CD44 protein levels and its biological activity are regulated in Balb/c 3T3 fibroblasts by serum factors and by transformation with the ras but not with the sis oncogene

Enzymatically cross-linked hyaluronic acid hydrogels as in situ forming carriers of platelet-rich plasma: Mechanical properties and bioactivity levels evaluation

New studies have shown the great potential of the combination of in situ enzymatically cross-linked hydrogels based on tyramine derivative of hyaluronic acid (HA-TA) with platelet-rich plasma (PRP) and platelet lysate in regenerative medicine. This study describes how the presence of PRP and platelet lysate affects the kinetics of gelation, viscoelastic properties, swelling ratio, and the network structure of HA-TA hydrogels and how the encapsulation of PRP in hydrogels affects the bioactivity of released PRP determined as the ability to induce cell proliferation. The properties of hydrogels were tuned by a degree of substitution and concentration of HA-TA derivatives. The addition of platelet derivatives to the reaction mixture slowed down the cross-linking reaction and reduced elastic modulus (G') and thus cross-linking efficiency. However, low-swellable hydrogels (7-190%) suitable for soft tissue engineering with G' 200-1800 Pa were prepared with a gelation time within 1 min. It was confirmed that tested cross-linking reaction conditions are suitable for PRP incorporation because the total bioactivity level of PRP released from HA-TA hydrogels was ≥87% and HA-TA content in the hydrogels and thus mesh size (285-482 nm) has no significant effect on the bioactivity level of released PRP.

The synthesis and comparison of chondroitin sulfate-modified PDMAEMA with chondroitin sulfate-modified PEI as a potential gene delivery vector

CS-PDMAEMA obtained by reacting HS-PDMAEMA with CSMA via Michael addition, shows lower cytotoxicity and better transfection efficiency than PDMAEMA. The transfection efficiency is higher in 3T3 cells than in U87 cells owing to higher expression of ASGP-R.

Tailored doxorubicin-hyaluronan conjugate as a potent anticancer glyco-drug: an alternative to prodrug approach

Releasibility of doxorubicin from drug-conjugates is believed to be a prerequisite for its anti-cancer activity. Here, a new glyco-drug approach that circumvents the releasibility restriction is reported, opening a new possibility to design efficient, target specific drug delivery system. It is discovered that stable amide coupling of doxorubicin (DOX) tohyaluronan (HA) shows dose dependent cytotoxicity to CD44 positive human coloncancer cells (HCT116) as compared to human breast cancer cells(MCF-7) and mouse fibroblast cells (NIH-3T3), which express less CD44 receptor. This direct conjugation approach is an easy scalable strategy that could be adopted to design innocuous anti-tumor nanoparticle formulations.

Malignant peripheral nerve sheath tumor cell invasion is facilitated by Src and aberrant CD44 expression

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive malignancies that arise within peripheral nerves. These tumors occur with increased incidence in patients with neurofibromatosis type 1 (NF1), exhibiting increased Ras activity due to loss of the NF1 gene product, neurofibromin, and abnormal expression of the epidermal growth factor receptor (EGFR). We previously found that MPNSTs express increased levels of the CD44 family of transmembrane glycoproteins that have been implicated in tumor cell invasion and metastasis. In two MPNST cell lines, we have found that elevated CD44 expression and cell invasion are dependent on Src kinase activity but are independent of mitogen-activated protein kinases (MAPK) kinase (MEK) activity. In contrast, inhibition of Src kinase activity has no influence on MPNST cell proliferation. Reduction of CD44 levels, using antisense oligonucleotides, results in reduced MPNST cell invasion in vitro, suggesting that Src contributes in part to MPNST cell invasion by increasing CD44 levels. At least some of this increased CD44 expression results from elevated EGFR levels through a Src-dependent mechanism, consistent with the notion that EGFR promotes constitutive Src activation in MPNSTs. These data indicate that Src and CD44 are putative targets for the treatment of MPNST invasion and metastasis.

CD44 mediates constitutive type I receptor signaling in cervical carcinoma cells

OBJECTIVE

The CD44 transmembrane glycoprotein family has been implicated in the growth and metastasis of numerous human cancers. CD44 may function in some cells through interactions with type I receptor tyrosine kinases, including erbB2. Here, we tested whether CD44 interacts with erbB2 and another type I receptor, the epidermal growth factor receptor (EGFR), in human cervical carcinoma tissues and cell lines and whether these interactions influence erbB2 signaling.

