Differentiation dependent matrix formation (fibronectin and laminin) in an experimental murine rhabdomyosarcoma model

Immunohistochemical analysis for Mdm2 and p53 proteins in methylcholanthrene-induced mouse rhabdomyosarcomas

3-methylcholanthrene (MC)-induced mouse 10 embryonal (ERSs) and 24 pleomorphic rhabdomyosarcomas (PRSs) of the dermis were examined immunohistochemically for nuclear reactivity of Mdm2, p53, and proliferating cell nuclear antigen (PCNA). ERSs were microscopically present in the rhabdium layer of the dermis from 10 to 13 weeks post injection (PI), and PRSs developed from 13 weeks PI. Moderate to marked Mdm2 reactivity was observed in each of the 10 ERSs, and 23 of the 24 PRSs. Moderate to marked p53 reactivity was observed in 5 of the 10 ERSs, and 19 of the 24 PRSs. p53 reactivity increased in PRSs compared with ERSs. The level of Mdm2 expression was significantly higher compared with p53 expression. Discordant Mdm2 overexpression was observed in 5 ERSs and 5 PRSs, and discordant p53 overexpression was observed in 1 PRSs, although co-overexpression of Mdm2 and p53 was observed in 5 ERSs and 18 PRSs. PCNA reactivity significantly increased in PRSs compared with ERSs. These results suggest that Mdm2 overexpression is an important pathogenic event in MC-induced mouse rhabdomyosarcomas, and its expression may be induced by p53-independent pathway.

Immunohistochemical detection of myogenin and p21 in methylcholanthrene-induced mouse rhabdomyosarcomas

3-Methylcholanthrene (MC)-induced 10 embryonal (ERSs) and 24 pleomorphic rhabdomyosarcomas (PRSs) of the dermis in mouse were examined immunohistochemically for myogenin, p21 and proliferating cell nuclear antigen (PCNA) nuclear reactivity and myosin reactivity. ERSs had higher expression of myogenin and p21 compared with that of myosin. PRSs were divided into two groups having high (moderate or marked reactivity; HLM) and low (mild reactivity; LLM) levels of myosin expression. Expression of p21 was higher in HLM-PRSs than in LLM-PRSs. Statistically significant association was observed between myosin and p21 expression in PRSs, but not between myosin and myogenin expression. Myogenin and p21 reactivity were observed in myoblast-like cells, but rarely in multinucleated cells. In ERSs, small undifferentiated myogenic precursor cells were also positive for p21. No difference of PCNA reactivity was observed between HLM-PRSs and LLM-PRSs, although its reactivity was higher in PRSs than in ERSs. The results suggest that myogenin is related to myoblast-like cell differentiation in PRSs and that p21 plays essential roles in myotube formation and myosin expression. In ERSs, p21 may be involved in inhibition of myogenic precursor cell proliferation and differentiation.

Modulation of myogenic differentiation in a human rhabdomyosarcoma cell line by a new derivative of 5-fluorouracil (QF-3602)

The in vitro study of mechanisms involved in drug-induced maturation has made it possible to use differentiation-based therapy in clinical practice. The goal of this new therapy is the development of specific agents to induce cancer cells to stop proliferating and express characteristics of normal cells. Recently, by structural modifications of 5-fluorouracil (5-FU), we synthesized a new pyrimidine acyclonucleoside-like compound, 1-¿[3-(3-chloro-2-hydroxypropoxy)-1-methoxy]propyl¿-5-fluorouracil (QF-3602), which showed in rhabdomyosarcoma cells a low toxicity and time-dependent growth inhibition. In this work, we compared the degree of myogenic differentiation of RD rhabdomyosarcoma (RMS) cells after treatment with QF-3602 and 5-FU. Scanning and transmission electron microscopy (SEM and TEM) and immunocytochemical analyses showed that QF-3602 induced the appearance of myofilaments along the myotube-like giant RD cells, an increase in fibronectin and a decrease in vimentin expression. In contrast, only minor changes were observed with 5-FU. Moreover, polymerase chain reaction (PCR) analyses showed that QF-3602 did not induce overexpression of the mdr 1 gene, a resistance mechanism that frequently appears in classical cytotoxic therapy in these tumors. Compounds obtained by structural modifications of 5-FU may be useful in differentiation therapy as a new approach to the treatment of RMS.

