapy, radiation and surgery; however, in the last two decades, following the identification of the genomic drivers and main hallmarks of cancer, the introduction of therapies that target specific tumor-promoting oncogenic or non-oncogenic pathways, has revolutionized cancer therapeutics. Despite the significant progress in cancer therapy, clinical oncologists are often facing the primary impediment of anticancer drug resistance, as many cancer patients display either intrinsic chemoresistance from the very beginning of the therapy or after initial responses and upon repeated drug treatment cycles, acquired drug resistance develops and thus relapse emerges, resulting in increased mortality. Our attempts to understand the molecular basis underlying these drug resistance phenotypes in pre-clinical models and patient specimens revealed the extreme plasticity and adaptive pathways employed by tumor cells, being under sustained stress and extensive genomic/proteomic instability due to the applied therapeutic regimens. Subsequent efforts have yielded more effective inhibitors and combinatorial approaches (e.g. the use of specific pharmacologic inhibitors with immunotherapy) that exhibit synergistic effects against tumor cells, hence enhancing therapeutic indices. Furthermore, new advanced methodologies that allow for the early detection of genetic/epigenetic alterations that lead to drug chemoresistance and prospective validation of biomarkers which identify patients that will benefit from certain drug classes, have started to improve the clinical outcome. This review discusses emerging principles of drug resistance to cancer therapies targeting a wide array of oncogenic kinases, along with hedgehog pathway and the proteasome and apoptotic inducers, as well as epigenetic and metabolic modulators. We further discuss mechanisms of resistance to monoclonal antibodies, immunomodulators and immune checkpoint inhibitors, potential biomarkers of drug response/drug resistance, along with possible new therapeutic avenues for the clinicians to combat devastating drug resistant malignancies. It is foreseen that these topics will be major areas of focused multidisciplinary translational research in the years to come.

What sustains the multidrug resistance phenotype beyond ABC efflux transporters? Looking beyond the tip of the iceberg

Identification of multidrug (MDR) efflux transporters that belong to the ATP-Binding Cassette (ABC) superfamily, represented an important breakthrough for understanding cancer multidrug resistance (MDR) and its possible overcoming. However, recent data indicate that drug resistant cells have a complex intracellular physiology that involves constant changes in energetic and oxidative-reductive metabolic pathways, as well as in the molecular circuitries connecting mitochondria, endoplasmic reticulum (ER) and lysosomes. The aim of this review is to discuss the key molecular mechanisms of cellular reprogramming that induce and maintain MDR, beyond the presence of MDR efflux transporters. We specifically highlight how cancer cells characterized by high metabolic plasticity - i.e. cells able to shift the energy metabolism between glycolysis and oxidative phosphorylation, to survive both the normoxic and hypoxic conditions, to modify the cytosolic and mitochondrial oxidative-reductive metabolism, are more prone to adapt to exogenous stressors such as anti-cancer drugs and acquire a MDR phenotype. Similarly, we discuss how changes in mitochondria dynamics and mitophagy rates, changes in proteome stability ensuring non-oncogenic proteostatic mechanisms, changes in ubiquitin/proteasome- and autophagy/lysosome-related pathways, promote the cellular survival under stress conditions, along with the acquisition or maintenance of MDR. After dissecting the complex intracellular crosstalk that takes place during the development of MDR, we suggest that mapping the specific adaptation pathways underlying cell survival in response to stress and targeting these pathways with potent pharmacologic agents may be a new approach to enhance therapeutic efficacy against MDR tumors.

