Targeting the hyperactive STAT3/5 pathway in cutaneous T-cell lymphoma with the multi-kinase nuclear transporter inhibitor IQDMA
Cutaneous T-cell lymphoma (CTCL), particularly its tumor stage mycosis fungoides (MF) subtype, presents considerable therapeutic challenges since current treatment modalities show limited efficacy. This study addresses the unmet need for novel targeted therapies that inhibit the STAT3/5 pathway, which is hyperactive in CTCL. Utilizing a murine model with intradermally grafted malignant T-cell lymphoma cells, we compared the efficacy of the multi-kinase inhibitor IQDMA with the conventional, topical psoralen + UV-A (PUVA) phototherapeutic regimen. Our data show that IQDMA reduced tumor volume by 90.7% (p = 0.0001) and was significantly more effective than PUVA, which reduced the tumor volume by only 46.2% (p = 0.0074). Results of an immunobiological analysis reveal that IQDMA treatment decreased tumor cell infiltration by 29.8% (p = 0.03) and the percentage of Ki67+ cells by 25.3% (p = 0.03), indicating a reduced tumor cell proliferation rate. Moreover, remarkable 40.0% and 45.6% reductions were observed in the total STAT5 (p = 0.047) and STAT3 (p = 0.01) levels of the infiltrating tumor cells upon IQDMA treatment. STAT5 levels are directly correlated with CD3+ tumor cell infiltration, confirming the role of the STAT3/5 pathway in the disease pathogenesis. Intriguingly, while phospho-STAT5 and total STAT5 levels directly correlated in the vehicle-treated group, a negative correlation was observed in the IQDMA-treated group, indicating IQDMA action in blocking STAT5 hyperactivation. IQDMA targets PAK kinase, a nuclear transporter for phospho-STAT5; in turn, we observed a compartmental shift of phospho-STAT5 from the nucleus to the cytoplasm. These key findings establish the properties of IQDMA as a potent targeted therapy for CTCL and offer compelling evidence for its clinical evaluation.