METHODS

CD44, EGFR, and erbB2 colocalization were examined in 36 pT1b-pT2b cervical cancer cases and in the CaSki and SiHa cervical carcinoma cell lines by immunohistochemistry and laser scanning confocal microscopy. The role of CD44-EGFR-erbB2 interactions in erbB2 signaling was examined by immunoprecipitation and using antisense CD44 oligonucleotides.

RESULTS

CD44, erbB2, and EGFR coexpression and colocalization were observed in 42% (15/36) of cervical carcinoma cases and in both cervical carcinoma cell lines. Colocalization occurred to an equivalent extent in all tumor grades examined. CD44 coimmunoprecipitated with erbB2 and EGFR in cervical carcinoma cell lysates, indicating that these proteins interact with each other. Reduction of CD44 expression inhibited constitutive erbB2 activity. High CD44 expression was linked to EGFR activity using dominant negative EGFR, suggesting that type I receptors may autoregulate their activity in these cells.

CONCLUSIONS

Our data indicate that CD44 can mediate type I receptor function in cervical carcinoma cells that overexpress both CD44 and either erbB2 or EGFR and suggest a novel mechanism by which these proteins may contribute to cervical carcinoma tumor growth and metastasis.

Gene expression profile in prion protein-deficient fibroblasts in culture

To investigate the physiological function of the cellular isoform of prion protein (PrP(C)), the gene expression profile was studied by analyzing a cDNA expression array containing 597 clones of various functional classes in two distinct skin fibroblast cell lines designated SFK and SFH, established from PrP-deficient (PrP(-)(/-)) mice and PrP(+/+) mice, respectively. The cells were incubated in the culture medium with or without inclusion of basic fibroblast growth factor (bFGF). When SFK cells were compared with SFH cells in untreated conditions, the expression of 15 genes, including those essential for cell proliferation and adhesion, was reduced, whereas the expression of 27 genes, including those involved in the insulin-like growth factor-I (IGF-I) signaling pathway, was elevated. Northern blot analysis verified a significant down-regulation of the receptor tyrosine kinase substrate Eps8, cyclin D1, and CD44 mRNAs, and a substantial up-regulation of phosphatidylinositol 3-kinase p85, IGF-I, and serine protease inhibitor-2.2 mRNAs in SFK cells. The patterns of induction or reduction of gene expression after exposure to bFGF showed considerable overlap between both cell types. Furthermore, both Eps8 and CD44 mRNA levels were reduced greatly in the brain tissues of the cerebrum isolated from the PrP(-)(/-) mice. These results indicate that the disruption of the PrP gene resulted in an aberrant regulation of a battery of genes important for cell proliferation, differentiation, and survival, including those located in the Ras and Rac signaling pathways.

In vitro analysis of transformation potential associated with retroviral vector insertions

While replication-defective retroviral vectors provide excellent vehicles for the long-term expression of therapeutic genes, they also harbor the potential to induce undesired genetic changes by random insertions into the host genome. The rate of insertional mutagenesis for retroviral vectors has been determined in several different assay systems; however, the rate at which such events induce cellular transformation has not been directly determined. Such measurements are critical to determining the actual risk of carcinogenesis resulting from retroviral gene therapy. In this study, the ability of a replication-defective retroviral vector, GlnBgSvNa, to induce cellular transformation in the BALB/c-3T3 in vitro transformation assay was assessed. The transformation frequency observed in vector-transduced BALB/c-3T3 cells, which contained one to six copies of integrated provirus, was not significantly different from that of untreated control cells. The finding that GlnBgSvNa was nontransforming in this assay indicates that the rate of transformation induced by retroviral insertions is less than the spontaneous rate of cellular transformation by BALB/c-3T3 cells, or less than 1.1 x 10(-5). These results are the first to define an upper limit for the rate of transformation induced by retroviral vectors.

