Reduced argininosuccinate synthetase expression in refractory sarcomas: Impacts on therapeutic potential and drug resistance.

Youngji Kim,Shigehisa Kitano,Yoshiyuki Suehara,Kazuo Kaneko,Kenta Mukaihara,Ayumu Ito,Keisuke Akaike,Akira Kawai,Daisuke Kubota,Eisuke Kobayashi,Hirokazu Chuman

doi:10.18632/oncotarget.12225

Youngji Kim, Shigehisa Kitano + Show 9 more

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https://doi.org/10.18632/oncotarget.12225

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Abstract

BackgroundTreating drug-resistant sarcomas remains a major challenge. The present study aimed to identify a novel therapy for drug-resistant sarcomas based on metabolic errors involving argininosuccinate synthetase1 (ASS1).ResultsASS1 expression was reduced in Dox-resistant sarcoma cells. Immunohistochemistry and real-time PCR showed an inverse correlation between ASS1 and P-gp expressions. The inhibition of cellular proliferation with G1-arrest was shown to lead to autophagy with arginine deprivation. In addition, the combination of an autophagy inhibitor plus arginine deprivation was more effective than arginine deprivation alone. In cells with suppressed ASS1 expression, P-gp expression was upregulated as compared to that in negative controls.DiscussionThese results indicate that the reduced ASS1 expression in Dox-resistant sarcomas may contribute to drug resistance in association with the expression of P-gp. ASS1 deficiency is a potential target for novel drug therapies. The combination of arginine-deprivation therapy and an autophagy inhibitor may have anti-tumor effects in refractory sarcomas.MethodsWe assessed the expressions of ASS1 and P-glycoprotein (P-gp) in clinical specimens and cell lines of osteosarcoma (KHOS), doxorubicin (Dox)-resistant osteosarcoma (KHOSR2), epithelioid sarcomas (ES-X and VAESBJ) and alveolar soft part sarcoma (ASPS-KY). Each cell line was cultured in arginine-containing and arginine-free media. Cell growth was assessed using an XTT assay and flow cytometry. We analyzed the induction of autophagy in arginine-free medium. Moreover, we assessed the expression of P-gp after suppressing ASS1 in Dox-sensitive cells (MCF-7 and KHOS) and after transfecting ASS1 into Dox-resistant cells (ES-X, VAESBJ, ASPS-KY and KHOSR2).

Highlights

The prognosis of patients with sarcomas has improved since the introduction of chemotherapy in the 1980s [1]
argininosuccinate synthetase1 (ASS1) expression was reduced in Dox-resistant sarcoma cells
In cells with suppressed ASS1 expression, P-gp expression was upregulated as compared to that in negative controls. These results indicate that the reduced ASS1 expression in Doxresistant sarcomas may contribute to drug resistance in association with the expression of P-gp

Summary

Introduction

The prognosis of patients with sarcomas has improved since the introduction of chemotherapy in the 1980s [1]. Some bone and soft-tissue sarcomas initially have or develop resistance to currently available chemotherapeutic agents and this remains a major clinical challenge. Complete excision of the primary tumor is the only curative treatment option [6, 7], most patients already have metastatic dissemination (especially to the lungs and brain) at the time of diagnosis. In such inoperable cases, the outcomes are very poor [8]. The present study aimed to identify a novel therapy for drug-resistant sarcomas based on metabolic errors involving argininosuccinate synthetase (ASS1)

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Conclusion