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Buccal epithelial cells are occasionally used as a source of supposedly non‐neoplastic DNA in patients suffering from haematological malignancies. Formerly, Kralovics et al found the JAK2 V617F mutation in DNA derived from buccal swabs in only 2.2% of patients with Philadelphia‐negative chronic myeloproliferative disorders (Ph− CMPD).1
We compared the JAK2 V617F mutational status in DNA derived from buccal swabs to that in DNA extracted from either bone marrow or peripheral blood in 35 Ph− CMPD patients, including five cases of polycythaemia vera (PV), five cases of chronic idiopathic myelofibrosis (CIMF) and 25 cases of essential thrombocythaemia (ET). Genomic DNA was isolated from buccal swabs immediately on collection and from fresh‐frozen bone marrow or peripheral blood, using Sherlock AX (A&A Biotechnology, Gdynia, Poland) and QIAamp DNA Mini Kit (Qiagen GmbH, Hilden, Germany) respectively. Allele‐specific PCR for detecting the JAK2 V617F mutation was performed in duplicate samples with 100 ng DNA, as described previously.2 PCR products were analysed by electrophoresis on 2% agarose gels containing ethidium bromide at 100 V for 1–2 h.
The mutation was detected in 26 samples derived from bone marrow or blood and in 24 of 26 (92.3%) samples derived from matching buccal swabs. In two ET cases the mutation was noted in DNA derived from haematopoietic tissue only, and was absent in buccal swabs. All nine cases negative for the mutation in blood/marrow samples showed concordant negative results in the buccal swabs. The mutation‐specific 203 bp band was occasionally weaker in DNA derived from swabs compared to DNA of a direct haematopoietic origin (fig 11).
The high rate of mutation detection in our material might have resulted from a high sensitivity of the allele‐specific PCR. Also of some potential importance was the technique of buccal swab sampling, with generous bilateral collection of the material from patients' oral mucosa. Buccal swabs are most likely contaminated with leucocytes and removal of non‐epithelial cells by mouth rinsing was suggested as a precaution in chimerism studies.3 A more intriguing hypothesis, explaining why a genetic event apparently specific for the somatic haematopoietic tissue, is detected in buccal swabs may be proposed based on recently described trans‐differentiation of haematopoietic cells into epithelial cells in allogeneic bone marrow transplant recipients.4,5
The exact origin of the mutant DNA notwithstanding, buccal swabs appear to be a surprisingly good source of material for JAK2 mutation studies, provided that a sensitive mutation detection system is used. Their collection is much less invasive and cheaper, even when compared to collection of peripheral blood. On the other hand, caution has to be exercised when DNA derived from buccal swabs is planned to be used as a source of supposedly “wild‐type” genetic material for comparison with DNA derived from blood or marrow, in the studies of mutations expected to be specific for haematopoietic tissues.
Funding: Supported by the Committee for Scientific Research, Republic of Poland, grant no 3 P05B 084 24.
Competing interests: None declared.