Distribution and mRNA expression of insulin-like growth factor system in pulmonary lymphangioleiomyomatosis

BACKGROUND

Insulin-like growth factors (IGF-1 and IGF-2), the IGF-1 receptor (IGF-1R), and IGF-binding proteins (IGFBPs) are involved in normal pulmonary development and in the pathogenesis of smooth muscle cell tumors.

METHODS

To evaluate the role of the IGF system in lymphangioleiomyomatosis (LAM), we used immunohistochemical and in situ hybridization techniques to characterize the expression of IGF-1, IGF-2, IGF-1R, and IGFBP-2, -4, -5, and -6 in lung tissue from 18 LAM patients.

RESULTS

IGF-1, ICGF-2, IGF-1R, IGFBP-1, IGFBP-2, IGFBP-4, IGFBP-5, and IGFBP-6 were expressed by LAM cells. Reactivity and mRNA expression for IGF-2 were observed in LAM cells and resembled that found in normal smooth muscle cells during pulmonary development as well as in smooth muscle cell tumors. IGFBP-2, IGFBP-4, and IGFBP-6 were associated with spindle-shaped LAM cells, whereas IGFBP-5 was associated mainly with epithelioid LAM cells.

CONCLUSIONS

These findings suggest that the IGFBPs modulate the effects of the IGFs on LAM cells. Thus, the patterns of localization and expression of components of the IGF system in LAM strongly suggest that these agents are involved in the proliferation of LAM cells.

Lymphangioleiomyomatosis (LAM): a review of clinical and morphological features

A review is presented of the clinical and morphological manifestations of lymphangioleiomyomatosis (LAM), a systemic disorder of unknown etiology that affects women. The clinical features include dyspnea, hemoptysis, recurrent pneumothorax, chylothorax, and chylous ascites. It is characterized by: 1) proliferation of abnormal smooth muscle cells (LAM cells) in pulmonary interstitium and along the axial lymphatics of the thorax and abdomen; 2) thin-walled pulmonary cysts, and 3) a high incidence of angiomyolipomas. The pulmonary cystic lesions have a characteristic appearance on high resolution computed tomography. The most specific method for diagnosing LAM is lung biopsy to demonstrate the presence of LAM cells, either by their characteristic histological appearance or by specific immunostaining with HMB-45 antibody. LAM cells differ in several important respects from the types of smooth muscle cells normally present in lung. Their reactivity with HMB-45 antibody is localized in stage I and stage II melanosomes. LAM cells show additional evidence of incomplete melanogenesis, and the significance of these observations remains to be determined. Two types of LAM cells are recognized: 1) small, spindle-shaped cells that are centrally located in the LAM nodules and are highly immunoreactive for matrix metalloproteinase-2 (MMP-2), its activating enzyme (MT-1-MMP), and proliferating cell nuclear antigen (PCNA), and 2) large, epithelioid cells that are distributed along the periphery of the nodules and show a high degree of immunoreactivity with HMB-45 antibody and with antibodies against estrogen and progesterone receptors. Types of treatment used for LAM include oophorectomy, administration of Lupron or progesterone and in very severe cases, pulmonary transplantation (following the onset of respiratory insufficiency, not relieved by O(2)).