LOSS OF ALPHA-6 AND BETA-4 INTEGRIN SUBUNITS COINCIDES WITH LOSS OF BASEMENT-MEMBRANE COMPONENTS IN ORAL SQUAMOUS-CELL CARCINOMAS

In oral squamous cell carcinomas, focal or extensive loss of basement membrane components and of integrins has been reported. The purpose of this study was to investigate whether those regions of the tumour-con nective tissue interface which lack laminin and type IV collagen coinc ide with areas of loss of the alpha6 and beta4 integrin subunits on ba sal keratinocytes. Out of a total of 15 poor and moderately or well di fferentiated squamous cell carcinomas, all showed some loss or fragmen tation of basement membrane proteins and in 12 the loss was coincident with loss of alpha6 and/or beta4. In three cases, there was loss of b asal integrin expression in areas where the basement membrane remained intact. These results provide further evidence that loss of integrins may play an important role in tumour progression and prompt us to spe culate about the sequence of events leading to tumour invasion.