Somatostatin and adrenocorticotrophic hormone like immunoreactivity in small cell carcinoma of the lung

Somatostatin and the lung

Lung carcinoma is the most common cause of death in the western world and is increasing particularly among women. Despite significant developments in our understanding of the molecular biology of this disease our ability to treat the various subtypes of lung cancer has been at a relative standstill for the past decade. Novel approaches to the therapy of lung tumours are required. Recent work has evaluated the potential role of somatostatin and its analogues in the treatment of lung cancer. Experimental evidence has demonstrated that lung tumours, in particular small cell lung cancer (SCLC), may express somatostatin. The significance of this expression has not yet been evaluated. Somatostatin receptors have been demonstrated on between 50-75% of SCLC cell lines and fresh tumour samples studied to date. Using radiolabelled somatostatin analogues SCLC tumours may be detected and localised in patients through scintigraphic imaging techniques. Studies have shown that SCLC cell line clonal proliferation may be inhibited in vitro with somatostatin analogues suggesting that the somatostatin receptors are functional. In-vivo growth inhibition studies have likewise yielded encouraging results with growth inhibition of somatostatin receptor positive SCLC xenografts and receptor negative SCLC and non-small cell lung cancer cell line xenografts. These latter result suggests that somatostatin analogues may inhibit tumour growth by indirect as well as direct means. These findings have laid the ground for formal clinical trials in the future.

Neuroendocrine alterations in nude mice with a human lung carcinoma producing pro-opiomelanocortin, corticotrophin-releasing hormone and arginine vasopressin

A mucoepidermoid carcinoma of the lung (ICD classification 8430/3) resected from a patient with no clinical signs of pituitary-adrenal alterations was transplanted into 2-month-old athymic nu/nu nude mice, with the purpose of studying the effects exerted by the human tumour on the host hypothalamo-pituitary-adrenal axis. The tumour produces peptides derived from different regions of pro-opiomelanocortin (POMC: ACTH, 7.6 +/- 0.7; N-terminal POMC, 6.6 +/- 0.6; beta-LPH/endorphin, 7.3 +/- 0.7; and alpha-MSH;3.8 +/- 0.5 pmol/g wet tissue) and the neuropeptides corticotrophin-releasing hormone and arginine vasopressin (CRH: 3.6 +/- 0.4 and AVP: 1.1 +/- 0.2 pmol/g wet tissue). Immunohistochemical staining of consecutive sections of the tumour indicated that staining of tumour cells for the different peptides was not uniform and although some cells co-stained with CRH and AVP, POMC-positive cells appeared to be distinct from CRH and AVP cells. Tumour extracts were chromatographed on Sephadex G-75 and fractions monitored for POMC-derived peptides. A single peak with characteristics of alpha-MSH was detected. The ACTH, N-POMC and beta-LPH/endorphin radioimmunoassays (RIA) detected a peak at large molecular weight, eluting at the position expected for POMC. These RIA systems also revealed an ACTH(1-39) peak and another peak which probably correspond to 13 kDa ACTH, a peak eluting at the position of hN-POMC(1-48), a beta-LPH-like peak, and a smaller sized peak which may represent alpha- or gamma-endorphin. The ACTH, N-POMC and beta-LPH/endorphin contents of anterior lobe (AL) extracts, but not neutrointermediate lobe (NIL) extracts, showed a striking decrease in tumour-bearing (TB) nude mice. However, while no difference was seen in the alpha-MSH content of AL extract between TB and control (C) nude mice, it decreased in NIL extracts of TB animals. The contents of CRH and AVP in stalk-median eminence extracts of TB nude mice was significantly lower than that of C nude mice. Basal plasma corticosteroids were raised in TB nude mice at levels comparable to those in stressed C nude mice, and although adrenal weights did not vary between TB and C nude mice, morphological changes indicating hypertrophy were found in the adrenal glands of the host animals. It was concluded that the tumour dramatically alters the hypothalamo-pituitary-adrenal axis of the host, and that it may be a useful model for studying tumour-host interactions in ectopic hormone-producing tumours.

An improved method of cell recovery following bronchial brushing

Cytologic examination of bronchial brush specimens is effective in diagnosing bronchogenic carcinoma. A major problem is loss of cells and cellular detail associated with the direct smear technique (DST). A more recent method, the Saccomanno brush wash (SBW), uses a narrow-mouthed vial to scrape cells off the brush directly into fixative. We sampled 12 directly visualized airway tumors using standard brush technique. The same brush was then agitated in a SBW vial, which was centrifuged, the cell pellet being smeared over a predetermined area of a slide. Designated areas of each slide were counted and total malignant cells per slide extrapolated. DST slides had significantly fewer cells than SBW slides, and cellular detail was better with SBW in seven cases, DST in one case, and equal in four cases. SBW appears preferable for handling of bronchial brush specimens.