Abstract. Pulmonary sarcomatoid carcinoma (PSC) is a rare histological subtype of non-small cell lung cancer, and the available studies on the response to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) is limited. In the present study, a 73-year-old female presented with a large mass in the lower right lung, which was diagnosed as a PSC on biopsy. An amplification-refractory mutation system (ARMS) test revealed that the patient possessed the wild-type EGFR gene, and the patient subsequently underwent radiotherapy (60 Gy) and four 21-day cycles of chemoradiotherapy (1,600 mg gemcitabine, days 1 and 8; 30 mg, cisplatin, days 1-3). Following radiotherapy and chemotherapy treatment, a CT scan revealed complete remission of the mass in the lower right lung, however, metastases were identified in the paraaortic lymph node, bilateral iliac fossa and the right gluteal region. Notably, an EGFR exon 21 L858R gene mutation was identified in the mass of the right gluteal metastasis. Therefore, treatment with erlotinib was initiated. The patient continued to experience progression-free survival for six months following the initiation of erlotinib therapy. However, multiple metastases were then identified, and all lesions possessed the wild-type EGFR gene, as identified by the ARMS test. The findings suggest that erlotinib is a viable therapeutic option for the treatment of PSC patients that possess an EGFR mutation. The spatio-temporal evolution of EGFR mutational heterogeneity in PSC may result in drug-resistance, which challenges EGFR-TKI therapy and EGFR gene mutation diagnosis.

Bombesin receptor–activated protein (BRAP) was found to express in the interstitial cells of human fibrotic lungs with unknown function. Its homologous protein, encoded by BC004004 gene, was also present in mouse lung tissues. We used BC004004−/− mice which lack BRAP homologous protein expression to establish a bleomycin-induced lung fibrotic model. After bleomycin treatment, BC004004−/− mice exhibited attenuation of pulmonary injury and less pulmonary fibrosis. Fibroblasts from BC004004−/− mice proliferated at a lower rate and produced less collagen. Autophagy-related gene 5 (ATG5) was identified as a partner interacting with human BRAP. Lacking BRAP homologous protein led to enhanced autophagy activity in mouse lung tissues as well as in isolated lung fibroblasts, indicating a negative regulatory role of this protein in autophagy via interaction with ATG5. Enhanced autophagy process in fibroblasts due to lack of BRAP homologous protein might contribute to the resistance of BC004004−/− mice to pulmonary fibrosis.

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