Macrophages Facilitate Coal Tar Pitch Extract-Induced Tumorigenic Transformation of Human Bronchial Epithelial Cells Mediated by NF-κB

Abstract

ObjectiveChronic respiratory inflammation has been associated with lung cancer. Tumor-associated macrophages (TAMs) play a critical role in the formation of inflammation microenvironment. We sought to characterize the role of TAMs in coal tar pitch extract (CTPE)-induced tumorigenic transformation of human bronchial epithelial cells and the underlying mechanisms.MethodsThe expression of TAMs-specific CD68 in lung cancer tissues and paired adjacent tissues from cancer patients was determined using immunostaining. Co-culture of human bronchial epithelial cells (BEAS-2B) and macrophage-like THP-1 cells were conducted to evaluate the promotive effect of macrophages on CTPE-induced tumorigenic transformation of BEAS-2B cells. BEAS-2B cells were first treated with 2.4 µg/mL CTPE for 72 hours. After removal of CTPE, the cells were continuously cultured either with or without THP-1 cells and passaged using trypsin-EDTA. Alterations of cell cycle, karyotype, colony formation in soft agar and tumor xenograft growth in nude mice of BEAS-2B cells at passages 10, 20 and 30, indicative of tumorigenecity, were determined, respectively. In addition, mRNA and protein levels of NF-κB in BEAS-2B cells were measured with RT-PCR and western blot, respectively. B(a)P was used as the positive control.ResultsThe over-expression of TAMs-specific CD68 around lung tumor tissues was detected and associated with lung cancer progression. The tumorigenic alterations of BEAS-2B cells including increase in cell growth rate, number of cells with aneuploidy, clonogenicity in soft agar, and tumor size in nude mice in vivo occurred at passage 10, becoming significant at passages 20 and 30 of the co-culture following CTPE removal in compared to BEAS-2B cells alone. In addition, the expression levels of NF-κB in BEAS-2B cells were positively correlated to the malignancy of BEAS-2B cells under different conditions of treatment.ConclusionThe presence of macrophages facilitated CTPE-induced tumorigenic transformation of BEAS-2B cells, which may be mediated by NF-κB.

Inflammatory stimuli promote growth and invasion of pancreatic cancer cells through NF-κB pathway dependent repression of PP2Ac

“…16 Moreover, the carcinogenesis effect of TAM has been proved to be related to activation of NF-kB pathway. 17 According to the canonical NF-kB pathway cascade, 11 the phosphorylated IkB kinase (IKK) can further phosphorylate IkB, which is the cytoplasmic inhibitor of the NF-kB complex. When phosphorylated, IkB undergoes ubiquitination and proteasome-mediated degradation rapidly, resulting in the release and nuclear translocation of the NF-kB complex.…”

Macrophages Promote Coal Tar Pitch Extract-induced Tumorigenesis of BEAS-2B Cells and Tumor Metastasis in Nude Mice Mediated by AP-1

“…In established tumors, TAMs secret factors that promote tumor growth, angiogenesis and metastatic spread of cancer cells, TAMs infiltrated in the invasive front are associated with improvement in hepatic metastasis in colon cancer (Zhou et al, 2010); and TAMs could provide a favorable microenvironment for non-small lung cancer invasion and progression (Wang et al, 2011). In our previous study, we observed that the expression levels of CD68+ TAMs were increased in adjacent lung tumor tissue from lung cancer patients and correlated with lung cancer progression and metastasis (Feng et al, 2012). In the present study, we evaluated the role of macrophages on the promotion of lung cancer progression and metastasis using a nude mice model and the mechanisms involved.…”

“…Increasing evidence shows that TAMs have tumor-promotion function. In the pre-tumor stage, inflammatory cytokines and chemokines produced by TAMs can contribute to carcinogenesis transformation (Utrera- Barillas et al, 2010;Feng et al, 2012;Techasen et al, 2012). Infiltrating TAMs could produce a proliferation inducing ligand (APRIL) by direct stimulation with Helicobacter pylori (Hp) to promote the initiation of gastric lymphoma (Munari et al, 2011).…”

“…CTPE was collected as described previously (Feng et al, 2012). Dimethyl sulfoxide (DMSO) (spectroscopically pure) was added to get the extract solution.…”

“…In previous study, we demonstrated that TAMs promoted CTP extract (CTPE)-induced tumorigenecity in vitro using co-culture system of human bronchial epithelial cells (BEAS-2B) and macrophage-like THP-1 cells (Feng et al, 2012).…”