Environment-mediated drug resistance is a form of de novo drug resistance that protects tumour cells from the initial effects of diverse therapies. Surviving foci of residual disease can then develop complex and permanent acquired resistance in response to the selective pressure of therapy. Recent evidence indicates that environment-mediated drug resistance arises from an adaptive, reciprocal signalling dialogue between tumour cells and the surrounding microenvironment. We propose that new therapeutic strategies targeting this interaction should be applied during initial treatment to prevent the emergence of acquired resistance.

Environment-mediated drug resistance: a major contributor to minimal residual disease

The tumor microenvironment is a dominant force in multidrug resistance.

The tumor microenvironment in hepatocellular carcinoma: current status and therapeutic targets.

Hepatocellular carcinoma (HCC) is the most common primary malignant tumor that accounts for ~80 % of all liver cancer cases worldwide. It is a multifactorial disease caused by a variety of risk factors and often develops in the background of underlying cirrhosis. A number of cellular phenomena, such as tumor microenvironment, inflammation, oxidative stress, and hypoxia act in concert with various molecular events to facilitate tumor initiation, progression, and metastasis. The emergence of microRNAs and molecular-targeted therapies adds a new dimension in our efforts to combat this deadly disease. Intense research in this multitude of areas has led to significant progress in our understanding of cellular processes and molecular mechanisms that occur during multistage events that lead to hepatocarcinogenesis. In this review, we discuss the current knowledge of HCC, focusing mainly on advances that have occurred during the past 5 years and on the development of novel therapeutics for liver cancer.

Cellular and molecular mechanisms of hepatocellular carcinoma: an update.

The tumor microenvironment has been largely studied as a dynamic system orchestrated by inflammatory cells, including cancer cells, stroma as well as the extracellular matrix. It is useful to describe and predict the phenotypic characteristics of cancer. Furthermore, a better understanding of its interplay with the various aspects of the tumor cells may be utilized for the discovery of novel molecular targets. Liver cancer is considered a model of the relation occurring between the tumor micro-environment and tumor development. The chronic inflammatory status of the liver, sustained by the infection of hepatitis viruses, as well as the production of cytokines and growth factors within the parenchyma, lead to an intricate microenvironment. The identification of novel molecular therapeutic targets may improve the outcome of patients with liver cancer as it remains the third leading cause of cancer death worldwide. In the present study, the tumor microenvironment in hepatocellular carcinoma (HCC) was explored by a review of the literature. Studies on hepatitis virus infections and the consequent chronic inflammatory status were examined. In this context, immune-mediated and/or virus-related molecular mechanisms have been hypothesized as being responsible for liver cancer development. The interlink among HCC microenvironment components, comprising cellular elements, cytokines, growth factors and several proteins is also described together with the role of matrix metalloproteinases in HCC development. Finally, the rationale for targeting tumor-stromal interface is summarized in the context of new therapeutic opportunities.

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The tumor microenvironment in hepatocellular carcinoma (review).

In this study, an enzymatic inactive mutant of GnT-V (delta cGnT-V) was constructed and transfected in SMMC 7721 cell line. Integrin beta1 in delta cGnT-V transfectants (delta c-7721) showed attenuation of the number of beta1-6 GlcNAc branching, whereas those in wtGnT-V transfectants (wt-7721) presented a beta1-6 GlcNAc-rich pattern. High integrin beta1 expression was observed in wt-7721 compared with mock cells (7721 cell transfected with the vector pcDNA3), while transfection of delta cGnT-V decreased the integrin beta1 expression, despite of no significant changes on integrin beta1 mRNA level in these cell lines. Pulse-chase experiment showed that Integrin beta1 in delta c-7721 was prone to quick degradation and its half-life was less than 3 h, on the contrary, the alleviating degradation of beta1 subunit was observed in wt-7721 where the beta1 subunit half-life was about 16 h, meanwhile, the degradation rate of beta1 subunit in mock cells was in between, about 10 h. More effective in promoting cell migration toward fibronectin and invasion through Matrigel was observed in wt-7721 while this was almost suppressed in delta c-7721. Our results suggest that the addition of beta1-6 GlcNAc branching caused more fully glycosylated mature form on integrin beta1 and inhibited beta1 protein degradation. Glycosylation caused by GnT-V directs integrin beta1 stability and more delivery to plasma membrane, subsequently promotes Fn-based cell migration and invasion.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/jcb.21071

Increase in β1‐6 GlcNAc branching caused by N‐acetylglucosaminyltransferase V directs integrin β1 stability in human hepatocellular carcinoma cell line SMMC‐7721

Profilin1 (Pfn1) functions as a tumour suppressor against malignant phenotypes of cancer cells. A minimum level of Pfn1 is critical for the differentiation of human epithelial cells, and its lower expression correlates with the tumourigenesis of breast cancer cells and tissues. However, the molecular mechanisms underlying its anti-tumour action remain largely unknown. In this study, we found that stable expression of ectopic Pfn1 sensitized the breast cancer cell line MDA-MB-468 to apoptosis induced by staurosporine, a widely used natural apoptosis-inducing agent. Pfn1 overexpression could also up-regulate the expression of integrin α5β1, which has been shown to inhibit the transformed phenotype of cancer cells. Furthermore, the Pfn1-facilitated apoptosis induced by staurosporine was blocked in cells attached to a supplementary fibronectin substrate, which serves as a ligand of integrin α5β1. These results suggest that the insufficient fibronectin caused by the integrin α5β1 up-regulation might activate a signalling pathway leading to an increase of cellular apoptosis. Moreover, Pfn1 that primarily functions to promote local superstructure formation involving actin filaments and integrin β1 may contribute to its promotion on apoptosis. Our study indicated a previously uncharacterized role of Pfn1 in mediating staurosporine-inducing apoptosis in breast cancer cells via up-regulating integrin α5β1, and suggested a new target for breast cancer therapy.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1582-4934.2011.01369.x

Profilin1 facilitates staurosporine-triggered apoptosis by stabilizing the integrin β1-actin complex in breast cancer cells.

