A review of soft-tissue sarcomas: translation of biological advances into treatment measures

Abstract

Soft-tissue sarcomas are rare malignant tumors arising from connective tissues and have an overall incidence of about five per 100,000 per year. While this diverse family of malignancies comprises over 100 histological subtypes and many molecular aberrations are prevalent within specific sarcomas, very few are therapeutically targeted. Instead of utilizing molecular signatures, first-line sarcoma treatment options are still limited to traditional surgery and chemotherapy, and many of the latter remain largely ineffective and are plagued by disease resistance. Currently, the mechanism of sarcoma oncogenesis remains largely unknown, thus necessitating a better understanding of pathogenesis. Although substantial progress has not occurred with molecularly targeted therapies over the past 30 years, increased knowledge about sarcoma biology could lead to new and more effective treatment strategies to move the field forward. Here, we discuss biological advances in the core molecular determinants in some of the most common soft-tissue sarcomas - liposarcoma, angiosarcoma, leiomyosarcoma, rhabdomyosarcoma, Ewing's sarcoma, and synovial sarcoma - with an emphasis on emerging genomic and molecular pathway targets and immunotherapeutic treatment strategies to combat this confounding disease.

Keywords: genomics; immunotherapy; molecular pathways; sarcoma.

Figure 1

Genomic changes in soft-tissue sarcoma. Notes: Liposarcomas consist of four subtypes: well-differentiated liposarcoma (WDLS), dedifferentiated liposarcoma, myxoid liposarcoma (MLS), and pleomorphic liposarcoma (PLS). A common characteristic of WDLS, DDLS, and PLS is amplifications in HMGA2, MDM2, and CDK4. PLS bears additional CCND1 amplifications. MLS, on the other hand, harbors a fusion of TLS/FUS–CHOP, which is responsible for pathogenesis. Angiosarcomas are diverse malignancies and bear aberrations in MYC, VEGF/VEGFR, PTPRB, and PLCG1. Leiomyosarcomas have frequent X-chromosome (Chr) gains, constitutively activated Akt and losses in Chr 10, which bears the PTEN gene. The two latter aberrations lead to mTOR activation via TSC2 and are instrumental in disease pathology. Rhabdomyosarcoma can be subtyped into alveolar rhabdomyosarcoma (ARMS) and embryonic rhabdomyosarcoma (ERMS). The former is associated with PAX3/7–FOXO1 fusions and cause Hippo-pathway dysregulation accompanied by bypass of cellular senescence, and the latter is distinguished by losses in Chr 11, along with gene mutations in the Ras pathway. Other pathways involved include Hedgehog, PI3K, and p53. Ewing’s sarcoma is characterized by EWS–ETS gene fusion, and this potent transcription factor induces genes associated with proliferation, apoptosis inhibition, and metabolic changes to favor biosynthesis and cell division. Synovial sarcoma (SS) is associated with SYT–SSX fusions: SYT–SSX2 for monophasic SS and SYT–SSX1/2 for biphasic SS. Arrows indicate gene transcription.