Discovery of the Anti-Tumor Mechanism of Calycosin Against Colorectal Cancer by Using System Pharmacology Approach

BACKGROUND The aim of our study was to elucidate the biological targets and pharmacological mechanisms for calycosin (CC) against colorectal cancer (CRC) through an approach of system pharmacology. MATERIAL AND METHODS Using a web-based platform, all CRC-causing genes were identified using a database of gene-disease associations (DisGeNET), and all well-known genes of CC identified using the databases of prediction of protein targets of small molecules (Swiss Target Prediction), drug classification, and target prediction (SuperPred). The carefully selected genes of CRC and CC were concurrently constructed by using a database of functional protein association networks (STRING), and use of software for visualizing complex networks (Cytoscape), characterized with production of protein-protein interaction (PPI) network of CC against CRC. The important biological targets of CC against CRC were identified through topological analysis, then the biological processes and molecular pathways of CC against CRC were further revealed for testing these important biotargets by enrichment assays. RESULTS We found that the key predictive targets of CC against CRC were estrogen receptor 2 (ESR2), ATP-binding cassette sub-family G member 2 (ABCG2), breast cancer type 1 susceptibility protein (BRCA1), estrogen receptor 1 (ESR1), cytochrome p450 19A1 (CYP19A1), and epidermal growth factor receptor (EGFR). Visual analysis revealed that the biological processes of CC against CRC were positively linked to hormonal metabolism, regulation of genes, transport, cell communication, and signal transduction. Further, the interrelated molecular pathways were chiefly related to endogenous nuclear estrogen receptor alpha network, forkhead box protein A1 (FOXA1) transcription factor network, activating transcription factor 2 (ATF2) transcription factor network, regulation of telomerase, plasma membrane estrogen receptor signaling, estrogen biosynthesis, androgen receptor, FOXA transcription factor networks, estrogen biosynthesis, and phosphorylation of repair proteins. CONCLUSIONS Use of system pharmacology revealed the biotargets, biological processes, and pharmacological pathways of CC against CRC. Intriguingly, the identifiable predictive biomolecules are likely potential targets for effectively treating CRC.

BRD4 Inhibitor AZD5153 Suppresses the Proliferation of Colorectal Cancer Cells and Sensitizes the Anticancer Effect of PARP Inhibitor

Background: Bromodomain-containing protein 4(BRD4) is reported to play a vital role in the development of numerous malignant diseases, which is considered as a promising target for cancer therapy. AZD5153, a novel specific BRD4 inhibitor, showed potent anticancer effects in several cancer types, but its therapeutic potential has not been fully evaluated in colorectal cancer cells. Objective: We sought to evaluate the therapeutic potential of BRD4 inhibition of by AZD5153 and its combined anticancer cancer effect with PARP inhibitor BMN673 in vitro and in vivo in colorectal cancer. Methods: We analyzed The Cancer Genome Atlas (TCGA) database to investigate BRD4 expression in colorectal cancer patient. Clonogenic assays 、MTT assays and PI/Annexin V staining were used to determine the effect of AZD5153 and BMN673 and combination therapy on cell viability and apoptosis induction. Western blotting was applied to detect relevant molecules changes. Propidium iodide staining was performed to examine cell cycle distributions after monotherapy or combination therapy. Nude mice xenograft model was generated to confirm the therapeutic effect of AZD5153 and BMN673 combination in vivo, and IHC staining was used to detect the expression level of BRD4 and related markers in colorectal patient and xenograft. Results: Analysis of TCGA database indicated that BRD4 was overexpressed in colorectal cancer patient. The clonogenic and MTT assays and PI/Annexin V staining demonstrated that AZD5153 significantly suppressed cell proliferation and induced apoptosis in colorectal cancer cells HCT116 and LoVo. Western blotting showed that AZD5153 inhibited the expression of c-Myc and increased expression of the apoptosis markers, cleaved caspase-3 and poly(ADP-ribose) polymerase (PARP), besides, we found that BRD4 knockdown could also inhibited cell proliferation and induced cell apoptosis. Moreover, AZD5153 inhibited the expression of Wee1 and impaired G2M cell cycle checkpoint, thus sensitized the anticancer effect of BMN673 in vitro and in vivo. Conclusion: Our data revealed that AZD5153suppressed the proliferation of colorectal cancer cells and sensitized them to the anticancer effect of the PARP inhibitor BMN673 via Wee1 inhibition in vitro and in vivo. This suggested that targeting BRD4 might be a valuable strategy for colorectal cancer treatment.

