Regorafenib induces adaptive resistance of colorectal cancer cells via inhibition of vascular endothelial growth factor receptor

Regorafenib Induces Senescence and Epithelial-Mesenchymal Transition in Colorectal Cancer to Promote Drug Resistance

Potential intrinsic resistance mechanisms to regorafenib were explored after short exposure (3 days) on five CRC cell lines (HCT-116, SW1116, LS-1034, SW480, Caco-2). The observation of senescence-like features led to the investigation of a drug-initiated phenotype switch. Following long-term exposure (12 months) of HCT-116 and SW480 cell lines to regorafenib, we developed resistant models to explore acquired resistance. SW480 cells demonstrated senescent-like properties, including a cell arrest in the late G2/prophase cell cycle stage and a statistically significant decrease in the expression of G1 Cyclin-Dependent Kinase inhibitors and key cell cycle regulators. A specific senescence-associated secretome was also observed. In contrast, HCT-116 treated cells presented early senescent features and developed acquired resistance triggering EMT and a more aggressive phenotype over time. The gained migration and invasion ability by long-exposed cells was associated with the increased expression level of key cellular and extracellular EMT-related factors. The PI3K/AKT pathway was a significant player in the acquired resistance of HCT-116 cells, possibly related to a PI3KCA mutation in this cell line. Our findings provide new insights into the phenotypic plasticity of CRC cells able, under treatment pressure, to acquire a stable TIS or to use an early senescence state to undergo EMT.

Platelet-derived growth factor (PDGF) cross-signaling via non-corresponding receptors indicates bypassed signaling in colorectal cancer

Platelet-derived growth factor (PDGF) signaling, besides other growth factor-mediated signaling pathways like vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF), seems to play a crucial role in tumor development and progression. We have recently provided evidence for upregulation of PDGF expression in UICC stage I-IV primary colorectal cancer (CRC) and demonstrated PDGF-mediated induction of PI3K/Akt/mTOR signaling in CRC cell lines. The present study sought to follow up on our previous findings and explore the alternative receptor cross-binding potential of PDGF in CRC. Our analysis of primary human colon tumor samples demonstrated upregulation of the PDGFRβ, VEGFR1, and VEGFR2 genes in UICC stage I-III tumors. Immunohistological analysis revealed co-expression of PDGF and its putative cross-binding partners, VEGFR2 and EGFR. We then analyzed several CRC cell lines for PDGFRα, PDGFRβ, VEGFR1, and VEGFR2 protein expression and found these receptors to be variably expressed amongst the investigated cell lines. Interestingly, whereas Caco-2 and SW480 cells showed expression of all analyzed receptors, HT29 cells expressed only VEGFR1 and VEGFR2. However, stimulation of HT29 cells with PDGF resulted in upregulation of VEGFR1 and VEGFR2 expression despite the absence of PDGFR expression and mimicked the effect of VEGF stimulation. Moreover, PDGF recovered HT29 cell proliferation under simultaneous treatment with a VEGFR or EGFR inhibitor. Our results provide some of the first evidence for PDGF cross-signaling through alternative receptors in colorectal cancer and support anti-PDGF therapy as a combination strategy alongside VEGF and EGF targeting even in tumors lacking PDGFR expression.

Establishment of a 3D model of tumor-driven angiogenesis to study the effects of anti-angiogenic drugs on pericyte recruitment

Hepatocellular carcinoma (HCC), as a well-vascularized tumor, has attracted increasing attention in antiangiogenic therapies. Notably, emerging studies reveal that the long-term administration of antiangiogenic drugs induces hypoxia in tumors. Pericytes, which play a vital role in vascular stabilization and maturation, have been documented to be associated with antiangiogenic drug-induced tumor hypoxia. However, the role of antiangiogenic agents in regulating pericyte behavior still remains elusive. In this study, by using immunostaining analysis, we first demonstrated that tumors obtained from HCC patients were highly angiogenic, in which vessels were irregularly covered by pericytes. Therefore, we established a new 3D model of tumor-driven angiogenesis by culturing endothelial cells, pericytes, cancer stem cells (CSCs) and mesenchymal stem cells (MSCs) with microcarriers in order to investigate the effects and mechanisms exerted by antiangiogenic agents on pericyte recruitment during tumor angiogenesis. Interestingly, microcarriers, as supporting matrices, enhanced the interactions between tumor cells and the extracellular matrix (ECM), promoted malignancy of tumor cells and increased tumor angiogenesis within the 3D model, as determined by qRT-PCR and immunostaining. More importantly, we showed that zoledronic acid (ZA) reversed the inhibited pericyte recruitment, which was induced by sorafenib (Sora) treatment, through fostering the expression and activation of ErbB1/ErbB2 and PDGFR-β in pericytes, in both an in vitro 3D model and an in vivo xenograft HCC mouse model. Hence, our model provides a more pathophysiologically relevant platform for the assessment of therapeutic effects of antiangiogenic compounds and identification of novel pharmacological targets, which might efficiently improve the benefits of antiangiogenic treatment for HCC patients.

