The expression and characterization of endoglin in uterine leiomyosarcoma

Endoglin, a Novel Biomarker and Therapeutical Target to Prevent Malignant Peripheral Nerve Sheath Tumor Growth and Metastasis

PURPOSE

Malignant peripheral nerve sheath tumors (MPNST) are highly aggressive soft-tissue sarcomas that lack effective treatments, underscoring the urgent need to uncover novel mediators of MPNST pathogenesis that may serve as potential therapeutic targets. Tumor angiogenesis is considered a critical event in MPNST transformation and progression. Here, we have investigated whether endoglin (ENG), a TGFβ coreceptor with a crucial role in angiogenesis, could be a novel therapeutic target in MPNSTs.

EXPERIMENTAL DESIGN

ENG expression was evaluated in human peripheral nerve sheath tumor tissues and plasma samples. Effects of tumor cell-specific ENG expression on gene expression, signaling pathway activation and in vivo MPNST growth and metastasis, were investigated. The efficacy of ENG targeting in monotherapy or in combination with MEK inhibition was analyzed in xenograft models.

RESULTS

ENG expression was found to be upregulated in both human MPNST tumor tissues and plasma-circulating small extracellular vesicles. We demonstrated that ENG modulates Smad1/5 and MAPK/ERK pathway activation and pro-angiogenic and pro-metastatic gene expression in MPNST cells and plays an active role in tumor growth and metastasis in vivo. Targeting with ENG-neutralizing antibodies (TRC105/M1043) decreased MPNST growth and metastasis in xenograft models by reducing tumor cell proliferation and angiogenesis. Moreover, combination of anti-ENG therapy with MEK inhibition effectively reduced tumor cell growth and angiogenesis.

CONCLUSIONS

Our data unveil a tumor-promoting function of ENG in MPNSTs and support the use of this protein as a novel biomarker and a promising therapeutic target for this disease.

CD105: tumor diagnosis, prognostic marker and future tumor therapeutic target

Cancer is one of the diseases with the highest morbidity and mortality rates worldwide, and its therapeutic options are inadequate. The endothelial glycoprotein, also known as CD105, is a type I transmembrane glycoprotein located on the surface of the cell membranes and it is one of the transforming growth factor-β (TGF-β) receptor complexes. It regulates the responses associated with binding to transforming growth factor β1 egg (Activin-A), bone morphogenetic protein 2 (BMP-2), and bone morphogenetic protein 7 (BMP-7). Additionally, it is involved in the regulation of angiogenesis. This glycoprotein is indispensable in the treatment of tumor angiogenesis, and it also plays a leading role in tumor angiogenesis therapy. Therefore, CD105 is considered to be a novel therapeutic target. In this study, we explored the significance of CD105 in the diagnosis, treatment and prognosis of various tumors, and provided evidence for the effect and mechanism of CD105 on tumors.

Evaluation of Endoglin (CD105) expression in pediatric rhabdomyosarcoma

BACKGROUND

The Intratumoral Microvessel Density (IMVD) is commonly used to quantify tumoral vascularization and is usually assessed by pan-endothelial markers, such as CD31. Endoglin (CD105) is a protein predominantly expressed in proliferating endothelium and the IMVD determined by this marker measures specifically the neovascularization. In this study, we investigated the CD105 expression in pediatric rhabdomyosarcoma and assessed the neovascularization by using the angiogenic ratio IMVD-CD105 to IMVD-CD31.

METHODS

Paraffin-embedded archival tumor specimens were selected from 65 pediatric patients affected by rhabdomyosarcoma. The expression levels of CD105, CD31 and Vascular Endothelial Growth Factor (VEGF) were investigated in 30 cases (18 embryonal and 12 alveolar) available for this study. The IMVD-CD105 to IMVD-CD31 expression ratio was correlated with clinical and pathologic features of these patients.

RESULTS

We found a specific expression of endoglin (CD105) in endothelial cells of all the rhabdomyosarcoma specimens analyzed. We observed a significant positive correlation between the IMVD individually measured by CD105 and CD31. The CD105/CD31 expression ratio was significantly higher in patients with lower survival and embryonal histology. Indeed, patients with a CD105/CD31 expression ratio < 1.3 had a significantly increased OS (88%, 95%CI, 60%-97%) compared to patients with higher values (40%, 95%CI, 12%-67%). We did not find any statistical correlation among VEGF and EFS, OS and CD105/CD31 expression ratio.

CONCLUSION

CD105 is expressed on endothelial cells of rhabdomyosarcoma and represent a useful tool to quantify neovascularization in this tumor. If confirmed by further studies, these results will indicate that CD105 is a potential target for combined therapies in rhabdomyosarcoma.

Potential Therapeutic Targets in Uterine Sarcomas

Uterine sarcomas are rare tumors accounting for 3,4% of all uterine cancers. Even after radical hysterectomy, most patients relapse or present with distant metastases. The very limited clinical benefit of adjuvant cytotoxic treatments is reflected by high mortality rates, emphasizing the need for new treatment strategies. This review summarizes rising potential targets in four distinct subtypes of uterine sarcomas: leiomyosarcoma, low-grade and high-grade endometrial stromal sarcoma, and undifferentiated uterine sarcoma. Based on clinical reports, promising approaches for uterine leiomyosarcoma patients include inhibition of VEGF and mTOR signaling, preferably in combination with other targeted or cytotoxic compounds. Currently, the only targeted therapy approved in leiomyosarcoma patients is pazopanib, a multitargeted inhibitor blocking VEGFR, PDGFR, FGFR, and c-KIT. Additionally, preclinical evidence suggests effect of the inhibition of histone deacetylases, tyrosine kinase receptors, and the mitotic checkpoint protein aurora kinase A. In low-grade endometrial stromal sarcomas, antihormonal therapies including aromatase inhibitors and progestins have proven activity. Other potential targets are PDGFR, VEGFR, and histone deacetylases. In high-grade ESS that carry the YWHAE/FAM22A/B fusion gene, the generated 14-3-3 oncoprotein is a putative target, next to c-KIT and the Wnt pathway. The observation of heterogeneity within uterine sarcoma subtypes warrants a personalized treatment approach.