p38 MAPK signaling has been implicated in the regulation of processes leading to cancer development and progression. Chronic inflammation is a known risk factor for tumorigenesis, yet the precise mechanism of this association remains largely unknown. The related p38αMAPK (MAPK14) proteins p38γ (MAPK12) and p38δ (MAPK13) were recently shown to modulate the immune response, although their role in tumorigenesis remains controversial and their function in inflammation-associated cancer has not been studied. We analyzed the role of p38γ and p38δ in colon cancer associated to colitis using the azoxymethane/dextran sodium sulphate (AOM/DSS) colitis-associated colon cancer model in wild-type (WT), p38γ-, p38δ-, and p38γ/δ-deficient (p38γ/δ−/−) mice. We found that p38γ/δ deficiency significantly decreased tumor formation, in parallel with a decrease in proinflammatory cytokine and chemokine production. Analysis of leukocyte populations in p38γ/δ−/− mouse colon showed less macrophage and neutrophil recruitment than in WT mice. Furthermore, WT chimeric mice with transplanted p38γ/δ−/− bone marrow had less tumors than WT mice transplanted with WT bone marrow, whereas tumor number was significantly increased in p38γ/δ−/− chimeric mice with WT bone marrow compared with p38γ/δ−/− mice transplanted with p38γ/δ−/− bone marrow. Together, our results establish that p38γ and p38δ are central to colitis-associated colon cancer formation through regulation of hematopoietic cell response to injury, and validate p38γ and p38δ as potential targets for cancer therapy. Cancer Res; 74(21); 1–11. ©2014 AACR.

p38 mitogen-activated protein kinase (MAPK) signalling has been implicated in the regulation of processes leading to cancer development and progression. Chronic inflammation is a known risk factor for tumourigenesis, yet the precise mechanism of this association remains largely unknown. The related p38αMAPK (MAPK14) proteins p38γ (MAPK12) and p38δ (MAPK13) were recently shown to modulate the immune response, although their role in tumourigenesis remains controversial and their function in inflammation-associated cancer has not been studied. We analysed the role of p38γ and p38δ in colon cancer associated to colitis, using the azoxymethane/dextran sodium sulphate colitis-associated colon cancer model in wild type (WT), p38γ-, p38δ- and p38γ/δ-deficient (p38γ/δ-/-) mice. We found that p38γ/δ deficiency significantly decreased tumour formation, in parallel with a decrease in proinflammatory cytokine and chemokine production. Analysis of leukocyte populations in p38γ/δ-/- mouse colon showed less macrophage and neutrophil recruitment than in WT mice. Furthermore, WT chimaeric mice with transplanted p38γ/δ-/- bone marrow (BM) had less tumours than WT mice transplanted with WT BM, whereas tumour number was significantly increased in p38γ/δ-/- chimaeric mice with WT BM compared to p38γ/δ-/- mice transplanted with p38γ/δ-/- BM. Together, our results establish that p38γ and p38δ are central to colitis-associated colon cancer formation through regulation of haematopoietic cell response to injury, and validate p38γ and p38δ as potential targets for cancer therapy.

Cancer evolution is a process that is still poorly understood because of the lack of versatile in vivo longitudinal studies. By generating murine non–small cell lung cancer (NSCLC) orthoallobanks and paired primary cell lines, we provide a detailed description of an in vivo, time-dependent cancer malignization process. We identify the acquisition of metastatic dissemination potential, the selection of co-driver mutations, and the appearance of naturally occurring intratumor heterogeneity, thus recapitulating the stochastic nature of human cancer development. This approach combines the robustness of genetically engineered cancer models with the flexibility of allograft methodology. We have applied this tool for the preclinical evaluation of therapeutic approaches. This system can be implemented to improve the design of future treatments for patients with NSCLC. Cancer Res; 74(21); 1–11. ©2014 AACR.

Cancer evolution is a process that is still poorly understood due to the lack of versatile in vivo longitudinal studies. By generating murine Non-Small Cell Lung Cancer (NSCLC) orthoallobanks and paired primary cell lines, we provide a detailed description of an in vivo, time-dependent cancer malignization process. We identify the acquisition of metastatic dissemination potential, the selection of co-driver mutations and the appearance of naturally occurring intra-tumor heterogeneity, thus recapitulating the stochastic nature of human cancer development. This approach combines the robustness of genetically engineered cancer models with the flexibility of allograft methodology. We have applied this tool for the pre-clinical evaluation of therapeutic approaches. This system can be implemented to improve the design of future treatments for NSCLC patients.

Detection of orthotopic xenograft tumors is difficult due to poor spatial resolution and reduced image fidelity with traditional optical imaging modalities. In particular, light scattering and attenuation in tissue at depths beyond subcutaneous implantation hinder adequate visualization. We evaluate the use of multispectral optoacoustic tomography (MSOT) to detect upregulated epidermal growth factor (EGF) receptor in orthotopic pancreatic xenografts using a near-infrared EGF-conjugated CF-750 fluorescent probe. MSOT is based on the photoacoustic effect and thus not limited by photon scattering, resulting in high-resolution tomographic images. Pancreatic tumor-bearing mice with luciferase-transduced S2VP10L tumors were intravenously injected with EGF-750 probe before MSOT imaging. We characterized probe specificity and bioactivity via immunoblotting, immunocytochemistry, and flow cytometric analysis. In vitro data along with optical bioluminescence/fluorescence imaging were used to validate acquired MSOT in vivo images of probe biodistribution. Indocyanine green dye was used as a nonspecific control to define specificity of EGF-probe accumulation. Maximum accumulation occurred at 6 hours postinjection, demonstrating specific intratumoral probe uptake and minimal liver and kidney off-target accumulation. Optical bioluminescence and fluorescence imaging confirmed tumor-specific probe accumulation consistent with MSOT images. These studies demonstrate the utility of MSOT to obtain volumetric images of ligand probe biodistribution in vivo to detect orthotopic pancreatic tumor lesions through active targeting of the EGF receptor. Cancer Res; 74(21); 1–9. ©2014 AACR.