High-affinity monomeric 67-kD laminin receptors and prognosis in pancreatic endocrine tumours.

Cell-surface high-affinity monomeric 67-kD laminin receptors have been proposed to promote the invasion and metastasis of a variety of tumours, but there are, as yet, no data regarding the expression of these molecules in pancreatic endocrine tumours (PETs). The prognosis of these very rare tumours is problematic and the only irrefutable evidence of their malignancy still continues to be the occurrence of local invasion and metastases. In this retrospective investigation, 34 functioning and 48 non-functioning sporadic PETs were evaluated for the expression of the MLuC5 monoclonal antibody, which specifically recognizes the 67-kD laminin receptors. Laminin receptors were found in 42/82 cases (51 per cent) and their expression was associated with metastatic disease (P < 0.001), high proliferative activity expressed by a Ki-67 index above 5.0 per cent (P < 0.001), absence of progesterone receptors (P = 0.013), immunoreactivity for hormones other than insulin (P < 0.001), a tumour diameter more than 3.0 cm (P = 0.001), and a fatal clinical outcome (P < 0.001). Laminin receptors were also expressed by most metastatic foci and all intravascular emboli of tumour cells. Positivity for laminin receptors was associated with shorter survival in functioning (P = 0.026) and non-functioning (P = 0.042) tumours, as well as in the whole series of pancreatic endocrine tumours (P < 0.001). On multivariate analysis, laminin receptor expression was not an independent prognostic factor, while a Ki-67 index above 5.0 per cent was the most powerful predictor of survival. However, the association of laminin receptor expression and Ki-67 index could identify a group of malignant PETs with low proliferative activity characterized by an intermediate prognosis. In conclusion, these data suggest that monomeric laminin receptors may play a role in the invasion and metastasis of PETs and that their expression may be an additional prognostic factor, along with proliferative activity.