Tumor associated macrophages (TAMs) are a major type of inflammatory cell in a tumor microenvironment. Previous evidence has suggested that TAMs promote tumorigenesis, growth, invasion and metastasis, thereby affecting tumor metabolism. The mechanisms through which they affect the invasion and metastasis of lung cancer cells remain unclear. The present study investigated the effects and molecular mechanisms of TAMs on the proliferation, invasion and migration of lung adenocarcinoma A549 cells. Human mononuclear leukemia THP-1 cells were induced into TAMs. The morphological changes that occurred during the induction of the THP-1 cells were examined with a light microscope. Successful TAM formation was confirmed via flow cytometry. Proliferation, invasion and migration of the lung adenocarcinoma A549 cells were detected by EDU proliferation, scratch wound and Transwell invasion and migration assays, respectively. The expression levels of key proteins involved in the PI3K/AKT signaling pathway were detected by western blot analysis. It was identified that treatment with interleukin (IL)-4, IL-13 and Phorbol-12-myristate-13-acetate successfully induced THP-1 to form TAMs. The indirect coculture model of TAMs was established by Transwell chamber detection, and the proliferation, invasion and migration ability of lung adenocarcinoma A549 cells were enhanced. Western blot analysis indicated that the expression levels of phosphorylated (p)-PI3K and p-AKT proteins were significantly upregulated in the TAMs coculture group compared with that of the blank control group. In summary, the present study demonstrated that TAMs may promote the proliferation, invasion and migration of lung adenocarcinoma A549 cells in vitro , perhaps through the activation of the PI3K/AKT signaling pathway.

The tumor stromal microenvironment is an integral part of the occurrence and development of tumor. Cancer-associated fibroblasts (CAFs) are a key component of most tumor stromal microenvironments. The present study aimed to investigate the use of CAFs-targeted immunotherapy to fibroblast activation protein-α (FAP-α) expressed in CAFs. Recombinant adenoviral vectors containing the mouse FAP-α cDNA (rAd-FAP-α) were constructed. C57BL/6 mice were immunized with rAd-FAP-α infected dendritic cells (DCs) against FAP-α, which is overexpress in CAFs. The results demonstrated that mice vaccinated with rAd-FAP-α DCs gave rise to potent FAP-α-specific cytotoxic T lymphocytes capable of lysing Lewis lung cancer (LLC) CAFs. Furthermore, mice vaccinated with rAd-FAP-α-transduced DCs induced an effective therapeutic or protective antitumor immunity to LLC in a subcutaneous model, and prolonged overall survival time compared with mice vaccinated with the control recombinant adenovirus-transduced DCs (rAd-c DCs) or DCs alone. The results of the present study suggested that FAP-α, which is preferentially expressed in CAFs, may be considered as a potential target for killing or destroying CAFs within the tumor stromal microenvironment, and may be exploited to develop immunogenic tumor vaccines.

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