GRP and small cell lung carcinoma: Specifically, LDH is the key enzyme in glycolytic metabolism that stimulates the interconversion of pyruvate to lactate.[6] In addition, several investigators found that LDH levels are elevated during cell malignant transformation in various types of cancer, including SCLC.[15,16] However, few reports illuminate the prognostic value of NSE, ProGRP, and LDH in SCLC patients applying first-line platinum-based chemotherapy.