Integrins may play important roles in many cellular events, such as cell proliferation, differentiation, and apoptosis. We showed previously that overexpression of integrin beta1 inhibits cell proliferation in SMMC-7721 cells. Here we reported that one of the cyclin-dependent kinase (CDK) inhibitors, p27(Kip1) was involved in proliferation-inhibition induced by overexpression of integrin beta1. Overexpression of integrin beta1 upregulated p27(Kip1) at the protein level, but not mRNA level. The knock-down of p27(Kip1) expression restored cell growth in integrin beta1-overexpressing cells. Cycloheximide (Chx) treatment and pulse-chase experiments revealed that overexpression of integrin beta1 prolonged the half-life of p27(Kip1) by inhibiting its degradation. Proteasome inhibitor (MG132) treatment of the cells indicated that proteasome mediated degradation of p27, and Skp2-dependent degradation might be prevented. Overexpression of integrin beta1 decreased Skp2 at mRNA level, which was regulated by cell adhesion and the subsequent adhesion-dependent signaling. Overexpression of integrin beta1 reduced cell adhesion, accordingly, inactivated the phosphoinositide 3-kinase (PI3K) signaling. PI3K inhibitor LY294002 upregulated p27(Kip1) at post-translational level and downregulate Skp2 at mRNA level, which could mimic the effects of integrin beta1 overexpression on p27(Kip1) and Skp2. Together, these results suggested that overexpression of integrin beta1 inhibited cell proliferation by preventing the Skp2-dependent degradation of p27(Kip1) via PI3K pathway.

Overexpression of integrin β1 inhibits proliferation of hepatocellular carcinoma cell SMMC‐7721 through preventing Skp2‐dependent degradation of p27 via PI3K pathway

Podocytes can influence glomerular endothelial cell (GEnC) barrier properties and take part in the development of proteinuria by some molecules. Angiopoietin-like protein 3 (Angptl3), secreted by podocytes, is a member of the angiopoietin-like protein family that has important biological functions in endothelial cells. In our previous studies, we showed that mRNA expression of Angptl3 increased significantly in kidneys of children with minimal change nephrotic syndrome. And the mRNA level of Angptl3 was increased in the glomerulus of adriamycin rats with the development of proteinuria. It was also found that Angptl3 was expressed in the cytoplasm of cultured podocytes. Thus, Angptl3 might influence the biological functions of GEnCs in a paracrine manner. In this study, we found that Angptl3 could increase the permeability of GEnCs and increase the level of protein kinase B phosphorylation in cultured GEnCs in vitro. LY294002, a phosphatidylinositol-3 kinase inhibitor, could prevent the increase of permeability of GEnCs induced by Angptl3. Our results also indicated that the integrin αVβ3 antibody (LM609) could block the Angptl3-induced protein kinase B phosphorylation.

/pdf/angiopoietin-like-protein-3-modulates-barrier-properties-of-1eoc4hmx9y.pdf

Angiopoietin-like protein 3 modulates barrier properties of human glomerular endothelial cells through a possible signaling pathway involving phosphatidylinositol-3 kinase/protein kinase B and integrin αVβ3

Integrins mediate many fundamental cellular processes by binding to components of the extracellular matrix. We showed previously that integrin β1A could inhibit cell proliferation. Integrin β1A stimulated the promoter activity of p21 cip1 and enhanced its transcription in SMMC-7721 cells. In this study, we demonstrated that integrin β1A upregulated p27 kip1 at the post-translational level in SMMC-7721 cells. Our results showed that integrin β1A increased the p27 protein amount, both in cytoplasm and nucleus, but did not affect the p27 mRNA amount. Cycloheximide treatment experiment revealed that the half-life of p27 protein was prolonged in integrin β1A overexpressing cells, indicating that integrin β1A inhibited the degradation of p27 protein. Our data also provided evidence that both the proteasome and calpain were involved in the degradation of p27 protein in SMMC-7721 cells. Integrin β1A decreased the Skp2 expression and repressed the activity of calpain during G1 phase in SMMC-7721 cells. Taken together, these results indicated that integrin β1A might upregulate the protein amount of p27 through repressing Skp2-dependent proteasome degradation and calpain- mediated proteolysis in SMMC-7721 cells.

/pdf/integrin-b1a-upregulates-p27-protein-amount-at-the-post-269ymm7e9z.pdf

Zhengyu Fang

Papers

Increase in β1‐6 GlcNAc branching caused by N‐acetylglucosaminyltransferase V directs integrin β1 stability in human hepatocellular carcinoma cell line SMMC‐7721

Profilin1 facilitates staurosporine-triggered apoptosis by stabilizing the integrin β1-actin complex in breast cancer cells.

Overexpression of integrin β1 inhibits proliferation of hepatocellular carcinoma cell SMMC‐7721 through preventing Skp2‐dependent degradation of p27 via PI3K pathway

Angiopoietin-like protein 3 modulates barrier properties of human glomerular endothelial cells through a possible signaling pathway involving phosphatidylinositol-3 kinase/protein kinase B and integrin αVβ3

Integrin β1A Upregulates p27 Protein Amount at the Post-translational Level in Human Hepatocellular Carcinoma Cell Line SMMC-7721