Oral cancer among Khat users: finding evidence from DNA analysis of nine cancer-related gene mutations

Abstract

Background: Khat leaves contain the alkaloid cathinone. Research shows that khat might provoke toxicity, mutagenicity, as well as carcinogenicity.

Methods: Two groups were identified as khat abusers and were categorized by abuse time and diagnosis of oral squamous cell carcinoma (OSCC). Here, 41 participants from Group 2 were short-term khat users, and 42 participants were long-term khat users. The control group included 30 healthy individuals. The coding exons included nine cancer-related genes and were analysed. The histopathological research was conducted with H&E staining along with the TP53 protein expression by implementing immunohistochemical analyses.

Results: Here, 41 short-term khat users carried seven somatic mutations in four out of nine cancer-related genes: 29/41(70.73%) ARID1A, 24/41(58.53%) MLH1, 34/41(82.92%) PIK3CA and 36/41(87.80%) TP53. The 42 long-term khat users incorporated nine somatic mutations in five out of nin ecancer-related genes: 40/42(95.23%) ARID1A, 36/42(85.71%) ARID2, 29/42(69.04%) PIK3CA, 27/42(64.28%) MLH1, and 35/42(83.33%) TP53. Every khat user had somatic mutations related to OSCC affecting the gingiva and the lower lip. TP53 protein expression was confirmed in all immunohistochemical oral tests. Carcinoma was also positive in the histopathological analysis.

Conclusions: Khat is a mutagenic and carcinogenic plant that provoked OSCC among short-term khat users (<15 years of use) and long-term users (>15 years of use).

Keywords: Cancer-related gene; DNA analysis; Khat users; Mutations; Oral squamous cell carcinomas.

Fig. 1

The incidence of genetic mutations for the two groups including short- and long-term khat users diagnosed with OSCC

Fig. 2

Images of a 70-year-old patient with khat chewing experience since the age of 33 (a long-term khat abuser diagnosed with OSCC on the lower lip) shows exophytic lesions (initiated two months ago). The clinical evaluation revealed the following: red-white exophytic lesion accompanied by dark discoloration, lack of sensation during palpation, history of fever, and no lymph nodes seen. Biopsy analysis revealed verrucous carcinoma on the lower lip

Fig. 3

Images of micro-histopathology for H&E samples (with stain) (scale bar: 100 μm). SCC of the oral cavity areas (namely gingival and lower lip) indicates of dissymmetry among squamous cells; black circles are vascular invasion with abnormally sized cells with eminent red nucleoli (showed as yellow circles), pleomorphic big cells (related to yellow arrows), atypical mitotic effects, and some minor nucleoli. Panel a is gingival-related SCC, b is lower lip SCC related to the group of short-term khat users, c is gingival-related SCC, and d is lower lip SCC from the group of long-term khat users

Fig. 4

Photomicrographs of immune-stained areas applying TP53 antibody under a specific scale (100 μm). Immunohistochemical slides focused on staining with TP53 antibody. Samples showed a positive status for TP53 proteins among all khat users from the two groups. SCC of the oral cavity areas (gingival sites) was presented as follows: a gingival site SCC among short-term khat users; b gingival site SCC among long-term khat users