Identifying and targeting pathogenic PI3K/AKT/mTOR signaling in IL-6-blockade-refractory idiopathic multicentric Castleman disease.
Level 4 - case-series / case-control
Case series with translational mechanistic analysis in three patients
PubMed 31408438 · doi:10.1172/JCI126091
What was done
Tissue and blood samples from 3 patients with interleukin-6 (IL-6)-blockade refractory idiopathic multicentric Castleman disease presenting with the TAFRO clinical subtype were evaluated using cytokine profiling, quantitative serum proteomics, peripheral blood mononuclear cell flow cytometry, pathway analyses, and immunohistochemistry for phosphorylated S6. Patients were subsequently treated with the mTOR inhibitor sirolimus and assessed for clinical, proteomic, and immunophenotypic responses.
What was found
Analyses revealed increased CD8+ T cell activation, elevated VEGF-A levels, and heightened PI3K/Akt/mTOR pathway activity across the three cases. Treatment with sirolimus attenuated CD8+ T cell activation and lowered VEGF-A concentrations. All 3 patients achieved clinical benefit responses with durable, ongoing remissions lasting 66, 19, and 19 months, respectively.
Why it matters
This study identifies the PI3K/Akt/mTOR pathway as a potential therapeutic target in IL-6-refractory iMCD-TAFRO and provides preliminary clinical evidence supporting the use of sirolimus in this treatment-refractory population.
Limits
The study is limited by an extremely small sample size (n = 3), an uncontrolled case-series design, and a focus solely on the TAFRO clinical subtype, precluding definitive conclusions regarding efficacy or generalizability without prospective clinical trial data.