The metastatic process in breast cancer is related to the expression of the epithelial-to-mesenchymal transition transcription factors (EMT-TFs) SNAIL, SLUG, SIP1 and TWIST1. EMT-TFs and nuclear factor-κB (NF-κB) activation have been associated with aggressiveness and metastatic potential in carcinomas. Here, we sought to examine the role of NF-κB in the aggressive properties and regulation of EMT-TFs in human breast cancer cells. Blocking NF-κB/p65 activity by reducing its transcript and protein levels (through siRNA-strategy and dehydroxymethylepoxyquinomicin [DHMEQ] treatment) in the aggressive MDA-MB-231 and HCC-1954 cell lines resulted in decreased invasiveness and migration, a downregulation of SLUG, SIP1, TWIST1, MMP11 and N-cadherin transcripts and an upregulation of E-cadherin transcripts. No significant changes were observed in the less aggressive cell line MCF-7. Bioinformatics tools identified several NF-κB binding sites along the promoters of SNAIL, SLUG, SIP1 and TWIST1 genes. Through chromatin immunoprecipitation and luciferase reporter assays, the NF-κB/p65 binding on TWIST1, SLUG and SIP1 promoter regions was confirmed. Thus, we suggest that NF-κB directly regulates the transcription of EMT-TF genes in breast cancer. Our findings may contribute to a greater understanding of the metastatic process of this neoplasia and highlight NF-κB as a potential target for breast cancer treatment.
Radiotherapy remains a major approach to adjuvant therapy for patients with advanced colorectal cancer, however, the fractionation schedules frequently allow for the repopulation of surviving tumors cells, neoplastic progression, and subsequent metastasis. The aim of the present study was to analyze the transgenerational effects induced by radiation and evaluate whether it could increase the malignant features on the progeny derived from irradiated parental colorectal cancer cells, Caco-2, HT-29, and HCT-116. The progeny of these cells displayed a differential radioresistance as seen by clonogenic and caspase activation assay and had a direct correlation with survivin expression as observed by immunoblotting. Immunofluorescence showed that the most radioresistant progenies had an aberrant morphology, disturbance of the cell-cell adhesion contacts, disorganization of the actin cytoskeleton, and vimentin filaments. Only the progeny derived from intermediary radioresistant cells, HT-29, reduced the E-cadherin expression and overexpressed β-catenin and vimentin with increased cell migration, invasion, and metalloprotease activation as seen by immunoblotting, wound healing, invasion, and metalloprotease activity assay. We also observed that this most aggressive progeny increased the Wnt/β-catenin-dependent TCF/LEF activity and underwent an upregulation of mesenchymal markers and downregulation of E-cadherin, as determined by qRT-PCR. Our results showed that the intermediate radioresistant cells can generate more aggressive cellular progeny with the EMT-like phenotype. The Wnt/β-catenin pathway may constitute an important target for new adjuvant treatment schedules with radiotherapy, with the goal of reducing the migratory and invasive potential of the remaining cells after treatment.
Collectively, our results demonstrate for the first time that altered N-glycan expression plays an important role in the loss of AJ stability in undifferentiated colorectal cancer cells and that this loss may be associated with the progression of colorectal cancer.
The altered expressions of claudin proteins have been reported during the tumorigenesis of colorectal cancer. However, the molecular mechanisms that regulate these events in this cancer type are poorly understood. Here, we report that epidermal growth factor (EGF) increases the expression of claudin-3 in human colorectal adenocarcinoma HT-29 cells. This increase was related to increased cell migration and the formation of anchorage-dependent and anchorage-independent colonies. We further showed that the ERK1/2 and PI3K-Akt pathways were involved in the regulation of these effects because specific pharmacological inhibition blocked these events. Genetic manipulation of claudin-1 and claudin-3 in HT-29 cells showed that the overexpression of claudin-1 resulted in decreased cell migration; however, migration was not altered in cells that overexpressed claudin-3. Furthermore, the overexpression of claudin-3, but not that of claudin-1, increased the tight junction-related paracellular flux of macromolecules. Additionally, an increased formation of anchorage-dependent and anchorage-independent colonies were observed in cells that overexpressed claudin-3, while no such changes were observed when claudin-1 was overexpressed. Finally, claudin-3 silencing alone despite induce increase proliferation, and the formation of anchoragedependent and -independent colonies, it was able to prevent the EGF-induced increased malignant potential. In conclusion, our results show a novel role for claudin-3 overexpression in promoting the malignant potential of colorectal cancer cells, which is potentially regulated by the EGF-activated ERK1/2 and PI3K-Akt pathways.
Colorectal cancer represents the fourth highest mortality rate among cancer types worldwide. An understanding of the molecular mechanisms that regulate their progression can prevents or reduces mortality due to this disease. Epithelial cells present an apical junctional complex connected to the actin cytoskeleton, which maintains the dynamic properties of this complex, tissue architecture and cell homeostasis. Several studies have indicated that apical junctional complex alterations and actin cytoskeleton disorganization play a critical role in epithelial cancer progression. However, few studies have examined the existence of an interrelation between these 2 components, particularly in colorectal cancer. This review discusses the recent progress toward elucidating the role of alterations of apical junctional complex constituents and of modifications of actin cytoskeleton organization and discusses how these events are interlinked to modulate cellular responses related to colorectal cancer progression toward successful metastasis.
Lithium is a well-established non-competitive inhibitor of glycogen synthase kinase-3β (GSK-3β), a kinase that is involved in several cellular processes related to cancer progression. GSK-3β is regulated upstream by PI3K/Akt, which is negatively modulated by PTEN. The role that lithium plays in cancer is controversial because lithium can activate or inhibit survival signaling pathways depending on the cell type. In this study, we analyzed the mechanisms by which lithium can modulate events related to colorectal cancer (CRC) progression and evaluated the role that survival signaling pathways such as PI3K/Akt and PTEN play in this context. We show that the administration of lithium decreased the proliferative potential of CRC cells in a GSK-3β-independent manner but induced the accumulation of cells in G2/M phase. Furthermore, high doses of lithium increased apoptosis, which was accompanied by decreased proteins levels of Akt and PTEN. Then, cells that were induced to overexpress PTEN were treated with lithium; we observed that low doses of lithium strongly increased apoptosis. Additionally, PTEN overexpression reduced proliferation, but this effect was minor compared with that in cells treated with lithium alone. Furthermore, we demonstrated that PTEN overexpression and lithium treatment separately reduced cell migration, colony formation, and invasion, and these effects were enhanced when lithium treatment and PTEN overexpression were combined. In conclusion, our findings indicate that PTEN overexpression and lithium treatment cooperate to reduce the malignancy of CRC cells and highlight lithium and PTEN as potential candidates for studies to identify new therapeutic approaches for CRC treatment.
Our results demonstrate that PI3K/Akt and GSK-3β prevents in a differential fashion the malignant phenotype of HCT-116 colorectal cancer cells, which could constitute a potential therapeutic target for treatment of this cancer type.
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