Myeloid cell RelA/p65 promotes lung cancer proliferation through Wnt/β-catenin signaling in murine and human tumor cells

Expression of the antimicrobial peptide cathelicidin in myeloid cells is required for lung tumor growth

Antimicrobial peptides, such as the cathelicidin LL-37/hCAP-18 and its mouse homolog cathelicidin-related antimicrobial peptide (CRAMP), are important effectors of the innate immune system with direct anti-bacterial activity. Cathelicidin is possibly involved in the regulation of tumor cell growth. The aim of this study was to characterize the role of cathelicidin expressed in non-tumorous cells in a preclinical mouse model of tumor growth. Wild-type and CRAMP-deficient animals were exposed to cigarette smoke (CS) and Lewis lung carcinoma cells were injected to initiate the growth of tumors in the lung. CS exposure significantly increased the proliferation of lung tumors in wild-type mice, but not in CRAMP-deficient mice. CS exposure induced the recruitment of myeloid cell into tumor tissue in a CRAMP-dependent manner. Mice lacking RelA/p65 specifically in myeloid cells showed impaired recruitment of CRAMP-positive cells into the lung. In vitro studies with human cells showed that LL-37/hCAP-18 in macrophages is induced by soluble factors derived from cancer cells. Taken together, these data indicate that cathelicidin expressed from myeloid cells promotes CS-induced lung tumor growth by further recruitment of inflammatory cells. The regulation of cathelicidin expression involves myeloid p65/RelA and soluble factor from tumor cells.

CDA-2, a urinary preparation, inhibits lung cancer development through the suppression of NF-kappaB activation in myeloid cell

CDA-2 (cell differentiation agent 2), a urinary preparation, has potent anti- proliferative and pro-apoptotic properties in cancer cells. However, the mechanisms of tumor inhibitory action of CDA-2 are far from clear, and especially there was no report on lung cancer. Here we demonstrate that CDA-2 and its main component phenylacetylglutamine (PG) reduce the metastatic lung tumor growth, and increases survival time after inoculation with Lewis lung carcinoma (LLC) cells in a dose-dependent manner in C57BL6 mice. Proliferative program analysis in cancer cells revealed a fundamental impact of CDA-2 and PG on proliferation and apoptosis, including Bcl-2, Bcl-XL, cIAP1, Survivin, PCNA, Ki-67 proteins and TUNEL assays. CDA-2 and PG significantly reduced NF-κB DNA-binding activity in lung cancer cells and in alveolar macrophages of tumor bearing mice and especially decreased the release of inflammatory factors including TNFα, IL-6, and KC. Furthermore, CDA-2 and PG decrease the expressions of TLR2, TLR6, and CD14, but not TLR1, TLR3, TLR4, and TLR9 in bone-marrow-derived macrophages (BMDM) of mice stimulated by LLC-conditioned medium (LLC-CM). Over-expressing TLR2 in BMDM prevented CDA-2 and PG from inhibiting NF-κB activation, as well as induction of TNFα and IL-6. TLR2:TLR6 complexes mediate the effect of NF-κB inactivation by CDA-2. In conclusion, CDA-2 potently inhibits lung tumor development by reduction of the inflammation in lung through suppression of NF-κB activation in myeloid cells, associating with modulation of TLR2 signaling.