Advances in the management of alveolar soft part sarcoma

Biological and therapeutic insights from animal modeling of fusion-driven pediatric soft tissue sarcomas

Survival for children with cancer has primarily improved over the past decades due to refinements in surgery, radiation and chemotherapy. Although these general therapies are sometimes curative, the cancer often recurs, resulting in poor outcomes for patients. Fusion-driven pediatric soft tissue sarcomas are genetically defined by chromosomal translocations that create a chimeric oncogene. This distinctive, almost 'monogenic', genetic feature supports the generation of animal models to study the respective diseases in vivo. This Review focuses on a subset of fusion-driven pediatric soft tissue sarcomas that have transgenic animal tumor models, which includes fusion-positive and infantile rhabdomyosarcoma, synovial sarcoma, undifferentiated small round cell sarcoma, alveolar soft part sarcoma and clear cell sarcoma. Studies using the animal models of these sarcomas have highlighted that pediatric cancers require a specific cellular state or developmental stage to drive tumorigenesis, as the fusion oncogenes cause different outcomes depending on their lineage and timing of expression. Therefore, understanding these context-specific activities could identify targetable activities and mechanisms critical for tumorigenesis. Broadly, these cancers show dependencies on chromatin regulators to support oncogenic gene expression and co-opting of developmental pathways. Comparative analyses across lineages and tumor models will further provide biological and therapeutic insights to improve outcomes for these children.

Establishment and characterization of NCC-ASPS2-C1: a novel patient-derived cell line of alveolar soft part sarcoma

Alveolar soft part sarcoma (ASPS) is a rare mesenchymal tumor characterized by rearrangement of the ASPSCR1 and TFE3 genes and a histologically distinctive pseudoalveolar pattern. ASPS progresses slowly, but is prone to late metastasis. As ASPS is refractory to conventional chemotherapy, the only curative treatment is complete surgical resection. The prognosis of advanced and metastatic cases is poor, highlighting the need for preclinical research to develop appropriate treatment options. However, ASPS is extremely rare, accounting for < 1% of all soft tissue sarcomas, and only one patient-derived ASPS cell line is available from public cell banks worldwide for research. This study reports the establishment of a novel ASPS cell line derived from the primary tumor tissue of an ASPS patient, named NCC-ASPS2-C1. This cell line retains the ASPSCR1-TFE3 fusion gene, which is characteristic of ASPS. The characterization of this cell line revealed stable growth, spheroid formation, and invasive properties. By screening a drug library using NCC-ASPS2-C1, we identified several drugs that inhibited the proliferation of ASPS cells. In conclusion, the establishment of NCC-ASPS2-C1 provides a valuable resource for advancing ASPS research and developing novel treatments for this challenging disease.

An unusual case of primary splenic soft part alveolar sarcoma: case report and review of the literature with emphasis on the spectrum of TFE3-associated neoplasms

BACKGROUND

Alveolar soft part sarcoma is a rare tumour of soft tissues, mostly localized in muscles or deep soft tissues of the extremities. In rare occasions, this tumour develops in deep tissues of the abdomen or pelvis.

CASE PRESENTATION

In this case report, we described the case of a 46 year old man who developed a primary splenic alveolar soft part sarcoma. The tumour displayed typical morphological alveolar aspect, as well as immunohistochemical profile notably TFE3 nuclear staining. Detection of ASPSCR1 Exon 7::TFE3 Exon 6 fusion transcript in molecular biology and TFE3 rearrangement in FISH confirmed the diagnosis.

CONCLUSION

We described the first case of primary splenic alveolar soft part sarcoma, which questions once again the cell of origin of this rare tumour.

Evaluation of TRIM63 RNA in situ hybridization (RNA-ISH) as a potential biomarker for alveolar soft-part sarcoma (ASPS)

