Abstract
Background: BCR-ABL1 fusion gene is the molecular hallmark of most cases of chronic myeloid leukaemia and some cases of acute lymphoblastic leukaemia. All CML cases that have Philadelphia chromosome, t (9; 22) (q34; q11) translocation express BCR-ABL1. For both diagnosis and minimal residual disease monitoring, Real Time PCR is used to quantify BCR-ABL1 in peripheral blood. However, messenger RNA (mRNA) decay faster in blood after 3 days of sample collection thereby affects the sensitivity of BCR-ABL quantitation. Using a novel RNA preservative, Oragene RNA kit, we aimed to detect BCR-ABL gene in the saliva of known CML patients. It is known that majority of white cells in saliva are trafficked from blood. We compared BCR-ABL ratios in blood and saliva. Methods: A total of 42 paired blood and saliva samples were collected in EDTA tube and Genotek Oragene RNA kit respectively. Total RNA was extracted using RNeasy kit and reverse transcribed by random hexamer priming using murine molony reverse transcriptase. BCR-ABL1 transcript types were first detected by multiplex PCR and then quantified by a duplex Real Time PCR-TaqMan chemistry with MGB probe and black hole quencher. Results: BCR-ABL1 transcripts, e14a2 and e13a2 were detected in 27(64%) and 10 (24%) samples respectively. The median BCR-ABL1 ratio values were 14.50% (range: 0.00–75.03) and 12.01 % (0.00–76.33) in saliva and blood respectively. The median ABL1 values were 3.11×103 (range: 1.28× 101–1.02 × 104) and 4.22 × 103 (range: 1.3×101–2.11 × 105) in saliva and blood respectively. The median BCR-ABL1 transcript level were 9.38×102 (range: 7.76×101–15.98 × 103) and 10.29×104 (range: 8.3×101–23.21 × 104) in saliva and blood respectively. The BCR-ABL1 ratios in saliva and blood did not differ significantly (p value = 0.808, Mann Whitney U test). However, the ABL1 value was significantly lower in saliva than blood (p value =0.0050, Mann Whitney U test). Conclusions: BCR-ABL1 ratios in blood and saliva were comparable although ABL1 level was lower in saliva indicating reduced RNA sample quantity in saliva. Saliva samples may be suitable for diagnostic testing and disease monitoring of CML patients, since this method of sampling is non-invasive, easy to collect and cost effective. In CML, Genetic variability of the host genome and cancer cells play a crucial role in the variability of response to available therapy, therefore studies to identify these predictors for more personalised treatment could be driven by this method of sampling.