Increased secretory leukoprotease inhibitor in patients with nonsmall celllung carcinoma

BACKGROUND. It is well known that acute pulmonary inflammation, such as tha t observed in pneumonia, elevates secretory leukoprotease inhibitor (SLPI) levels in serum. A previous report indicated that serum SLPI levels in lung carcinoma patients with concurrent pneumonia were significantly higher tha n in those in patients whose disease was unaccompanied by pneumonia or in h ealthy subjects. The authors hypothesized that serum SLPI may increase in p atients with lung carcinoma, even carcinoma occurring without pneumonia, an d that cells in lung carcinoma might produce SLPI. METHODS. Serum SLPI levels in 58 patients with primary lung carcinoma unacc ompanied by pneumonia and in 42 healthy subjects were measured by an enzyme immunoassay. Twenty-four specimens from 24 of the patients with primary lu ng carcinoma also were examined immunohistochemically using the rabbit anti human SLPI antibody. RESULTS. The results of the current study confirmed that the serum levels o f SLPI in patients with primary lung carcinoma were higher than those in he althy subjects, and further found there was no significant correlation betw een serum SLPI levels and C-reactive protein in lung carcinoma patients wit hout pneumonia. When classifying primary lung carcinoma by its histology, S LPI levels in patients with adenocarcinoma and squamous cell carcinoma were significantly higher than in those in patients with small cell lung carcin oma (SCLC). In patients with nonsmall cell lung carcinoma (NSCLC), the SLPI levels in the advanced group (International Union Against Cancer Stages II I and IV disease; n = 35) were significantly elevated compared with the non advanced group (Stages I and II disease; n = 12), and such elevated SLPI le vels were reduced in some cases by an efficient response to surgical therap y or chemotherapy. Immunohistochemical studies showed that all the NSCLC ti ssues were stained with anti-human SLPI antibody, whereas staining was not noted in any of the SCLC tissues. CONCLUSIONS. The authors believe that the findings of the current study dem onstrate that cells of NSCLC produce SLPI. Furthermore, they suggest that s erum SLPI levels in serum may be a helpful marker in patients with NSCLC un accompanied by pneumonia, and that SLPI also could be used as an immunohist ochemical marker to distinguish between NSCLC and SCLC. Cancer 2000;89:1448 -56. (C) 2000 American Cancer Society.