Published in:
01-08-2015 | Original Article – Cancer Research
Argininosuccinate synthetase (ASS) deficiency in high-grade pulmonary neuroendocrine carcinoma: an opportunity for personalized targeted therapy
Published in: Journal of Cancer Research and Clinical Oncology | Issue 8/2015
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Purpose
Cells deficient in argininosuccinate synthetase (ASS) must absorb the arginine they need for growth from circulating blood. Treatment with pegylated arginine deiminase (ADI-PEG 20) selectively eliminates arginine from the circulation and has shown some efficacy against ASS-deficient tumors including small cell lung cancer (SCLC). We sought to assess ASS expression in a cohort of high-grade pulmonary neuroendocrine carcinomas (PNEC) which include SCLC and large cell neuroendocrine carcinoma (LCNEC).
Methods
Sixty-nine PNEC (49 SCLC and 20 LCNEC) were retrieved from our pathology archives. Formalin-fixed paraffin-embedded sections of the 54 primary tumors, 15 metastases and appropriate positive and negative controls were immunostained using an ASS-specific monoclonal antibody. Positive staining in <30 % of the tumor was scored as weak; staining in ≥30 % of the tumor was scored as strong. The absence of staining in the tumor was recorded as ASS negative.
Results
58 % of the PNEC including 61.2 % of the SCLC and 50 % of the LCNEC were ASS negative. These ASS-negative tumors included 63 % of the primary and 40 % of the metastatic lesions tested.
Conclusions
More than 50 % of the high-grade PNEC tested lack immunohistochemically detectable ASS, suggesting that they are auxotrophic for arginine and potential candidates for arginine deprivation therapy. PNEC comprise about 25 % of primary lung cancers and have a 5-year overall survival of only 5–10 %, underscoring the need for new and more effective therapies. Immunostaining for ASS has potential to improve the selection of patients with PNEC for arginine deprivation therapy with ADI-PEG 20.