16Within tissues, cells secrete protein signals that are subsequently interpreted by 17 neighboring cells via intracellular signaling networks to coordinate a cellular response. 18 However, the oncogenic process of mutation and selection can rewire these signaling 19 networks to confer a fitness advantage to malignant cells. For instance, the melanoma 20 cell model (B16F0) creates a cytokine sink for Interleukin-12 (IL-12) to deprive neigh-21 boring cells of this important extracellular signal for sustaining anti-tumor immunity. 22 Alternatively, oncogenesis may also rewire intracellular signaling networks. To test this 23 concept, we asked whether IL-12 provides an intrinsic advantage to B16F0 melanoma 24 cells. Functionally, stimulation with IL-12 promoted the survival of B16F0 cells that 25 were challenged with a cytotoxic agent but had no rescue effect on normal Melan-A 26 melanocytes. We also explored a mechanistic basis for the functional results by sur-27 veying the phosphorylation intracellular proteins involved in canonical IL-12 signaling, 28 STAT4, and cell survival, Akt. In contrast to T cells that exhibited a canonical response § Corresponding author to IL-12 by phosphorylating STAT4, IL-12 stimulation of B16F0 cells phosphorylated 30 both STAT4 and Akt. Collectively, the data suggests that B16F0 cells have shifted 31 the intracellular response to IL-12 from engaging immune surveillance to favoring cell 32 survival. In short, identifying how signaling networks are rewired can guide therapeutic 33 strategies to restore effective immunosurveillance. 34 35 36Responses of the different cell types within tissues, such as T cells and Langerhans cells 38 within the epidermal layer of skin, are coordinated by the extracellular release of protein 39 signals. One such extracellular signal is the cytokine Interleukin-12 (IL-12) [1]. IL-12 is a 40 heterodimer comprised of a p35 and p40 subunit that is produced by antigen presenting cells, 41 like Langerhans and Dendritic cells, to boost natural killer (NK) and cytotoxic T lymphocyte 42 (CTL) activity and to polarize T helper cells towards a type 1 phenotype [2]. Activating 43 NK, CTLs and type 1 T helper cells play important roles in controlling viral infections 44 and defending against malignancy. Towards this aim, local delivery of IL-12 to the tumor 45 microenvironment has been shown to promote tumor regression in both mouse models and 46 human melanoma [3][4][5][6][7][8][9].
47Inside the cell, these extracellular signals are processed through a series of protein-protein 48 interactions that transmit this information from the cell membrane to the nucleus to orches-49 trate a cellular response. In the case of IL-12, these extracellular signals are transduced by 50 the canonical Janus-Kinase (JAK)-Signal Transducer and Activator of Transcription (STAT) 51 signaling pathway [10]. The IL-12 receptor, composed of a β1 (IL12RB1) and β2 (IL12RB2) 52 subunit, lacks intrinsic enzymatic activity and forms a complex with two JAKs, JAK2 and 53 TYK2. Autoph...