Integration of transcriptomics and metabolomics reveals anlotinib-induced cytotoxicity in colon cancer cells

BACKGROUND

Mounting evidences suggested that anlotinib exhibits effective anti-tumor activity in various cancer types, such as lung cancer, glioblastoma and medullary thyroid cancer. However, its function in colon cancer remains to be further revealed.

METHODS

Colon cancer cells (HCT-116) were treated with or without anlotinib. Transcript and metabolite data were generated through RNA sequencing and liquid chromatography-tandem mass spectrometry, respectively. The integrated analysis transcriptomics and metabolomics was conducted using R programs and online tools, including ClusterProfiler R program, GSEA, Prognoscan and Cytoscape.

RESULTS

We found that differentially expressed genes (DEGs) were mainly involved in metabolic pathways and ribosome pathway. Structural maintenance of chromosome 3 (SMC3), Topoisomerase II alpha (TOP2A) and Glycogen phosphorylase B (PYGB) are the most significant DEGs which bring poor clinical prognosis in colon cancer. The analysis of metabolomics presented that most of the differentially accumulated metabolites (DAMs) were amino acids, such as L-glutamine, DL-serine and aspartic acid. The joint analysis of DEGs and DAMs showed that they were mainly involved in protein digestion and absorption, ABC transporters, central carbon metabolism, choline metabolism and Gap junction. Anlotinib affected protein synthesis and energy supporting of colon cancer cells by regulating amino acid metabolism.

CONCLUSIONS

Anlotinib has a significant effect on colon cancer in both transcriptome and metabolome. Our research will provide possible targets for colon cancer treatment using anlotinib.

A small natural molecule CADPE kills residual colorectal cancer cells by inhibiting key transcription factors and translation initiation factors

Residual disease is the major cause for colorectal cancer (CRC) relapse. Herein, we explore whether and how a natural molecule CADPE killed heterogenic populations in a panel of CRC cell lines with KRAS/BRAF mutations that are natively resistant to EGFR- or VEGFR-targeted therapy, without sparing persistent cells, a reservoir of the disease relapse. Results showed that CADPE killed the tumor bulk and residual cells in the panel of CRC cell lines, rapidly inactivated c-Myc, STAT3, and NF-κB, and then decreased the protein levels of key signaling molecules for CRC, such as β-catenin, Notch1, and the nodes of mTOR pathways; eukaryotic translation initiation factors (eIF4F); anti-apoptotic proteins (Bcl-xl, Mcl-1, and survivin); and stemness-supporting molecules (CD133, Bim-1, and VEGF). In terms of mechanism of action, concurrent downregulation of Mcl-1, Bcl-xl, and survivin was necessary for CADPE to kill CRC bulk cells, while additional depletion of CD133 and VEGF proteins was required for killing the residual CRC cells. Moreover, the disabled c-Myc, STAT3, NF-κB, and eIF4F were associated with the broadly decreased levels of anti-apoptosis proteins and pro-stemness proteins. Consistently, CADPE suppressed CRC tumor growth associated with robust apoptosis and depleted levels of c-Myc, STAT3, NF-κB, eIF4F, anti-apoptotic proteins, and pro-stemness proteins. Our findings showed the promise of CADPE for treating CRC and suggested a rational polytherapy that disables c-Myc, STAT3, NF-κB, and eIF4F for killing CRC residual disease.

Protein kinase inhibitor-based cancer therapies: Considering the potential of nitric oxide (NO) to improve cancer treatment

The deregulation of a wide variety of protein kinases is associated with cancer cell initiation and tumor progression. Owing to their indispensable function in signaling pathways driving malignant cell features, protein kinases constitute major therapeutic targets in cancer. Over the past two decades, intense efforts in drug development have been dedicated to this field. The development of protein kinase inhibitors (PKIs) have been a real breakthrough in targeted cancer therapy. Despite obvious successes across patients with different types of cancer, the development of PKI resistance still prevails. Combination therapies are part of a comprehensive approach to address the problem of drug resistance. The therapeutic use of nitric oxide (NO) donors to bypass PKI resistance in cancer has never been tested in clinic yet but several arguments suggest that the combination of PKIs and NO donors may exert a potential anticancer effect. The present review summarized the current state of knowledge on common targets to both PKIs and NO. Herein, we attempt to provide the rationale underlying a potential combination of PKIs and NO donors for future directions and design of new combination therapies in cancer.

