Furthermore, we observed an increased nuclear S100A15 3,4,5-Trimethoxyphenylacetic acid expression in lung cancer tissues not only in stage IV NSCLC compared to stage IIIB NSCLC, but also in the patients with stable or progressive disease in comparison to those with a partial response after first line combination chemotherapy with CDDP and GEM. Additionally, a high percentage of S100A15 nuclear Tulathromycin B stained cells was the only independent factor associated with three-year overall survival. This suggests that nuclear accumulation of S100A15 may be linked to metastasis potential, treatment response, and long-term outcomes. In accordance with the results published in the Human Protein Atlas website, 
we found up-regulation of S100A15 in NSCLC cancer tissues compared to normal lung tissues surrounding the tumor. Nonetheless, S100A15 in either cancer tissues or PBMC could not distinguish AC from SCC in this small sample-size study. Additionally, quantitative RT-PCR result for S100A15 was positively correlated with cytoplasmic S100A15 staining intensity score but not with other parameters in IHC staining assessment, implying that cytoplasmic protein expression rather than nuclear protein expression may affect S100A15 expression in peripheral immune cells, such as monocyte. Disruption of the calcium signaling pathway, such as by the S100 family, has been implicated as a central mechanism in tumorigenesis, specifically tumor invasion and metastasis. Both S100A15 and S100A7 proteins have been demonstrated to be distinctly expressed in normal breast tissue and breast cancer. Since S100A15 was found to be chemotactic for both granulocytes and monocytes, and to act synergistically with highly homologous S100A7 to enhance inflammation, both proteins could influence lung tumor progression. Additionally, E. coli can modulate the human S100A15 expression of keratinocytes by recognition through TLR4, suggesting that S100A15 may play a role in innate immunity. Selective expression of S100A7 in lung SCC and large cell carcinomas has been demonstrated, but not in AC or small cell carcinomas. Nuclear accumulation of S100A7 has been reported to be associated with a poor prognosis in head and neck cancer. To the best of our knowledge, the current study is the first to demonstrate that nuclear accumulation of S100A15 may be linked to an increased risk of distant metastasis, and that S100A15 may serve as a candidate biomarker for predicting treatment response and survival. However, large scale longitudinal studies are warranted to evaluate the potential of S100A15 as a determinant of advanced tumor stage and/or a predictor of long-term outcomes in NSCLC. Stimulation with TLR7 agonists on human lung cancer cells has been shown to lead to increased tumor cell survival and chemoresistance. On the other hand, systemic administration of TLR7 agonists has also been found to induce significant antitumor activity, which could be potentiated by cyclophosphamide. In a cell culture model, TLR7 agonists were found to enhance tumor cell lysis by human gamma delta T cells. Taken together, these findings suggest that enhancing the TLR7 expression in immune cells may potentiate the antitumor effect of combination chemotherapy in advanced stage NSCLC patients.