Credit:Oct4 promotes M2 macrophage polarization through upregulation of macrophage colony-stimulating factor in lung cancer

M2 macrophage polarization is associated with Oct4 expression in lung cancer. a and b Flow cytometric analysis of M1 and M2 macrophages differentiated from PMA-stimulated THP-1 cells cocultured with the conditioned medium obtained from A549-Oct4 or A549-vector cells. Cells were then stained with PE-conjugated mouse anti-human CD86 or CD206 antibody, followed by stained with FITC-conjugated mouse anti-human CD68 antibody before flow cytometric analysis. Cells were first gated to exclude debris and dead cells (FSC vs. SSC), and then gated to exclude cell doublets (FL2-A vs. FL2-H). Within the CD68 cells, differential expression of the M1 macrophage marker CD86 and M2 macrophage marker CD206 is based on CD86hi and CD206hi expression, respectively. Representative dot plots (upper) and histograms (middle), as well as percentages of M1 and M2 macrophages (lower) are shown. c Percentage of M2 macrophages differentiated from PMA-stimulated THP-1 cells cocultured with the conditioned medium obtained from Oct4 knockdown (shOct4) or control (shLuc) A549 cells. d and e Oct4 expression (D) and M-CSF production (E) in various human lung cancer cells detected by immunoblot analysis and ELISA, respectively. Expression of β-actin served as the loading control. f Positive correlation of Oct4 and M-CSF levels detected in D and E, as determined by Pearson’s correlation coefficient. All data shown represent means ± SEM (n = 3 to 4)+.

Tumor-associated macrophages (TAMs) play a crucial role in tumor progression. TAMs can be classified into two main types based on their function and phenotype: M1 macrophages and M2 macrophages. M1 macrophages possess anti-tumor properties, while M2 macrophages support tumor growth and metastasis. Oct4, a key transcription factor, is typically expressed in embryonic stem cells, where it maintains pluripotency and self-renewal capabilities. However, studies have shown that high Oct4 expression is closely related to tumor invasiveness, metastasis, and drug resistance. Macrophage colony-stimulating factor (M-CSF), an important cytokine, promotes the differentiation of monocytes into macrophages and plays a crucial role in macrophage polarization. Specifically, M-CSF can promote the polarization of M2 macrophages, thereby supporting tumor growth and metastasis. Lu et al. explored the mechanism by which Oct4 upregulates M-CSF expression in lung cancer cells to promote the polarization of M2 TAMs through a series of in vivo and in vitro experiments.

This study utilized A549 lung cancer cell lines overexpressing Oct4 to investigate the effects of the conditioned medium secreted by these cells on the differentiation of monocytes into M2 tumor-associated macrophages (TAMs) through co-culture techniques. The inflammatory factors in the conditioned medium from Oct4-overexpressing A549 cells were detected using a human inflammation antibody array. Additionally, syngeneic mouse lung tumor models and clinical samples of non-small cell lung cancer (NSCLC) were employed to validate the association between Oct4, M-CSF, and M2 TAMs.

The study found that the expression of macrophage colony-stimulating factor (M-CSF) was significantly increased in A549 cells overexpressing Oct4, facilitating the generation of more M2 macrophages and enhancing the tumor's migratory capacity. Specifically, data showed that the level of M-CSF in A549-Oct4 cells was 1.36 times higher compared to control cells, while monocyte chemoattractant protein-1 (MCP-1) and interleukin-6 (IL-6) levels were increased by 1.29 times and 1.27 times, respectively. Reporter gene assays demonstrated that Oct4 could enhance the activity of the M-CSF promoter. Deletion analysis of the M-CSF promoter region indicated that deletions within the -1063 to -903 bp and -577 to -487 bp regions significantly reduced promoter responsiveness, suggesting that the Oct4 response elements (OREs) within these regions are crucial for Oct4-induced transcriptional activation. In non-small cell lung cancer (NSCLC) patient samples, high expression levels of Oct4, M-CSF, and M2 TAMs were associated with the poorest recurrence-free survival rates. These findings further indicate that Oct4 promotes the polarization of M2 TAMs by upregulating M-CSF, thereby promoting tumor growth and metastasis. In syngeneic mouse models, tumors formed by LL2 cells overexpressing Oct4 were larger in volume, had shorter survival times, and contained a higher proportion of M2 macrophages. Additionally, treatment with all-trans retinoic acid (ATRA) significantly reduced tumor volume, extended mouse survival time, and decreased the proportion of M2 macrophages.

Compared to studies focusing solely on tumor cells, this research expands its scope to include the tumor microenvironment, providing a comprehensive analysis of the interactions between tumor cells and macrophages. This integrative approach facilitates a more thorough understanding of the mechanisms underlying tumor progression. By employing human inflammation antibody array technology, the study was able to simultaneously detect changes in multiple inflammatory factors, which is crucial for comprehending the cytokine network within the tumor microenvironment. Overall, the study innovatively reveals the role of Oct4 in the tumor microenvironment, proposing a new model of the Oct4-M-CSF-TAM axis. This model was validated through multiple levels of evidence, offering new perspectives and directions for future lung cancer therapies.

However, the study inevitably has some limitations and areas requiring further validation. Future research should increase the sample size, investigate the interactions of other cytokines, verify the role of the Oct4-M-CSF axis in different types of tumors, and conduct large-scale clinical studies. Additionally, developing and optimizing therapies targeting Oct4 and M-CSF is necessary. These efforts will contribute to a comprehensive understanding of the complex regulatory mechanisms within the tumor microenvironment, offering new insights and strategies for cancer treatment. Systematic and multi-faceted research is expected to further elucidate the complex regulatory mechanisms of the tumor microenvironment, potentially providing new approaches and strategies for cancer therapy.

Reference:

Lu, Chia-Sing, et al. "Oct4 promotes M2 macrophage polarization through upregulation of macrophage colony-stimulating factor in lung cancer." Journal of hematology & oncology 13 (2020): 1-16.