ADIPOSE TISSUE AND ITS ROLE IN MICROENVIRONMENT OF THE COLORECTAL ADENOCARCINOMA CANCER CELL

Introduction. The mechanisms of adipose-tissue’s influence on tumor progression has been studied a lot, but the way of interaction of adipocytes with tumor cells have not been well defined until now. Objective. The aim of this study was to evaluate the mechanisms of adipocytes and tumor cells interaction under the influence of radiation and chemo-radiation therapy in locally advanced rectal cancer (LARC) patients. Material and methods. A prospective randomized single-center study was conducted. It involved 110 patients with LARC and pre-obesity. The patients were randomized into a main group A (radiation therapy and oxaliplatin-based chemotherapy) and a comparison group B (radiation therapy and fluoropyrimidine-based mono-chemotherapy). Superoxide free radicals and NO levels generated by mitochondria of adipocytes were evaluated In both groups’. Also, there was estimated the indices of MMP-2, MMP-9, 8-oxoG, and free fatty acids (FFA) level. Results and discussion. Level of superoxide radicals in tumor-adjacent adipose tissue was 0.58±0.15 (main group) and 0.70±0.12 nmol/g·min (comparison group) (p<0.001). Blood levels of FFA increased in group A up to 2.05±0.15, and in group B up to 2.48±0.20 mmol/l (while in it was 0.57±0.11 mmol/L). 8-oxoG levels in tumor-adjacent adipose tissue had no statistically significant differences. Conclusions. The tumor-adjacent adipose tissue is an energy depot that can act as a promoter of tumor progression supplying the locally advanced rectal cancer with an energy substrate FFA.  It has been established that the level MMP-2 activity significantly reduces the degree of intercellular matrix remodeling by the XELOX chemotherapy.

Growth suppression of colorectal cancer expressing S492R EGFR by monoclonal antibody CH12

Colorectal cancer (CRC) is a common malignant tumor in the digestive tract, and 30%-85% of CRCs express epidermal growth factor receptors (EGFRs). Recently, treatments using cetuximab, also named C225, an anti-EGFR monoclonal antibody, for CRC have been demonstrated to cause an S492R mutation in EGFR. However, little is known about the biological function of S492R EGFR. Therefore, we attempted to elucidate its biological function in CRC cells and explore new treatment strategies for this mutant form. Our study indicated that EGFR and S492R EGFR accelerate the growth of CRC cells in vitro and in vivo and monoclonal antibody CH12, which specifically recognizes an EGFR tumor-specific epitope, can bind efficiently to S492R EGFR. Furthermore, mAb CH12 showed significantly stronger growth suppression activities and induced a more potent antibody-dependent cellular cytotoxicity effect on CRC cells bearing S492R EGFR than mAb C225. mAb CH12 obviously suppressed the growth of CRC xenografts with S492R EGFR mutations in vivo. Thus, mAb CH12 may be a promising therapeutic agent in treating patients with CRC bearing an S492R EGFR mutation.

Metabolic profiling of the anti-tumor drug regorafenib in mice

Regorafenib is a novel tyrosine kinase inhibitor, which has been approved by the United States Food and Drug Administration for the treatment of various tumors. The purpose of the present study was to describe the metabolic map of regorafenib, and investigate its effect on liver function. Mass spectrometry-based metabolomics approach integrated with multiple mass defect filter was used to determine the metabolites of regorafenib in vitro incubation mixtures (human liver microsomes and mouse liver microsomes), serum, urine and feces samples from mice treated with 80 mg/kg regorafenib. Eleven metabolites including four novel metabolites were identified in the present investigation. As halogen substituted drug, reductive defluorination and oxidative dechlorination metabolites of regorafenib were firstly report in present study. By screening using recombinant cytochrome P450 s (CYPs), CYP3A4 was found to be the principal isoforms involved in regorafenib metabolism. The predication with a molecular docking model confirmed that regorafenib had potential to interact with the active sites of CYP3A4, CYP3A5 and CYP2D6. Serum chemistry analysis revealed no evidence of hepatic damage from regorafenib exposure. This study provided a global view of regorafenib metabolism and its potential side-effects.

The Aquaporin 1 Inhibitor Bacopaside II Reduces Endothelial Cell Migration and Tubulogenesis and Induces Apoptosis

Expression of aquaporin-1 (AQP1) in endothelial cells is critical for their migration and angiogenesis in cancer. We tested the AQP1 inhibitor, bacopaside II, derived from medicinal plant Bacopa monnieri, on endothelial cell migration and tube-formation in vitro using mouse endothelial cell lines (2H11 and 3B11) and human umbilical vein endothelial cells (HUVEC). The effect of bacopaside II on viability, apoptosis, migration and tubulogenesis was assessed by a proliferation assay, annexin-V/propidium iodide flow cytometry, the scratch wound assay and endothelial tube-formation, respectively. Cell viability was reduced significantly for 2H11 at 15 μM (p = 0.037), 3B11 at 12.5 μM (p = 0.017) and HUVEC at 10 μM (p < 0.0001). At 15 μM, the reduced viability was accompanied by an increase in apoptosis of 38%, 50% and 32% for 2H11, 3B11 and HUVEC, respectively. Bacopaside II at ≥10 μM significantly reduced migration of 2H11 (p = 0.0002) and 3B11 (p = 0.034). HUVECs were most sensitive with a significant reduction at ≥7.5 μM (p = 0.037). Tube-formation was reduced with a 15 μM dose for all cell lines and 10 μM for 3B11 (p < 0.0001). These results suggest that bacopaside II is a potential anti-angiogenic agent.