OC 59.2 - Ribosomal biogenesis inhibition facilitates megakaryocyte/platelet biased haematopoiesis

Tuesday, July 12, 2022

11:00 AM – 11:15 AM

Location: ExCel Center, ICC Capital Suite Room 1

Presentation Format: In-Person

Presenting Author(s)

Vijay Bhoopalan, MS

PhD student
John curtin school of medical research, ANU
Canberra city, Australian Capital Territory, Australia

Co-Author(s)

AK

Amandeep Kaur

Postdoctoral Research Fellow
John Curtin School of Medical Research, ANU
Canberra, Australian Capital Territory, Australia
NH

Nadine Hein

Postdoctoral Fellow
John Curtin School of Medical Research, ANU
Canberra, Australian Capital Territory, Australia
KM

Kylee Maclachlan

Postdoctoral Research Fellow
Memorial Sloan Kettering Cancer Center
New York City, New York, United States
RF

Rita Ferreira

Postdoctoral Fellow
John Curtin School of Medical Research, ANU
Canberra, Australian Capital Territory, Australia
SM

Si Ming Man

Professor
John Curtin School of Medical Research, ANU
Canberra, Australian Capital Territory, Australia
RH

Ross Hannan

Professor
John Curtin School of Medical Research, ANU
Canberra, Australian Capital Territory, Australia
KH

Kate Hannan

Associate Professor
John Curtin School of Medical Research, ANU
Canberra, Australian Capital Territory, Australia
Elizabeth E. Gardiner, PhD

Professor
Australian National University
Canberra, Australian Capital Territory, Australia

Background: Recently reported Megakaryocyte (MK)-biased haematopoietic pathways can be detected in murine models of inflammation. Thrombopoietin (TPO) regulates normal thrombopoiesis by enhancing MK maturation. What triggers and controls the MK-biased pathway remains vague. Ribosomal biogenesis inhibitor CX-5461 is a candidate anti-cancer therapeutic that has completed phase I/II clinical trials and is well-tolerated. Treatment of mice and humans with CX-5461 results in an increase in circulating platelets.

Aims: To explore mechanisms underpinning CX-5461-mediated thrombopoiesis.

Methods: C57BL/6 wildtype or TPO-receptor-deficient mice received three doses/week 35 mg/kg CX-5461 or vehicle. Blood was collected for up to 42 days and enumerated by an automated blood analyser. Flow cytometry was used to assess platelet lifespan, receptor levels and function. Bone marrow was isolated, and MK number/ploidy and haematopoietic cell compartment were quantified. Plasma cytokine and TPO levels were assessed by ELISA, and liver TPO mRNA by RT-qPCR.

Results: CX-5461-treated mice showed rapid, reversible ~1.7-fold increases in platelets at day 7, while all other blood cells remained steady (lymphocytes, neutrophils) or decreased (red cells). Glycoprotein (GP)Ibα, αIIb and GPVI showed normal levels and function. A 2.3-fold increase in reticulated platelets but normal platelet lifespan was measured. Inflammatory cytokines (IL-6, TNFα, IL-1β) were within normal ranges. A >2-fold increase in MK numbers and hyperploidy was detected together with increased Sca1+MK (**p < 0.01), MK progenitors (**p < 0.01) and HSC (****p> 0.0005). CX-5461-induced platelet production was independent of TPO, as plasma TPO and liver TPO mRNA levels did not change with treatment, and CX-5461 treatment of TPO receptor-/- mice resulted in increased platelets (5-fold, ***p < 0.0005, day 28).

Conclusion(s): CX-5461 treatment triggered a TPO- and inflammation-independent, platelet/MK-biased haematopoietic pathway. This is a new and potentially advantageous feature of an anti-cancer therapeutic which may ameliorate often observed chemotherapy-induced thrombocytopenia. The application of ribosomal biogenesis inhibitors can enhance our understanding of the mechanisms governing thrombopoiesis.