Bivalent role of intra-platelet serotonin in liver regeneration and tumor recurrence in humans

Background & aims: Besides its critical role during liver regeneration, serotonin (5-HT) has been found to act as a mitogenic factor in several neoplastic entities. Accordingly, we aimed to evaluate whether intra-platelet 5-HT (IP5-HT) was associated with oncological outcome after liver resection and concomitantly evaluate its ability to serve as a therapeutic target to promote liver regeneration.

Methods: A total of 96 patients undergoing liver resection for malignant liver tumors were prospectively included. Optimized plasma and serum preparation were performed and IP5-HT levels were determined. Patients were followed up for postoperative liver dysfunction (LD), morbidity, disease free and overall survival (OS).

Results: We found increased preoperative IP5-HT levels in patients with disease recurrence at 6 and 12months (p=0.046, p=0.020, respectively). In clear contrast, patients suffering from postoperative morbidity, severe morbidity or LD had significantly reduced IP5-HT levels (p=0.011, p=0.035, p=0.003, respectively). Patients with high IP5-HT levels (>134ng/ml) suffered from an increased incidence of postoperative disease recurrence at 6 and 12months (p=0.045, p=0.006, respectively) but exhibited a reduction in morbidity, severe morbidity, and LD (p=0.006, p=0.008, p=0.005, respectively). We confirmed these results in our two largest subgroups, demonstrating that they were independent of tumor type. This bivalent effect of IP5-HT was also reflected in patients receiving selective serotonin reuptake inhibitor treatment, who displayed a reduction in disease recurrence accompanied by an increase in postoperative morbidity. Yet, both early disease recurrence and morbidity worsened OS.

Conclusion: Herein, we present first clinical evidence for IP5-HT being associated with early disease recurrence after liver resection in humans. Thus, pharmacological intervention at the level of platelets and platelet-derived 5-HT to promote liver regeneration should be considered with caution. A careful definition of indications and timing is needed to promote liver regeneration without inducing deleterious effects.

Lay summary: Preoperative intra-platelet serotonin (IP5-HT) levels seem to substantially affect patient outcomes after liver resection for liver tumors. While there is a narrow window of IP5-HT levels where liver regeneration and tumor progression is balanced, excessively high IP5-HT levels (>134ng/ml IP5-HT) lead to an increased incidence of early tumor recurrence and excessively low IP5-HT levels (<73ng/ml IP5-HT) lead to a higher rate of morbidity. Ultimately, overall survival is negatively affected by both postoperative early disease recurrence and morbidity. ClinicalTrials.gov-Identifier: NCT01700231.