Trial Information

Betel quid chewing has been shown to have intimate correlation with oral cancer. In Taiwan,
the incidence of oral cancer is the fourth most common malignancy in male and in fact, 90%
of which has been linked to betel quid chewing. The predisposing factors in oral cancers
between the western countries and India, Southeast Asia including Taiwan are different. The
factor is smoking in the former countries and betel quid chewing is the most important one
in the latter groups. The genetic aberrations of oral cancers are different too between the
western countries and India, Southeast Asia including Taiwan. The percentage of RAS
mutations of oral cancers in the western countries is around 5%, and 35% in the India. In
Taiwan, the RAS mutation rate revealed with immunohistochemical staining is 92%, comparing
with those in western countries (62%), Japan (55-65%) and vice versa in the p53 mutations.
The percentage of p53 mutations of oral cancers in the western countries is around 50%, and
16% in the India, Southeast Asia and Taiwan. It is generally believed that betel nut itself,
arecoline and arecaidine, the major betel alkaloids, account for the etiological factors in
the pathogenesis of oral cancer while betel quid supplements, unlike the former two main
components, were reported to have little relevancy to oral cancer. Despite the fact that the
cytotoxic and genotoxic effects of betel nut extract and arecoline, arecaidine have been
extensively documented, and that some well-studied oncogenes or tumor suppressor genes have
been implicated in betel quid-related oral cancer, the molecular mechanisms, addressed in a
broader view, by which betel nut ingredients lead to oral tumorigenesis are not fully
understood. Our preliminary results, by virtue of different genome-wide screening approaches
to explore cellular functions of protein kinases in this context, identified several
candidates that showed differential expression upon treatment of BQ on primary cultures from
human oral mucosa. Of the candidates isolated, microtubule-associated protein 2 (MAP2), a
neuron-specific cytoskeletal protein that is thought to predominantly express in rat brain
cells, was found up-regulated at RNA level by RT-PCR in primary cultures. Our expanded
immunohistochemical results of normal mucosa, leukoplakia and oral squamous cell carcinoma
(OSCC) suggest that expression of the MAP2 significantly correlates with progression of
BQ-induced OSCC (P = 0.0046), since the percentage of MAP2 positive staining is as much
fourfold in BQ-exposed OSCC (41.2%) as in BQ-free OSCC (10.5%), whereas normal mucosa and
leukoplakia show much less immunoreactivity as a whole. Furthermore, the MAP2 is shown to
be preferentially expressed in histopathologically less differentiated OSCC (P = 0.014).
Finally, we show that the MAP2 is highly expressed in the majority of invasive OSCC (67%).
Consequently, this finding, in conjunction with the previous one, raise a possibility that
overexpression of the MAP2 may play a critical role in the development of highly malignant
OSCC characteristic of invasive and/or metastatic. Here we study the issue by establishing
an in vitro system where extracts from the whole betel quid sandwiches are used to treat
head and neck cancer cell lines and primary oral epithelial cells and subsequently, the
effects of such treatments will be evaluated in terms of cell migration, Western blotting.
Eight head and neck cancer cell lines and normal oral mucosae from 8 patients undergoing
oral surgery will be collected. Extracts from the whole betel quid sandwiches with the
concentration of 1.5 mg/ml will be added to the cell lines and primary oral epithelial cells
for 1,3 and 5 days, respectively. Migration assay and detection of MAP2 expression will be
performed to elucidate the relationship of MAP2 and cell migration.