Mammalian target of rapamycin pathway activity in alveolar soft part sarcoma

ASPSCR1::TFE3-mediated upregulation of insulin receptor substrate 2 (IRS-2) activates PI3K/AKT signaling and promotes malignant phenotype

The ASPSCR1::TFE3 fusion gene, resulting from chromosomal translocation, is detected in alveolar soft part sarcoma (ASPS) and a subset of renal cell carcinomas (RCC). The ASPSCR1::TFE3 oncoprotein, functioning as an aberrant transcription factor, contributes to tumor development and progression by inappropriately upregulating target genes. Here, we identified insulin receptor substrate 2 (IRS-2), a cytoplasmic adaptor protein, as a novel transcriptional target of ASPSCR1::TFE3. Ectopic expression of ASPSCR1::TFE3 led to increased IRS-2 mRNA and protein levels. Chromatin immunoprecipitation and luciferase assays demonstrated that ASPSCR1::TFE3 bound to the IRS-2 promoter region and enhanced its transcription. Moreover, IRS-2 was highly expressed in the ASPSCR1::TFE3-positive RCC cell line FU-UR1, while small interfering RNA-mediated depletion of ASPSCR1::TFE3 markedly decreased IRS-2 mRNA and protein levels. Functionally, IRS-2 knockdown attenuated activation of the PI3K/AKT pathway and reduced proliferation, migration, invasion, adhesion, and clonogenicity in FU-UR1 cells. Pharmacological inhibition of IRS-2 also reduced AKT activation as well as cell viability, clonogenicity, migration, invasion, and adhesion. These findings suggest that IRS-2, regulated by ASPSCR1::TFE3, promotes tumor progression by activating PI3K/AKT signaling and enhancing the malignant phenotype.

TFE3-SLC36A1 axis promotes resistance to glucose starvation in kidney cancer cells

Higher demand for nutrients including glucose is characteristic of cancer. "Starving cancer" has been pursued to curb tumor progression. An intriguing regime is to inhibit glucose transporter GLUT1 in cancer cells. In addition, during cancer progression, cancer cells may suffer from insufficient glucose supply. Yet, cancer cells can somehow tolerate glucose starvation. Uncovering the underlying mechanisms shall shed insight into cancer progression and benefit cancer therapy. TFE3 is a transcription factor known to activate autophagic genes. Physiological TFE3 activity is regulated by phosphorylation-triggered translocation responsive to nutrient status. We recently reported TFE3 constitutively localizes to the cell nucleus and promotes cell proliferation in kidney cancer even under nutrient replete condition. It remains unclear whether and how TFE3 responds to glucose starvation. In this study, we show TFE3 promotes kidney cancer cell resistance to glucose starvation by exposing cells to physiologically relevant glucose concentration. We find glucose starvation triggers TFE3 protein stabilization through increasing its O-GlcNAcylation. Furthermore, through an unbiased functional genomic study, we identify SLC36A1, a lysosomal amino acid transporter, as a TFE3 target gene sensitive to TFE3 protein level. We find SLC36A1 is overexpressed in kidney cancer, which promotes mTOR activity and kidney cancer cell proliferation. Importantly, SLC36A1 level is induced by glucose starvation through TFE3, which enhances cellular resistance to glucose starvation. Suppressing TFE3 or SLC36A1 significantly increases cellular sensitivity to GLUT1 inhibitor in kidney cancer cells. Collectively, we uncover a functional TFE3-SLC36A1 axis that responds to glucose starvation and enhances starvation tolerance in kidney cancer.