Opportunities and challenges of co-targeting epidermal growth factor receptor and autophagy signaling in non-small cell lung cancer

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are a standard therapy for patients with non-small cell lung cancer (NSCLC) with sensitive mutations. However, acquired resistance emerges following a median of 6-12 months. Several studies demonstrated that EGFR-TKI-induced tumor microenvironment stresses and autophagy are important causes of resistance. The current review summarizes the molecular mechanisms involved in EGFR-mediated regulation of autophagy. The role of autophagy in EGFR-TKI treatment, which may serve a role in protection or cell death, was discussed. Furthermore, co-inhibiting EGFR and autophagy signaling as a rational therapeutic strategy in the treatment of patients with NSCLC was explored.

The Interplay of Autophagy and Tumor Microenvironment in Colorectal Cancer-Ways of Enhancing Immunotherapy Action

Autophagy as a primary homeostatic and catabolic process is responsible for the degradation and recycling of proteins and cellular components. The mechanism of autophagy has a crucial role in several cellular functions and its dysregulation is associated with tumorigenesis, tumor-stroma interactions, and resistance to cancer therapy. A growing body of evidence suggests that autophagy is also a key regulator of the tumor microenvironment and cellular immune response in different types of cancer, including colorectal cancer (CRC). Furthermore, autophagy is responsible for initiating the immune response especially when it precedes cell death. However, the role of autophagy in CRC and the tumor microenvironment remains controversial. In this review, we identify the role of autophagy in tumor microenvironment regulation and the specific mechanism by which autophagy is implicated in immune responses during CRC tumorigenesis and the context of anticancer therapy.

miR-20a inhibits hypoxia-induced autophagy by targeting ATG5/FIP200 in colorectal cancer

Autophagy is a highly conserved lysosome-mediated protective cellular process in which cytosolic components, including damaged organelles and long-lived proteins, are cleared. Many studies have shown that autophagy was upregulated in hypoxic regions. However, the precise molecular mechanism of hypoxia-induced autophagy in colorectal cancer (CRC) is still elusive. In this study, we found that miR-20a was significantly downregulated under hypoxia in colon cancer cells, and overexpression of miR-20a alleviated hypoxia-induced autophagy. Moreover, miR-20a inhibits the hypoxia-induced autophagic flux by targeting multiple key regulators of autophagy, including ATG5 and FIP200. Furthermore, by dual-luciferase assay we demonstrated that miR-20a directly targeted the 3'-untranslated region of ATG5 and FIP200, regulating their messenger RNA and protein levels. In addition, reintroduction of exogenous ATG5 or FIP200 partially reversed miR-20a-mediated autophagy inhibition under hypoxia. A negative correlation between miR-20a and its target genes is observed in the hypoxic region of colon cancer tissues. Taken together, our findings suggest that hypoxia-mediated autophagy was regulated by miR-20a/ATG5/FI200 signaling pathway in CRC. miR-20a-mediated autophagy defect that might play an important role in hypoxia-induced autophagy during colorectal tumorigenesis.

Co-expression and prognostic significance of putative CSC markers CD44, CD133, wild-type EGFR and EGFRvIII in metastatic colorectal cancer

