Constitutive activation of MET signaling impairs myogenic differentiation of rhabdomyosarcoma and promotes its development and progression

Rhabdomyosarcoma (RMS) is a soft tissue sarcoma, which may originate from impaired differentiation of mesenchymal stem cells (MSC). Expression of MET receptor is elevated in alveolar RMS subtype (ARMS) which is associated with worse prognosis, compared to embryonal RMS (ERMS). Forced differentiation of ARMS cells diminishes MET level and, as shown previously, MET silencing induces differentiation of ARMS. In ERMS cells introduction of TPR-MET oncogene leads to an uncontrolled overstimulation of the MET receptor downstream signaling pathways. In vivo, tumors formed by those cells in NOD-SCID mice display inhibited differentiation, enhanced proliferation, diminished apoptosis and increased infiltration of neutrophils. Consequently, tumors grow significantly faster and they display enhanced ability to metastasize to lungs and to vascularize due to elevated VEGF, MMP9 and miR-378 expression. In vitro, TPR-MET ERMS cells display enhanced migration, chemotaxis and invasion toward HGF and SDF-1. Introduction of TPR-MET into MSC increases survival and may induce expression of early myogenic factors depending on the genetic background, and it blocks terminal differentiation of skeletal myoblasts. To conclude, our results suggest that activation of MET signaling may cause defects in myogenic differentiation leading to rhabdomyosarcoma development and progression.

Prediction of nonSVR to therapy with pegylated interferon-alpha2a and ribavirin in chronic hepatitis C genotype 1 patients after 4, 8 and 12 weeks of treatment

In patients with chronic hepatitis C genotype 1, the current algorithm for treatment discontinuation is based on no early virological response (<2 log decline in hepatitis C virus (HCV)-RNA) at 12 weeks. It is important to determine whether prediction of nonsustained virological response (NR) before 12 weeks can be robustly obtained by statistical methods. We used longitudinal discriminant analysis (LDA) to build and cross-validate models including baseline patient characteristics and measurements of serum HCV-RNA in the first 4, 8 or 12 weeks of treatment. The performance of each model was evaluated by the partial AUC (PA) index, exploring the accuracy of prediction in the range of high negative predictive values. Models were compared by computing 95% confidence intervals for the difference in PA indices. NR was best predicted before week 12 by a single HCV-RNA measurement at week 8 taken together with gender, BMI and age (W8 model, PA index = 0.857). This model was not inferior to models that included a measurement at week 12 (PA index = 0.831). The best model obtained with LDA within the first 4 weeks, which included measurements at days 4, 8 and at week 4, was found to be inferior to the week 8 model (PA index = 0.796). These results indicate that lack of sustained viral response is best predicted after 8 weeks of treatment and that waiting until 12 weeks does not improve the prediction.

Abstract A112: Cell differentiation and downregulation of MET receptor as novel approaches for rhabdomyosarcoma treatment

Introduction: The molecular basis for loss of cell differentiation in the process of carcinogenesis is not well understood but differentiation status of the given tumor strongly influences its progression and metastatic ability and therefore the overall patient survival. Rhabdomyosarcoma (RMS) is one of most frequent soft tissue tumor occurring in children and adolescent. The precise molecular mechanism responsible for the disruption of myogenesis, characteristic for RMS tumors, is not fully understood. Activation of MET receptor has been shown to influence proliferation, survival and migration of RMS cells and MET is rapidly downregulated at the onset of myogenic differentiation. However, the influence of MET receptor on differentiation status of RMS has not been studied at all.

Objectives: We have focused on the induction of differentiation as a novel approach for RMS treatment and looked at the role of MET receptor in this process.

Materials and Methods: The expression of muscles specific genes (MyoD, Myogenin) was evaluated using RT-PCR and western blot in differentiated RMS cells and RMS cells with downregulated MET receptor. Number of apoptotic cells was studied by Annexin V binding assay. In order to study the differentiation potential of MET negative cells, RMS animal model in NOD-SCID mice was developed. We studied tumor morphology (H&E staining), maturity (desmin staining) and proliferation rate (Ki67 staining).

