IL-6 stimulation of DNA replication is JAK1/2 mediated in cross-talk with hyperactivated ERK1/2 signaling

Area of Science:

• Hematology
• Oncology
• Molecular Biology

Background:

• Myeloproliferative neoplasms (MPNs) are a group of blood cancers characterized by the overproduction of myeloid cells.
• Resistance to Janus kinase (JAK) inhibitors like ruxolitinib is a significant clinical challenge in MPN management.
• Interleukin-6 (IL-6) is a key inflammatory cytokine implicated in MPN pathogenesis and progression.

Purpose of the Study:

• To investigate the mechanisms underlying ruxolitinib resistance in MPNs.
• To explore the role of IL-6 in mediating proliferation and survival signaling pathways in MPN cells.
• To elucidate the cross-talk between JAK/STAT, AKT, and ERK signaling in response to IL-6 and JAK inhibition.

Main Methods:

• Analysis of signaling pathways (STAT3, AKT, ERK1/2) in MPN granulocytes and JAK2V617F mutated human erythroleukemia (HEL) cells.
• Treatment with JAK1/2 or JAK2 inhibitors and IL-6 stimulation.
• Flow cytometry to assess cell cycle distribution (G2M and S phases) and apoptosis.

Main Results:

• JAK1/2 or JAK2 inhibition blocked IL-6-mediated STAT3 and AKT activation in polycythemia vera and HEL cells.
• Ruxolitinib significantly activated ERK1/2 signaling in essential thrombocythemia and primary myelofibrosis (PMF) granulocytes, particularly those with JAK2V617F mutation.
• Ruxolitinib reversed IL-6-induced G2M phase arrest in HEL cells, potentiated apoptosis in PMF granulocytes, and prevented IL-6-mediated S phase entry in MPN granulocytes.

Conclusions:

• Inflammatory stimulation via IL-6 induces cross-talk between proliferation-related pathways in MPNs.
• JAK1/2 inhibition by ruxolitinib can be compensated by ERK1/2 pathway activation during IL-6 stimulation, contributing to therapeutic resistance.
• Targeting this compensatory signaling may offer novel therapeutic strategies for overcoming ruxolitinib resistance in MPNs.