The presence of colorectal cancer stem cells (CSCs) have been associated with tumour initiation and resistance to therapy. This study investigated the co-expression and prognostic significance of the CSCs biomarkers CD44 and CD133 with wild-type EGFR (wtEGFR) and EGFRvIII in colorectal cancer (CRC). The expression of these biomarkers were determined in tumours from 70 patients with metastatic CRC by immunohistochemistry, and in a panel of human CRC cell lines, and their variants with acquired-resistance to EGFR inhibitors, by flow cytometry. The expression of CD44, CD133, wtEGFR and EGFRvIII were present in 17%, 23%, 26% and 13% of cases and the co-expression of CD44/CD133 with wtEGFR and EGFRvIII were present in 9% and 3% of the cases respectively. Only co-expression of CSCs/EGFRvIII (P = 0.037), and amphiregulin (P = 0.017) were associated with worse overall survival. Interestingly, disease-free survival was improved in BTC expressing patients (P = 0.025). In vitro CD133 expression and its co-expression with CD44 were associated with primary-resistance to irinotecan and acquired-resistance to anti-EGFR inhibitors respectively. Our results suggest co-expression of CSCs and EGFRvIII could be potential biomarkers of worse overall survival and resistance to therapy in patients with mCRC and warrants further validation in a larger cohort.

Epigallocatechin-3-gallate inhibits the growth and increases the apoptosis of human thyroid carcinoma cells through suppression of EGFR/RAS/RAF/MEK/ERK signaling pathway

Background

Thyroid cancer is the most common type of endocrine malignancy and the incidence rate is rapidly increasing worldwide. Epigallocatechin-3-gallate (EGCG) could suppress cancer growth and induce apoptosis in many types of cancer cells. However, the mechanism of action of EGCG on the growth of human thyroid carcinoma cells has not been fully illuminated.

Methods

Cell proliferation and viability were detected by EdU and MTS assays. Cell cycle distribution was measured by flow cytometry. Migration and invasion were evaluated by scratch and transwell assays. Apoptotic levels were detected by TUNEL staining and western blotting. The protein levels of EGFR/RAS/RAF/MEK/ERK signaling pathway were detected by western blotting. The in vivo results were determined by tumor xenografts in nude mice. The in vivo proliferation, tumor microvessel density, and apoptosis were detected by immunohistochemistry.

Results

EGCG inhibited the proliferation, viability, and cell cycle progression in human thyroid carcinoma cells. EGCG decreased the migration and invasion, but increased the apoptosis of human thyroid carcinoma cells. EGCG reduced the protein levels of phospho (p)-epidermal growth factor receptor (EGFR), H-RAS, p-RAF, p-MEK1/2, and p-extracellular signal-regulated protein kinase 1/2 (ERK1/2) in human thyroid carcinoma cells. EGCG inhibited the growth of human thyroid carcinoma xenografts by inducing apoptosis and down-regulating angiogenesis.

Conclusions

EGCG could reduce the growth and increase the apoptosis of human thyroid carcinoma cells through suppressing the EGFR/RAS/RAF/MEK/ERK signaling pathway. EGCG can be developed as an effective therapeutic agent for the treatment of thyroid cancer.

Exploiting Nanomaterial-mediated Autophagy for Cancer Therapy

Autophagy is a conserved process that is critical for sequestering and degrading proteins, damaged or aged organelles, and for maintaining cellular homeostasis under stress conditions. Despite its dichotomous role in health and diseases, autophagy usually promotes growth and progression of advanced cancers. In this context, clinical trials using chloroquine and hydroxychloroquine as autophagy inhibitors have suggested that autophagy inhibition is a promising approach for treating advanced malignancies and/or overcoming drug resistance of small molecule therapeutics (i.e., chemotherapy and molecularly targeted therapy). Efficient delivery of autophagy inhibitors may further enhance the therapeutic effect, reduce systemic toxicity, and prevent drug resistance. As such, nanocarriers-based drug delivery systems have several distinct advantages over free autophagy inhibitors that include increased circulation of the drugs, reduced off-target systemic toxicity, increased drug delivery efficiency, and increased solubility and stability of the encapsulated drugs. With their versatile drug encapsulation and surface-functionalization capabilities, nanocarriers can be engineered to deliver autophagy inhibitors to tumor sites in a context-specific and/or tissue-specific manner. This review focuses on the role of nanomaterials utilizing autophagy inhibitors for cancer therapy, with a focus on their applications in different cancer types.