CD44 cell adhesion molecules

The CD44 proteins form a ubiquitously expressed family of cell surface adhesion molecules involved in cell-cell and cell-matrix interactions. The multiple protein isoforms are encoded by a single gene by alternative splicing and are further modified by a range of post-translational modifications. CD44 proteins are single chain molecules comprising an N-terminal extracellular domain, a membrane proximal region, a transmembrane domain, and a cytoplasmic tail. The CD44 gene has only been detected in higher organisms and the amino acid sequence of most of the molecule is highly conserved between mammalian species. The principal ligand of CD44 is hyaluronic acid, an integral component of the extracellular matrix. Other CD44 ligands include osteopontin, serglycin, collagens, fibronectin, and laminin. The major physiological role of CD44 is to maintain organ and tissue structure via cell-cell and cell-matrix adhesion, but certain variant isoforms can also mediate lymphocyte activation and homing, and the presentation of chemical factors and hormones. Increased interest has been directed at the characterisation of this molecule since it was observed that expression of multiple CD44 isoforms is greatly upregulated in neoplasia. CD44, particularly its variants, may be useful as a diagnostic or prognostic marker of malignancy and, in at least some human cancers, it may be a potential target for cancer therapy. This review describes the structure of the CD44 gene and discusses some of its roles in physiological and pathological processes.

Modulatory proteins and processes in alliance with immune cells, mediators, and extracellular proteins in renal interstitial fibrosis

A synopsis of the many aspects and factors that contribute to renal tubulo-interstitial fibrosis is presented. The role of fibrogenic cytokines and the conversion of fibroblasts to myofibroblasts are described. It is emphasized that oxygen radicals cause fibroblasts to generate collagen. The properties of those accessory modulatory proteins that affect the behavior of cells in the interstitium are considered and how matrix for ensuing fibrosis is laid down. Understanding the extracellular matrix proteins and these modulatory proteins is important because their behavior can now be modified by means of antisense oligonucleotides.

Over-expression of human CD44s in murine 3T3 cells: selection against during primary tumorigenesis and selection for during micrometastasis

Human CD44 standard isoform (hCD44s) cDNA regulated by a high-expressing promoter was transfected into Balb/c 3T3 cells and the tumorigenic and metastatic capacities of the transfectants were investigated in nude mice at the subcutaneous site. One of three transfectants was tumorigenic. hCD44s expression was lost in the cells of large primary tumors using this tumorigenic clone. These tumors were extremely aggressive giving overt metastases and micrometastases to several sites including mesentery, stomach, liver, diaphragm, pancreas and lung. Micrometastatic cells re-expressed hCD44s, consistent with its importance for early steps in the metastatic cascade. hCD44s was not expressed in overt metastases; most probably the expression was lost during the outgrowth of micrometastases into overt metastatic tumors. Thus hCD44s expression in murine 3T3 cells does induce tumorigenicity in select cases, is not compatible with aggressive outgrowth of primary or secondary tumors, and is advantageous for early steps in metastatic spread. These results suggest that CD44s is an example of a novel type of 'metastasis' molecule that is disadvantageous for tumor growth and is only transiently advantageous during metastatic spreading of tumor cells to distant organs.

Overexpressed human CD44s promotes lung colonization during micrometastasis of murine fibrosarcoma cells: facilitated retention in the lung vasculature

Normally nonmetastatic murine sis-transformed BALB/c 3T3 cells, transfected with human CD44s gene (hCD44s), acquire spontaneous metastatic capacity to the lung. The mechanism(s) of this facilitated micrometastasis was analyzed in an experimental metastasis model. Human CD44s overexpression promoted the earliest stages severalfold (initial implantation and subsequent stabilization of tumor cells) but was irrelevant for later stages (subsequent outgrowth) of lung experimental micrometastasis. By injecting mixed populations of parental (nonmetastatic) and CD44s-transfected cells, it was shown that cell-cell adhesion between tumor and parental cells was not promoted by hCD44s but that promotion of cell-cell adhesion to lung endothelium or specifically between transfected cells (via hyaluronan) are likely mechanisms. Results obtained with hCD44s-negative primary tumor cells and hCD44s-positive or -negative variants of lung micrometastatic cells (after s.c. injection of transfectants) confirmed the importance of CD44s overexpression for early but not late stages of experimental lung metastasis. Therefore, CD44s represents a metastasis-facilitating molecule that is irrelevant for primary tumor outgrowth but that promotes micrometastasis to the lungs at the very earliest stages.