SMAD2 and myeloproliferative neoplasm: However, whereas induction of CCN2 gene transcription by TGF-β typically involves the canonical SMAD2/3 pathway [6], a recent study showed that noncanonical c-Jun N-terminal kinase (JNK)-dependent TGF-β signaling in mesenchymal stromal cells is responsible for the development of BM fibrosis in MPN [19].