JAK1 and cancer: Since STAT3 serves as a converging point of several oncogenic signaling pathways, including JAK1/2, EGFR, HER2, Src [40], and TrkA (current study) and STAT3 transcriptionally activates expression of many important cancer-related genes [40], it is critically important to completely inhibit STAT3 activity to effectively inhibit cancer growth and metastasis.