Krüppel-like factor 4 (KLF4) is highly expressed in epithelial tissues such as the gut and skin. However, the role of KLF4 in human gastric cancer development and progression is unknown. Here we show that KLF4 protein expression was decreased or lost in primary tumors and, in particular, lymph node metastases when compared with that in normal gastric mucosa. Moreover, loss of KLF4 expression in the primary tumors was significantly associated with poor survival, and also an independent prognostic marker in a multivariate analysis. Consistently, most human gastric cancer cell lines exhibited loss of or a substantial decrease in KLF4 expression at both RNA and protein levels. Enforced restoration of KLF4 expression resulted in marked cell growth inhibition in vitro and significantly attenuated tumor growth and total abrogation of metastasis in an orthotopic animal model of gastric cancer. Mechanism studies indicated that promoter hypermethylation and hemizygous deletion contributed to the down-regulation of KLF4 expression and the induction of apoptosis contributed to the antitumor activity of KLF4. Collectively, our data provide first clinical and casual evidence and potential mechanism that the alteration of KLF4 expression plays a critical role in gastric cancer development and progression.

Krüppel-like transcriptional factor is important in maintaining cellular functions. Deletion of Krüppel-like transcriptional factor usually causes abnormal embryonic development and even embryonic death. KLF4 is a prominent member of this family, and embryonic deletion of KLF4 leads to alterations in skin permeability and postnatal death. In addition to its important role in embryo development, it also plays a critical role in inflammation and malignancy. It has been investigated that KLF4 has a regulatory role in a variety of cancers, including lung, breast, prostate, colorectal, pancreatic, hepatocellular, ovarian, esophageal, bladder and brain cancer. However, the role of KLF4 in tumorigenesis is complex, which may link to its unique structure with both transcriptional activation and transcriptional repression domains, and to the regulation of its upstream and downstream signaling molecules. In this review, we will summarize the structural and functional aspects of KLF4, with a focus on KLF4 as a clinical biomarker and therapeutic target in different types of tumors.

Tight junction (TJ) is the barrier of epithelial and endothelial cells to maintain paracellular substrate transport and cell polarity. As one of the TJ cytoplasmic adaptor proteins adjacent to cell membrane, zonula occludens (ZO) proteins are responsible for connecting transmembrane TJ proteins and cytoplasmic cytoskeleton, providing a binding platform for transmembrane TJ proteins to maintain the barrier function. In addition to the basic structural function, ZO proteins play important roles in signal regulation such as cell proliferation and motility, the latter including cell migration, invasion and metastasis, to influence embryonic development, tissue homeostasis, damage repair, inflammation, tumorigenesis, and cancer progression. In this review, we will focus on the signal regulating function of ZO proteins in inflammation and tumorigenesis, and discuss the limitations of previous research and future challenges in ZO protein research.

Purpose: Pancreatic ductal adenocarcinoma (PDA) resists immunotherapy of adoptive cell transfer (ACT) and immune checkpoint inhibitors. Understanding the mechanisms underlying this resistance will improve PDA immunotherapy. This study investigated therapeutic effects and underlying mechanisms of anticoagulants on immunotherapy in PDA. Experimental Design: The antitumor activity of immunotherapy was evaluated in mouse models of desert, excluded, and inflamed tumors. The underlying mechanisms were investigated by analyzing immune cell infiltration by immunofluorescence imaging and tumor microcirculation by interstitial fluid pressure and coagulation status measurement. Results: Combined use of heparin and ACT inhibited tumor growth and metastasis, whereas neither heparin nor ACT had any therapeutic effect. The combination of heparin and ACT significantly increased the intratumor infiltration of CD8+ T cells and M1 macrophages and reduced the infiltration of immunosuppressive M2 macrophages and FOXP3+/CD4+ regulatory T cells (Treg). Assessments of tumor microenvironment revealed that heparin promoted tumor vascular regression and normalized the remaining blood vessels, facilitating the extravasation and perivascular accumulation of activated CD8+ T cells in tumors. Mechanistically, tumor microvessel hemodynamic properties were significantly improved by heparin, which is consistent with its inhibitory effects on tumor angiogenesis. Similarly, the combination of heparin and anti-PD1 also produced a pronounced antitumor activity, whereas neither heparin nor anti-PD1 treatment had appreciable antitumor activity. Conclusions: Combined treatment of heparin and ACT or anti-PD1 produced synergistic antitumor effects, which were at least in part through tumor vascular normalization, hence increased antitumor T-cell responses due to reduced Treg infiltration and increased M1 macrophage polarization. This synergistic combination therapy warrants clinical evaluation. See related commentary by Korc, p. 2348