GR-891: a novel 5-fluorouracil acyclonucleoside prodrug for differentiation therapy in rhabdomyosarcoma cells

Differentiation therapy provides an alternative treatment of cancer that overcomes the undesirable effects of classical chemotherapy, i.e. cytotoxicity and resistance to drugs. This new approach to cancer therapy focuses on the development of specific agents designed to selectively engage the process of terminal differentiation, leading to the elimination of tumorigenic cells and recovery of normal cell homeostasis. A series of new anti-cancer pyrimidine acyclonucleoside-like compounds were designed and synthesized by structural modifications of 5-fluorouracil, a drug which causes considerable cell toxicity and morbidity, and we evaluated their applicability for differentiation therapy in human rhabdomyosarcoma cells. We tested the pyrimidine derivative GR-891, (RS)-1-[[3-(2-hydroxyethoxy)-1-isopropoxy]propyl]-5-fluorouracil, an active drug which shows low toxicity in vivo and releases acrolein which is an aldehyde with anti-tumour activity. Both GR-891 and 5-fluorouracil caused time- and dose-dependent growth inhibition in vitro; however, GR-891 showed no cytotoxicity at low doses (22.5 micromol l(-1) and 45 micromol l(-1)) and induced terminal myogenic differentiation in RD cells (a rhabdomyosarcoma cell line) treated for 6 days. Changes in morphological features and in protein organization indicated re-entry in the pathway of muscular maturation. Moreover, GR-891 increased adhesion capability mediated by the expression of fibronectin, and did not induce overexpression of P-glycoprotein, the mdr1 gene product, implicated in multidrug resistance. New acyclonucleoside-like compounds such as GR-891 have important potential advantages over 5-fluorouracil because of their lower toxicity and their ability to induce myogenic differentiation in rhabdomyosarcoma cells. Our results suggest that this drug may be useful for differentiation therapy in this type of tumour.

Matrix remodelling in dilated cardiomyopathy entails the occurrence of oncofetal fibronectin molecular variants

OBJECTIVES

To investigate whether disturbance of the cellular homoeostasis and integrity of cardiomyocytes in dilated cardiomyopathy (DCM) is accompanied by alterations in cell-matrix relations as indicated by changes in the deposition of fibronectin (FN) isoforms.

DESIGN

Tissue from a case series of patients with DCM was investigated by immunohistochemistry with antibodies against FN (all variants, clone IST4), ED-A+ FN (clone IST9), ED-B+ FN (clone BC1), and oncofetal glycosylated FN (clone 5C10). The sites of de novo synthesis of FN were demonstrated by means of non-radioactive RNA in situ hybridisation (ISH) with biotinylated FN cDNA fragments as the probe.

SETTING

University hospital.

PATIENTS

Samples from 10 patients with clinical criteria and histological diagnosis of DCM and from 3 individuals with normal hearts.

INTERVENTIONS

Samples were obtained by right ventricular endomyocardial biopsy.

MAIN OUTCOME MEASURE

Distribution of oncofetal FN variants in DCM hearts.

RESULTS

Immunostaining of FN (IST4, all variants) showed a coarse interstitial network in normal and diseased myocardium. ED-A+ FN was deposited as fine interstitial spots in normal myocardium and in DCM samples. Immunostaining for oncofetal glycosylated FN and ED-B+ FN was not seen in normal adult myocardium, whereas myocardium from DCM patients showed focal and delicate staining in the interstitium. RNA ISH showed that these deposits resulted from local FN synthesis.

CONCLUSION

The results accord with de novo expression of oncofetal FN variants in hearts from patients with DCM. The oncofetal FN variants may serve as disease markers in myocardium affected by DCM.

Differential expression of fibronectin splice variants, oncofetal glycosylated fibronectin and laminin isoforms in nodular palmar fibromatosis

The tissue formation process in nodular palmar fibromatosis (Morbus Dupuytren) was investigated by the demonstration of fibronectin splice variants (ED-A and ED-B fibronectin), de novo glycosylated fibronectin and laminin isoforms (A, M, B1, B2, s chains) in association to the proliferative activity (Ki-67 antigen) and the occurrence of myofibroblast phenotype (alpha-smooth muscle actin, desmin). The proliferative noduli of the fibromatosis were characterized by a diffuse immunostaining for alpha-smooth muscle actin, and single cells positive for desmin and the Ki-67 antigen. In contrast to the surrounding aponeurosis as extracellular matrix, components of the whole proliferative noduli were defined: ED-A, ED-B and de novo glycosylated fibronectin, B1 and B2 laminin chain, tenascin and collagen type IV. The demonstration of the A and M laminin chain was restricted to a few cells of the proliferative noduli. S laminin could be visualized in the majority of palmar aponeurotic fibroblasts. As revealed by mRNA, in situ hybridization a de novo synthesis of fibronectin could only be detected within proliferative noduli. There is a positive correlation between the myofibroblast phenotype formation, cellular proliferation and the occurrence of ED-A and ED-B containing fibronectin, as well as de novo glycosylated fibronectin in Dupuytren's disease. The ultrastructural irregularities of myofibroblastic basal lamina and the heterogeneity of the myofibroblast phenotype are equivalent to the variability of laminin isoform immunostaining.