Alveolar soft-part sarcoma (ASPS) is a rare soft tissue tumor with a broad morphologic differential diagnosis. While histology and immunohistochemistry can be suggestive, diagnosis often requires exclusion of other entities followed by confirmatory molecular analysis for its characteristic ASPSCR1-TFE3 fusion. Current stain-based biomarkers (such as immunohistochemistry for cathepsin K and TFE3) show relatively high sensitivity but may lack specificity, often showing staining in multiple other entities under diagnostic consideration. Given the discovery of RNA in situ hybridization (RNA-ISH) for TRIM63 as a sensitive and specific marker of MiTF-family aberration renal cell carcinomas, we sought to evaluate its utility in the workup of ASPS. TRIM63 RNA-ISH demonstrated high levels (H-score greater than 200) of expression in 19/20 (95%) cases of ASPS (average H-score 330) and was weak or negative in cases of paraganglioma, clear cell sarcoma, rhabdomyosarcoma, malignant epithelioid hemangioendothelioma, as well as hepatocellular and adrenal cortical carcinomas. Staining was also identified in tumors with known subsets characterized by TFE3 alterations such as perivascular epithelioid cell neoplasm (PEComa, average H-score 228), while tumors known to exhibit overexpression of TFE3 protein without cytogenetic alterations, such as melanoma and granular cell tumor, generally showed less TRIM63 ISH staining (average H-scores 147 and 96, respectively). Quantitative assessment of TRIM63 staining by RNA-ISH is potentially a helpful biomarker for tumors with molecular TFE3 alterations such as ASPS.

Alveolar Soft Part Sarcoma in the Female Genital Tract: Case Series with Literature Review and SEER Database Analysis

Introduction

Alveolar soft part sarcoma (ASPS) is a rare and distinct subtype of soft tissue sarcoma. This study aims to describe the unique presentation of ASPS in the female genital tract.

Methods

Prognostic factors for cancer-specific overall survival (CSS) were evaluated using multivariate analyses.

Results

In our case series, we identified a novel TFE3-PRCC gene fusion in a 24-year-old unmarried patient with cervical ASPS who underwent fertility-sparing surgery and remained recurrence-free for 41 months. The other two patients underwent radical hysterectomy and bilateral salpingo-oophorectomy. At the time of writing, the two patients had been disease-free for 49 and 71 months, fluorescence in situ hybridization showed break-apart signals for the ASPL-TFE3 gene. Among the 55 cases with available information from the PubMed/Medline database, most presented with localized disease, and at the last follow-up, all patients were alive and 45 patients showed no evidence of disease. The 5-year CSS rate in the female genital tract cohort from SEER database was 86.2%. Multivariate analysis revealed that older age was associated with a 1.042-fold increased risk of cancer-specific mortality (HR=1.042, 95% CI 1.022-1.063, P < 0.001), involvement of soft tissue including the heart was associated with a 4.786-fold higher risk (HR=4.7868, 95% CI 1.681-13.623, P= 0.003), and regional infiltration and distant metastasis were associated with approximately 8.6-fold and 18-fold higher risk of cancer-specific mortality compared to local disease, respectively (HR=8.652, 95% CI 2.529-29.63, P = 0.001; HR=18.366, 95% CI 6.153-54.817, P< 0.001). Patients who underwent radical excision did not show reduced cancer-specific mortality compared to those who underwent local excision (HR=0.492, 95% CI 0.224-1.081, P = 0.078).

Discussion

Previously unrecognized genetic diversity exists in ASPS. Patients with ASPS in the female genital tract have the lowest likelihood of presenting with a distant disease and are associated with a more favorable survival outcome.

Advances in treatment of alveolar soft part sarcoma: an updated review

Alveolar soft part sarcoma is a rare neoplasm of uncertain histogenesis that belongs to a newly defined category of ultra-rare sarcomas. The neoplasm is characterized by a specific chromosomal translocation, der (17) t(X; 17)(p11.2;q25), that results in ASPSCR1-TFE3 gene fusion. The natural history of alveolar soft part sarcoma describes indolent behaviour with slow progression in deep soft tissues of the extremities, trunk and head/neck in adolescents and young adults. A high rate of detection of distant metastasis at presentation has been reported, and the most common metastatic sites in decreasing order of frequency are the lung, bone and brain. Complete surgical resection remains the standard treatment strategy, whereas radiotherapy is indicated for patients with inadequate surgical margins or unresectable tumours. Although alveolar soft part sarcoma is refractory to conventional doxorubicin-based chemotherapy, monotherapy or combination therapy using tyrosine kinase inhibitors and immune checkpoint inhibitors have provided antitumor activity and emerged as new treatment strategies. This article provides an overview of the current understanding of this ultra-rare sarcoma and recent advancements in treatments according to the clinical stage of alveolar soft part sarcoma.

