Carcinoma of the lung in Okinawa, Japan: With special reference to squamous cell carcinoma and squamous metaplasia

In Okinawa, a subtroplcal Island In southern Japan, squamous cell Carcinoma (SCC), especially the well-differentiated form, Is prevalent, while this form is relatively rare in both the mainland and other countries (e.g. United States of America). More patlents with SCC from Okinawa, moreover, were positive for human papillomavlrus (HPV) DNA by polymerase chain reaction (PCR) (79%), and harbored HPV types 6, 16 and 18, In combination. On the other hand, less than 30% of the mainland patlents were positive for HPV DNA by PCR. Those patients who were positive all harbored only one HPV type. Furthermore, in Okinawa, there were a signiflcant number of cases with adenosquamous carcinoma, and they too were positive for HPV DNA. The SCC and the adenocarcinoma cells adjacent to the SCC component In these cases were also positive for HPV DNA, and such adenocarcinoma cells were enlarged In size with relatively wide cytoplasm. The authors postulate that HPV infects adenocarcinoma cells and changes them to enlarged cells, followed by squamous metaplasla. In this report, HPV DNA was transfected to adenocarclnoma cells (cultured cell fines) and this showed that HPV causes squamous metaplasla. In addition, aberrant expression of p53 was demonstrated In a large number of the SCC cases In Okinawa. The enlarged adenocarclnoma cells adiacent to the SCC components In adenosquamous carcinomas also showed aberrant expression of p53.The recent advances In the studies of anti-oncogenes, p53, etc. and oncogenes are outlined. It Is to be noted that the molecular mechanisms of carcinogenesis in the lung have been studied In general, classifying lung tumors Into two groups, namely, small cell carcinoma (SCLC) and non-small cell carcinoma (NSCLC). However, because human lung cancer is represented by a wide variety of histological types, molecular genetic studies according to a more detailed histological subclasslflcatlon is needed.