Results: We found that in control cells (poorly maturated RH30 cell line), the expression of MyoD (present in undifferentiated muscle cells) was high whereas during differentiation it decreased. On the other hand, Myogenin expression (present in more matured muscle cells) markedly increased at the same time. We noticed increased number of apoptotic cells in differentiation medium with 2 % of horse serum. We also obtained RMS cell lines with stable downregulation of MET receptor. The expression of differentiation related genes in MET negative cells was similar to serum differentiated RMS cells. MyoD expression was almost completely reduced in these cells. Analysis of tumor lesions formed in NOD-SCID mice showed that tumors with downregulation of MET were much more differentiated and their proliferation rate was much lower. MET negative tumors were also less metastatic in comparison to wild type controls. These data are in concordance with decreased expression of MyoD in vitro and suggest higher differentiation level of MET negative tumors in vivo.

Summary: In this study, for the first time, we have shown that differentiation of RMS cells is connected to the decrease of expression and signaling of MET receptor. These findings might have the significant clinical implication for the treatment of RMS cells because they suggest that induction of differentiation of RMS cells by e.g. blocking MET receptor might have influence on the aggressiveness/metastatic potential of these tumors.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A112.

High anti tumor activity against rhabdomyosarcoma cells and low normal cells cytotoxicity of heat shock protein 90 inhibitors, with special emphasis on 17-[2-(pyrrolidin-1-yl)ethyl]-aminno-17-demethoxygeldanamycin

Rhabdomyosarcoma is a highly metastatic tumor, mostly observed in children and adolescence. When diagnosed at early stages it is mostly curable. However, in advanced or metastatic stages the 5-years survival rate is below 20%. Thus, new treatment strategies for this tumor are needed. In this paper we showed that HSP90 inhibitors, geldanamycin and its analogs, can profoundly affect proliferation of rhabdomyosarcoma cells. We also showed that blocking of HSP90 function induces apoptosis of tumor cells and downregulates expression of anti apoptotic protein AKT. Cells exposed to geldanamycin and its analogs exhibit strong reduction of MET receptor expression and subsequent inhibition of HGF-dependent tumor cells migration and invasion. Interestingly, at concentrations sufficient to block tumor cells growth and motility, the 17AEP-GA, 17AAG and 17DMAP-GA were not toxic or only slightly toxic toward normal hematopoietic, mesenchymal and endothelial cells. This could be due to low HSP90 expression both at mRNA and protein level in these cells. Collectively, our findings suggest that blocking HSP90 action through geldanmycins could be in the future a part of new therapeutic strategies in rhabdomyosarcoma treatment.

Prevalence, risk factors and outcome of hyperlactataemia in HIV-infected patients

OBJECTIVE

We describe the prevalence, risk factors and outcome of hyperlactataemia (HL) in a cohort of 140 HIV-infected patients.

PATIENTS AND METHODS

Patients were enrolled consecutively within a 3-month period (July to September 1999) and followed until 31 October 2000. One hundred and forty HIV-infected patients had venous plasma lactate levels measured. HL was defined at baseline by two consecutive lactate levels > 2.1 mmol/L (upper limit of normal). We compared baseline demographic characteristics, immuno-virological parameters, antiretroviral therapy and outcome between patients with HL (cases) or without HL (controls). We described the clinical features of patients with HL.

RESULTS

Among 129 patients included in the analysis, HL was found in 11 patients (8.5%), all of whom were receiving nucleoside reverse transcriptase inhibitors (NRTIs). Cases were more likely than controls to receive didanosine or stavudine (82% vs. 19%, P= 2.7 x 10(-6) and 82% vs. 48%, P= 0.03, respectively). Only 4/11 cases (36%) had symptoms consistent with HL. After a median follow-up of 15 months, lactate level returned to normal in all three patients who discontinued NRTIs, but in only 2/8 patients who did not (P = 0.06). Only one case experienced lactic acidosis and died during follow-up. Mortality rate was similar in cases and controls.

CONCLUSION

HL is associated with NRTI use, in particular didanosine and stavudine, and discontinuation of NRTIs seems to be associated with rapid resolution of HL. Lactic acidosis remains rare and the long-term outcome of patients with HL does not seem to be poorer than controls.