Imaging Features of Alveolar Soft Part Sarcoma: Single Institution Experience and Literature Review

Alveolar soft part sarcoma (ASPS) is an extremely rare and aggressive soft-tissue sarcoma (STS) subtype with poor prognosis and limited response to radiation therapy and chemotherapy. Prompt recognition and referral to sarcoma centers for appropriate management are crucial for patients' survival. The purpose of this study was to report ASPS pre-treatment imaging features and to examine the existing literature on this topic. Twelve patients (7 women, 5 men-mean age 27.1 ± 10.7 years) were included from our single-center experience. Ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI) available were reviewed according to an analysis grid incorporating features from the latest research on STS. Clinical, histological, and outcome data were collected. MRI was available in 10 patients (83.3%), US in 7 patients (58.3%), and CT in 3 patients (25%). Mean longest tumor diameter was 7.6 ± 2.9 cm, and all tumors were deeply seated. Large peritumoral feeding vessels were systematically found and identified on ultrasonography (7/7), MRI (10/10), and CT (3/3). US revealed a well-defined heterogeneous hypoechoic pattern, with abundant flow signals in all patients (7/7). In all patients, MRI showed mildly high signal intensity (SI) on T1-WI and high SI on T2-WI and peritumoral edema. Moreover, flow-voids (due to arteriosus high-flow) into the peritumoral/intratumoral feeding vessels were detected in the MRI fluid-sensitive sequences of all patients. At baseline, whole-body contrast-enhanced CT revealed metastases in 8/12 (66.7%) patients. A pre-treatment longest diameter > 5 cm was significantly associated with distant metastases at diagnosis (p = 0.01). A maximum diameter > 5 cm represents a risk of metastatic disease at diagnosis (odds ratio = 45.0000 (95% CI: 1.4908-1358.3585), p = 0.0285). In the comprehensive literature review, we found 14 articles (case series or original research) focusing on ASPS imaging, with a total of 151 patients included. Merging our experience with the data from the existing literature, we conclude that the hallmark of ASPS imaging at presentation are the following characteristics: deep location, a slight hyperintense MRI SI on T1-WI and a hyperintense SI on T2-WI, numerous MRI flow voids, high internal vascularization, and large peritumoral feeding vessels.

Atezolizumab for Advanced Alveolar Soft Part Sarcoma

BACKGROUND

Alveolar soft part sarcoma (ASPS) is a rare soft-tissue sarcoma with a poor prognosis and no established therapy. Recently, encouraging responses to immune checkpoint inhibitors have been reported.

METHODS

We conducted an investigator-initiated, multicenter, single-group, phase 2 study of the anti-programmed death ligand 1 (PD-L1) agent atezolizumab in adult and pediatric patients with advanced ASPS. Atezolizumab was administered intravenously at a dose of 1200 mg (in patients ≥18 years of age) or 15 mg per kilogram of body weight with a 1200-mg cap (in patients <18 years of age) once every 21 days. Study end points included objective response, duration of response, and progression-free survival according to Response Evaluation Criteria in Solid Tumors (RECIST), version 1.1, as well as pharmacodynamic biomarkers of multistep drug action.

RESULTS

A total of 52 patients were evaluated. An objective response was observed in 19 of 52 patients (37%), with 1 complete response and 18 partial responses. The median time to response was 3.6 months (range, 2.1 to 19.1), the median duration of response was 24.7 months (range, 4.1 to 55.8), and the median progression-free survival was 20.8 months. Seven patients took a treatment break after 2 years of treatment, and their responses were maintained through the data-cutoff date. No treatment-related grade 4 or 5 adverse events were recorded. Responses were noted despite variable baseline expression of programmed death 1 and PD-L1.

CONCLUSIONS

Atezolizumab was effective at inducing sustained responses in approximately one third of patients with advanced ASPS. (Funded by the National Cancer Institute and others; ClinicalTrials.gov number, NCT03141684.).