Orbital alveolar soft part sarcoma: A report of 8 cases and review of the literature

Alveolar soft part sarcoma (ASPS) is a rare soft tissue neoplasm. The incidence of orbital involvement is the highest in ASPS arising in the head and neck region. However, limited information is available regarding its clinical characteristics. The present study presents the clinical manifestations, imaging findings, pathological features, treatment strategies and prognosis records of 8 cases of orbital ASPS over the last 15 years in a single hospital, along with a review of the literature. Included were 3 male and 5 female patients, with the median age at presentation being 9.5 years. The mean average largest tumour diameter was 3.6 cm. A total of 5 patients underwent surgical excision of the tumour, with 2 undergoing orbital exenteration and 1 undergoing partial orbital exenteration. In total, 6 patients received postoperative radiotherapy and 2 received chemotherapy. Upon follow-up, 6 patients were doing well with no evidence of recurrence or metastasis. Local recurrence developed in 2 patients, of whom 1 succumbed following withdrawal from treatment. According to the present series and the cases mentioned in the literature, orbital alveolar soft part sarcoma has characteristics distinct from those of alveolar soft part sarcoma which arises in other locations. Orbital alveolar soft part sarcoma presents itself in a younger population with a shorter course of disease, smaller tumour size, improved prognosis, a marked association with the extraocular muscles and with the Ki-67 proliferation index possibly associated with prognosis of the disease.

Treatment of Metastatic, Refractory Alveolar Soft Part Sarcoma: Case Reports and Literature Review of Treatment Options in the Era of Targeted Therapy

BACKGROUND

Alveolar soft part sarcoma is a rare soft tissue sarcoma that is characterized by a pattern of slow growth with metastases to the lung, bone, and brain that is not responsive to conventional cytotoxic chemotherapy.

OBSERVATIONS

We describe 2 patients, with a combined 19 years of treatment experience including multiple different chemotherapeutic and targeted therapy regimens, surgery, and radiotherapy. We also present a review of the literature regarding treatment options to highlight recent findings.

CONCLUSIONS

Alveolar soft part sarcoma is an indolent, but persistently progressive disease. Novel therapeutic agents hold promise in its management.

Targeted Chemotherapy in Bone and Soft-Tissue Sarcoma

Historically surgical intervention has been the mainstay of therapy for bone and soft-tissue sarcomas, augmented with adjuvant radiation for local control. Although cytotoxic chemotherapy revolutionized the treatment of many sarcomas, classic treatment regimens are fraught with side effects while outcomes have plateaued. However, since the approval of imatinib in 2002, research into targeted chemotherapy has increased exponentially. With targeted therapies comes the potential for decreased side effects and more potent, personalized treatment options. This article reviews the evolution of medical knowledge regarding sarcoma, the basic science of sarcomatogenesis, and the major targets and pathways now being studied.

Genetics of rare mesenchymal tumors: implications for targeted treatment in DFSP, ASPS, CCS, GCTB and PEComa

Soft tissue and bone sarcomas comprise a heterogeneous group of mesenchymal tumors that include roughly 130 distinct diagnostic entities. Many of them are exceptionally rare, with only few cases diagnosed worldwide each year. Development of novel targeted treatment in this group of tumors is of special importance since many sarcoma subtypes are resistant to conventional chemotherapy and the effective therapeutic options are limited. In this review we aim to discuss the molecular implications for targeted therapy in selected rare soft tissue and bone sarcoma subtypes, including dermatofibrosarcoma protuberans (DFSP), alveolar soft part sarcoma (ASPS), clear cell sarcoma (CCS), giant cell tumor of bone (GCTB) and perivascular epithelioid cell neoplasms (PEComas). This article is part of a Directed Issue entitled: Rare cancers.

Novel roles for the MiTF/TFE family of transcription factors in organelle biogenesis, nutrient sensing, and energy homeostasis

The MiTF/TFE family of basic helix-loop-helix leucine zipper transcription factors includes MITF, TFEB, TFE3, and TFEC. The involvement of some family members in the development and proliferation of specific cell types, such as mast cells, osteoclasts, and melanocytes, is well established. Notably, recent evidence suggests that the MiTF/TFE family plays a critical role in organelle biogenesis, nutrient sensing, and energy metabolism. The MiTF/TFE family is also implicated in human disease. Mutations or aberrant expression of most MiTF/TFE family members has been linked to different types of cancer. At the same time, they have recently emerged as novel and very promising targets for the treatment of neurological and lysosomal diseases. The characterization of this fascinating family of transcription factors is greatly expanding our understanding of how cells synchronize environmental signals, such as nutrient availability, with gene expression, energy production, and cellular homeostasis.