The PEAK1-PPP1R12B axis inhibits tumor growth and metastasis by regulating Grb2/PI3K/Akt signalling in colorectal cancer

Pseudopodium enriched atypical kinase 1 (PEAK1), a novel non-receptor tyrosine kinase, was recently implicated in cancer pathogenesis. However, its functional role in colorectal cancer (CRC) is not well known. Herein, we demonstrated that PEAK1 was frequently downregulated in CRC and significantly associated with tumor size, differentiation status, metastasis, and clinical stage. PEAK1 overexpression suppressed CRC cell growth, invasion, and metastasis in vitro and in vivo, whereas knockout had the opposite effects. Further evaluation revealed that PEAK1 expression was positively correlated with protein phosphatase 1 regulatory subunit 12B (PPP1R12B) in CRC cell lines and clinical tissues, and this protein was found to suppress activation of the Grb2/PI3K/Akt pathway. Moreover, PPP1R12B knockdown markedly abrogated PEAK1-mediated tumor suppressive effects, whereas its upregulation recapitulated the effects of PEAK1 knockout on cell behaviours and the activation of signalling. Mechanistically, PI3K and Akt inhibitors reversed impaired the effect of PEAK1 function on cell proliferation, migration, and invasion. Our results provide compelling evidence that the PEAK1-PPP1R12B axis inhibits colorectal tumorigenesis and metastasis through deactivation of the Grb2/PI3K/Akt pathway, which might provide a novel therapeutic strategy for CRC treatment.

Upgraded role of autophagy in colorectal carcinomas

Autophagy is a basic catabolic process closely associated with degradation of cellular components. The role of autophagy in colorectal cancer (CRC) remains controversial. The mechanism of autophagy has been identified as protecting mechanism against tumorigenesis by isolation of damaged organelles or as cytoprotective provides energy in hypoxic regions of CRC tumors. Mutations in proto-oncogenes, such as RAS and BRAF, have been associated with autophagy initiation through signaling pathways of BRAF/MEK/ERK and PI3K/AKT/mTOR. A combination therapy of chemotherapeutic agents and autophagy inhibitors such as hydroxychloroquine or immunotherapy might represent a major step that could be evaluated as a putative novel therapeutic strategy in CRC patients.

The role of autophagy in the treatment of BRAF mutant colorectal carcinomas differs based on microsatellite instability status

Autophagy has been identified as a catabolic mechanism in cells but its' role in cancer remains controversial. Autophagy has been characterized either as tumor suppressor or inducer mechanism in many tumor types. Monoclonal antibodies against EGFR (cetuximab and panitumumab) represent a major step in the treatment of mCRC. Several studies propose that cetuximab and panitumumab trigger autophagy which reveals a potential resistance mechanism to these agents. The last years immunotherapy appears to be a novel promising strategy for the treatment of patients with solid tumors, including colorectal cancer. Checkpoint inhibitors, such as anti-PD1 (nivolumab and pembrolizumab) and anti-CTLA-4 (ipilimumab) antibodies have already been developed and applied in mCRC patients with MSI-H phenotype. The association between mtBRAF and autophagy or MSI status has already been characterized. In our study, we identify the autophagy initiation through anti-EGFR monoclonal antibodies and checkpoint inhibitors in colorectal carcinoma cell lines according to microsatellite status. The combination of autophagy inhibition, anti-EGFR antibodies and checkpoint inhibitors as well as autophagy targeting, MEK inhibition and anti-EGFR antibodies or checkpoint inhibitors appears to be the best treatment approach for microsatellite instability high and stable colorectal cancer cell lines, respectively. Both combinatorial approaches reduce cell viability through the induction of apoptotic cell death. The findings of this study point out the importance of different approach for the treatment of BRAF mutant metastatic colorectal cancers based on their microsatelite instability phenotype.