TFE3 nuclear expression as a novel biomarker of ovarian sclerosing stromal tumors and associated with its histological morphology

Sclerosing stromal tumors of the ovary are benign and tend to occur in youthful women with lobular structures at low frequencies. Three types of cells, including luteinized cells, short spindle myoid cells, and intermediate cells, are found in the lobules which abundant in the blood vessels. Currently, immunohistochemistry is used to detect normal follicles, sclerosing stromal tumors, granulosa cell tumors, and fibromas/thecomas. Our research results showed that transcription factor enhancer 3 (TFE3) was moderate to strong positive in the theca interna layer of normal follicles. TFE3 was expressed in seven out of eight sclerosing stromal tumors, mainly in luteinized cells. It did not express in 20 granulosa cell tumors. Of the nine fibromas/thecomas, TFE3 was weakly staining in 2 cases and negative in the remaining 7 cases. The expression of TFE3 was also weak in only one microcystic stromal tumor. 8 cases of sclerosing stromal tumors were analyzed by FISH using a TFE3 separation probe, and the results were negative. In short, as a nuclear transcription protein, TFE3 specifically expressed in sclerosing stromal tumors and could serve as a new marker for the diagnosis and differential diagnosis of sclerosing stromal tumors. Moreover, we speculate that TFE3 will promotes the formation of the vascular plexus after entry into the nucleus, which can further explain why sclerosing stromal tumors are different from other ovary sex-cord stromal tumors.

Alveolar Soft Part Sarcoma of the Nasolabial Fold: A Case Report and Literature Review

Alveolar soft part sarcoma (ASPS) is a rare malignancy that is morphologically characterized by a distinctive nodular, organoid, or nested growth pattern in which the cells are separated by vascularized septa. The diagnosis is based on a combination of pathologic and immunohistochemical findings and the presence of an ASPSCR1-TFE3 gene fusion revealed by next-generation sequencing. ASPS most commonly occurs as a painless mass in the lower extremity, with likely involvement in the lungs if metastasis is present. Here we report a case of ASPS that exhibited the characteristic ASPSCR1-TFE3 gene fusion along with a reciprocal fusion of TFE3-ASPSCR1, which presented in the nasolabial fold of a 31-year-old female. An intraoral approach was utilized for complete surgical resection of the malignancy, resulting in continued remission after 11 months.

TFE3 is a Novel Biomarker of Ovarian Sclerosing Stromal Tumours

Sclerosing stromal tumours of the ovary are benign and tend to occur in young women with lobular structures at low frequencies. Three types of cells, luteinized cells, short spindle myoid cells, and intermediate cells, are found in lobules, which are rich in blood vessels. Currently, immunohistochemistry and fluorescence in situ hybridization are used to detect normal follicles, sclerosing stromal tumours, granulosa cell tumours, and theca fibromas. Our research found the expression of transcription factor enhancer 3 (TFE3) was moderately and strongly positive in the inner thecal cell layer of normal follicles. It was expressed in seven out of eight sclerosing stromal tumours, mainly in luteinized cells, but not in 20 granulosa cell tumours and 1 microcystic stromal tumour. In nine cases of theca cell tumours and theca fibromas, TFE3 was not expressed, except in two cases of weak TFE3 expression. Eight cases of sclerosing stromal tumours were analysed by FISH using a TFE3 separation probe, and the results were negative. In a word, as a nuclear transcription protein, TFE3 was specifically expressed in sclerosing stromal tumours and could serve as a new marker for the diagnosis and differential diagnosis of sclerosing stromal tumours.

Current Status and Future Directions of Immunotherapies in Soft Tissue Sarcomas

Immunotherapy in soft tissue sarcoma (STS) has experienced a surge of interest in the past decade, contributing to an expanding number of therapeutic options for this extremely heterogenous group of rare malignancies. Immune checkpoint inhibitors (CPIs) targeting the PD-1 and CTLA-4 axes have demonstrated promising responses in a select number of STS subtypes, including rarer subtypes, such as alveolar soft part sarcoma, SWI/SNF-deficient sarcomas, clear cell sarcoma, and angiosarcoma. Multiple pan-subtype sarcoma trials have facilitated the study of possible predictive biomarkers of the CPI response. It has also become apparent that certain therapies, when combined with CPIs, can enhance response rates, although the specific mechanisms of this possible synergy remain unconfirmed in STS. In addition to CPIs, several other immune targeting agents, including anti-tumour-associated macrophage and antigen-directed therapies, are now under assessment in STS with promising efficacy in some subtypes. In this article, we review the state of the art in immunotherapy in STS, highlighting the pre-clinical and clinical data available for this promising therapeutic strategy.