[Dermatology in private practice in France in 2000]

OBJECTIVES

Data regarding French dermatological practice are scarce. Our objective was to identify the skin disorders most commonly diagnosed by office-based dermatologists. We also documented the severity of these skin disorders, as reflected by the repercussions on patient's everyday life, and the way physicians managed patients.

DESIGN

We carried out a one-day survey of visits to a randomly selected sample of 900 French office-based dermatologists. The randomization was stratified according to the five French different dialing area codes.

RESULTS

Office-based dermatologists saw 6411 patients with 7839 skin disorders during the survey. The daily number of visits to French dermatologists was estimated at 47 000 and the annual number between 12 and 14 millions. Office-based dermatologists mostly managed warts, acne, nevus, dermatitis, malignancies and pre-malignancies, fungal infection and psoriasis. Repercussions on patients'everyday life were assessed by physicians as important or very important in 28 p. 100 of cases. Half of the patients received topical treatment, 20.5 p. 100 a systemic drug and 40 p. 100 a minor surgical procedure (including cryotherapy).

CONCLUSION

Although dermatologists frequently see benign skin disorders such as warts or nevus, more severe diseases represent an important part of their activity.

[Incidence and management of condylomata acuminata by French general physicians]

OBJECTIVES

Condylomata acuminata (or genital warts) are sexually transmitted diseases caused by human papillomavirus. Until now, there has been no available epidemiologic data about this disease in France. We conducted a prospective study among French general practitioners (GPs) to estimate the incidence of consultations for external condylomata acuminata in general practice. We also assessed the management of patients with external condylomata acuminata by French GP's.

DESIGN

A panel of French general practitioners, members of the Sentinel network, had to fill-in prospectively a questionnaire for each patient with condylomata acuminata diagnosed between July and November 2000.

RESULTS

The annual number of consultations for external condylomata acuminata with French GP's was estimated at 23,000 (CI (95 p. 100) 21,000-25,000) including 15,000 new cases (CI (95 p. 100) 13,000-17,000). Taking into account the estimations we made at the same time in office-based private dermatologists, we estimated the annual incidence of external condylomata acuminata in France at 107/100 000 inhabitants. The management of patients with external condylomata acuminata by French GP's was in accordance with the European guidelines in 54 to 78 p. 100 of cases. French GP's mostly prescribed chemical treatment.

DISCUSSION

A proportion of cases of condylomata acuminata may have not been diagnosed. Similarly, some lesions may have been wrongly diagnosed as condylomata acuminata, but these proportions of false positive and false negative remain unknown. The incidence of external condylomata acuminata in France is similar to those estimated in others developed countries.

[Comparison of three scales to assess health risk perception]

BACKGROUND

Health risks management consists of quantitative and qualitative assessment of risks including risk perception among different samples of the population. Little work has been done to develop and validate scales to measure risk perception.

METHODS

We conducted, in December, 1999, a study among 1358 French GPs, members of the Sentinels network, in order to compare three scales: a visual analog scale, a verbal scale and a numerical scale. GPs were asked about their own perception of two risks: the Creutzfeldt-Jakob disease new variant (vMCJ) and the bug.

RESULTS

The response rate was 55%, with no difference between the three groups (p=0.85). No statistically significant difference was observed between the distributions of the visual analog scale and the numerical scale (p=0.11 for the question about the vMCJ and p=0.98 for the question about the bug). Conversely, distributions of the verbal scale were significantly different from those of the visual analog scale (p<0.0001 for both of the questions) and from those of the numerical scale (p<0.0001 for both of the questions). Separation between worried and non worried people didn't occur in the middle of the visual analog scale but at 33 millimeters from the left extremity for the question about the vMCJ and at 41 millimeters from the same extremity for the question about the bug.

CONCLUSION

We recommend the use of verbal scales to measure instantaneous perception of a given risk. Visual analog scales and numerical scales are known to be the best scales to detect minimum changes in the perception of functional signs such as pain. On this purpose, their superiority with regard to verbal scales has to be confirmed in the field of risk perception.