HMGB1 concentration measurements in trauma patients: assessment of pre-analytical conditions and sample material

BACKGROUND

HMGB1 is a mediator of systemic inflammation in sepsis and trauma, and a promising biomarker in many diseases. There is currently no standard operating procedure for pre-analytical handling of HMGB1 samples, despite that pre-analytical conditions account for a substantial part of the overall error rate in laboratory testing. We hypothesized that the considerable variations in reported HMGB1 concentrations and kinetics in trauma patients could be partly explained by differences in pre-analytical conditions and choice of sample material.

METHODS

Trauma patients (n = 21) admitted to a Norwegian Level I trauma center were prospectively included. Blood was drawn in K2EDTA coated tubes and serum tubes. The effects of delayed centrifugation were evaluated in samples stored at room temperature for 15 min, 3, 6, 12, and 24 h respectively. Plasma samples subjected to long-term storage in - 80 °C and to repeated freeze/thaw cycles were compared with previously analyzed samples. HMGB1 concentrations in simultaneously acquired arterial and venous samples were also compared. HMGB1 was assessed by standard ELISA technique, additionally we investigated the suitability of western blot in both serum and plasma samples.

RESULTS

Arterial HMGB1 concentrations were consistently lower than venous concentrations in simultaneously obtained samples (arterial = 0.60 x venous; 95% CI 0.30-0.90). Concentrations in plasma and serum showed a strong linear correlation, however wide limits of agreement. Storage of blood samples at room temperature prior to centrifugation resulted in an exponential increase in plasma concentrations after ≈6 h. HMGB1 concentrations were fairly stable in centrifuged plasma samples subjected to long-term storage and freeze/thaw cycles. We were not able to detect HMGB1 in either serum or plasma from our trauma patients using western blotting.

CONCLUSIONS

Arterial and venous HMGB1 concentrations cannot be directly compared, and concentration values in plasma and serum must be compared with caution due to wide limits of agreement. Although HMGB1 levels in clinical samples from trauma patients are fairly stable, strict adherence to a pre-analytical protocol is advisable in order to protect sample integrity. Surprisingly, we were unable to detect HMGB1 utilizing standard western blot analysis.

[Expression of large tumor suppressor homolog 2 gene and its promotor methylation in oral squamous cell carcinoma]

Objective: To investigate the expression of large tumor suppressor homolog 2 (LATS2) gene and its promotor methylation in oral squamous cell carcinoma (OSCC). Methods: Reverse transcription-PCR (RT-PCR) and pyrosequencing were used to detect the mRNA and promotor methylation of LATS2 gene in 72 OSCC specimens and normal oral mucosa tissues. Western blotting was used to detect the LATS2 protein in six OSCC specimens and normal oral mucosa tissues. Results: All cases had expression of LATS2 mRNA in normal oral mucosa tissues, but the expression was down-regulated significantly, only 47% (34/72) in 72 cases of OSCC showed LATS2 mRNA expression. The expression was correlated with the degree of tumor differentiation and lymph node metastasis (P<0.05). The results of pyrosequencing show that 68% of promotor methylation (49/72) in 72 cases of OSCC. Furthermore, there was significant correlation between the mRNA and promotor methylation of LATS2 gene (χ(2)=16.980, P<0.01). All the six specimens had the low LATS2 protein expression. Conclusions: The promotor methylation of LATS2 gene may play an important role in the occurrence of OSCC.