Alternative splicing of Apoptosis Stimulating Protein of TP53-2 (ASPP2) results in an oncogenic isoform promoting migration and therapy resistance in soft tissue sarcoma (STS)

• Published in: BMC cancer 2022-07, Vol.22 (1), p.1-725, Article 725
• Main Authors: Tsintari, Vasileia, Walter, Bianca, Fend, Falko, Overkamp, Mathis, Rothermundt, Christian, Lopez, Charles D., Schittenhelm, Marcus M., Kampa-Schittenhelm, Kerstin M.
• Format: Article
• Language: English
• Subjects: Alternative splicing; Amino acids; Apoptosis; ASPP2κ; Binding sites; Cancer; Cancer therapies; Care and treatment; Cell culture; Chemotherapy; Complications and side effects; Experiments; Gene expression; Genetic aspects; Immunohistochemistry; Leukemia; Liposarcoma; Lymphoma; Metastases; Molecular modelling; Oncogenes; Oncology, Experimental; p53; p53 Protein; Paraffin; Patients; Prevention; Protein expression; Proteins; Rhabdomyosarcoma; Risk factors; Sarcoma; Soft tissue sarcoma; Software; Statistical analysis; Therapeutic targets; Tumor cell lines; Tumor proteins; Tumor suppressor genes; Tumors; Wound healing
• ISSN: 1471-2407; 1471-2407
• DOI: 10.1186/s12885-022-09726-7

Background Metastatic soft tissue sarcoma (STS) are a heterogeneous group of malignancies which are not curable with chemotherapy alone. Therefore, understanding the molecular mechanisms of sarcomagenesis and therapy resistance remains a critical clinical need. ASPP2 is a tumor suppressor, that functions through both p53-dependent and p53-independent mechanisms. We recently described a dominant-negative ASPP2 isoform (ASPP2?), that is overexpressed in human leukemias to promote therapy resistance. However, ASPP2? has never been studied in STS. Materials and methods Expression of ASPP2? was quantified in human rhabdomyosarcoma tumors using immunohistochemistry and qRT-PCR from formalin-fixed paraffin-embedded (FFPE) and snap-frozen tissue. To study the functional role of ASPP2? in rhabdomyosarcoma, isogenic cell lines were generated by lentiviral transduction with short RNA hairpins to silence ASPP2? expression. These engineered cell lines were used to assess the consequences of ASPP2? silencing on cellular proliferation, migration and sensitivity to damage-induced apoptosis. Statistical analyses were performed using Student's t-test and 2-way ANOVA. Results We found elevated ASPP2? mRNA in different soft tissue sarcoma cell lines, representing five different sarcoma sub-entities. We found that ASSP2? mRNA expression levels were induced in these cell lines by cell-stress. Importantly, we found that the median ASPP2? expression level was higher in human rhabdomyosarcoma in comparison to a pool of tumor-free tissue. Moreover, ASPP2? levels were elevated in patient tumor samples versus adjacent tumor-free tissue within individual patients. Using isogenic cell line models with silenced ASPP2? expression, we found that suppression of ASPP2? enhanced chemotherapy-induced apoptosis and attenuated cellular proliferation. Conclusion Detection of oncogenic ASPP2? in human sarcoma provides new insights into sarcoma tumor biology. Our data supports the notion that ASPP2? promotes sarcomagenesis and resistance to therapy. These observations provide the rationale for further evaluation of ASPP2? as an oncogenic driver as well as a prognostic tool and potential therapeutic target in STS. Keywords: Soft tissue sarcoma, Rhabdomyosarcoma, Alternative splicing, ASPP2?, p53, Oncogenes, Tumor suppressor, Apoptosis, Therapy resistance