Dual role of CD73 as a signaling molecule and adenosine-generating enzyme in colorectal cancer progression and immune evasion.

Metastasis and limited benefits of immune checkpoint blockade are two obstacles to the battle against colorectal cancer (CRC). CD73, encoded by the gene 5'-Nucleotidase Ecto (NT5E), is a major enzyme that generates extracellular adenosine. However, whether CD73 affects cancer progression and immune response in CRC remains unclear. Here, the clinical significance of CD73 was assessed in human CRC specimens using immunohistochemistry and bioinformatic analyses. We demonstrated that CD73 is elevated in CRC tissues, particularly in those with metastasis, and correlates with poor prognosis. Gain- and loss-of-function experiments demonstrate that tumor CD73 supports tumor progression and impairs the viability and effector functions of CD8+ T cells. Targeting CD73 on CRC cells reduces their malignant phenotypes and improves the anti-cancer response of CD8+ T cells in the tumor microenvironment (TME). Moreover, the combination of CD73 blockade and PD-1 inhibitors exhibited enhanced anti-cancer effects when compared to a single-agent treatment. Thus, CD73 may be a promising target in the treatment of CRC.

Pharmacological targeting PTK6 inhibits the JAK2/STAT3 sustained stemness and reverses chemoresistance of colorectal cancer.

BACKGROUND: Chemoresistance is the major cause of chemotherapy failure in patients with colorectal cancer (CRC). Protein tyrosine kinase 6 (PTK6) is aberrantly overexpressed in clinical CRC tissues undergoing chemotherapy. We studied if PTK6 contributed to the chemoresistance of CRC in human and mice. METHODS: We obtained tissue samples from patients with CRC and measured the expression of PTK6 by immunohistochemistry. Gain- and loss-of-function assays were performed to study the biological functions of PTK6. We constructed the FLAG-tagged wild type (WT), kinase-dead, and inhibition-defective recombinant mutants of PTK6 to study the effect phosphorylated activation of PTK6 played on CRC cell stemness and chemoresistance. We used small molecule inhibitor XMU-MP-2 to test the influence of PTK6 on sensitivity of CRC cells to 5-FU/L-OHP in both nude mouse and patient-derived xenograft (PDX) animal models. RESULTS: PTK6 is overexpressed in CRC tissues and plays a stimulatory role in the proliferation and chemoresistance of CRC cells both in vitro and in vivo. PTK6, especially the phosphorylated PTK6, can promote the stemness of CRC cells through interacting with JAK2 and phosphorylating it to activate the JAK2/STAT3 signaling. Pharmacological inhibition of PTK6 using XMU-MP-2 effectively reduces the stemness property of CRC cells and improves its chemosensitivity to 5-FU/L-OHP in both nude mice subcutaneously implanted tumor model and PDX model constructed with NOD-SCID mice. CONCLUSIONS: PTK6 interacts with JAK2 and phosphorylates it to activate JAK2/STAT3 signaling to promote the stemness and chemoresistance of CRC cells. Pharmacological inhibition of PTK6 by small molecule inhibitor dramatically enhances the sensitivity to chemotherapy in nude mice and PDX models.

LIMK1 nuclear translocation promotes hepatocellular carcinoma progression by increasing p-ERK nuclear shuttling and by activating c-Myc signalling upon EGF stimulation.

LIM kinase 1 (LIMK1) is a serine/threonine and tyrosine kinase that is predominantly located in the cytoplasm. In our study, nuclear translocation of LIMK1 in clinical hepatocellular carcinoma (HCC) samples was demonstrated for the first time, especially in samples from those with intravascular tumour thrombus. LIMK1 was overexpressed in HCC tissues, and nuclear LIMK1 expression was associated with poor prognosis in HCC patients. Although the effects of cytoplasmic LIMK1 on cofilin phosphorylation and actin filament dynamics have been well studied, the function of nuclear LIMK1 is still unclear. Gain- and loss-of-function experiments were performed both in vitro and in vivo and demonstrated a correlation between nuclear LIMK1 and the enhanced aggressive phenotype of HCC. EGF could drive the nuclear translocation of LIMK1 by activating the interaction of p-ERK and LIMK1 and facilitating their roles in nuclear shuttling. Moreover, nuclear LIMK1 could directly bind to the promoter region of c-Myc and stimulate c-Myc transcription. Although the EGFR monoclonal antibody cetuximab has a poor therapeutic effect on advanced HCC patients, in vivo animal study showed that cetuximab achieved a significant inhibitory effect on the progression of nuclear LIMK1-overexpressing HCC cells. In addition, recent data have demonstrated the potential of cetuximab in combination therapy for HCC patients with LIMK1 nuclear translocation.

Long noncoding RNA CRCMSL suppresses tumor invasive and metastasis in colorectal carcinoma through nucleocytoplasmic shuttling of HMGB2.

Long noncoding RNAs (lncRNAs) are pervasive transcripts that play pivotal roles in regulating chromatin dynamics, gene and protein expression. Aberrant expression and mutations of lncRNAs represent a driving force behind tumor invasion and metastasis, making them attractive cancer targets. However, most of the lncRNAs are still being discovered and conclusive experimental evidence for their functional relevance is still lacking for most malignancies. In this study, a differentially expressed lncRNA, designated as lnc-CRCMSL, is identified by microarray-based screenings on non-metastatic and metastatic CRC specimens. Lnc-CRCMSL is verified as an anti-metastatic gene and negatively correlated with the poor prognosis of CRC patients. Lnc-CRCMSL overexpression restricts tumor growth and metastasis in vivo and in vitro. Instead, lnc-CRCMSL silencing accelerates CRC cell proliferation and migration. RNA-pulldown assay identifies high mobility group box 2 (HMGB2) as a downstream protein of lnc-CRCMSL. Mechanically, lnc-CRCMSL physically binds to HMGB2 and stabilizes the localization of HMGB2 in the cytoplasm. Notably, lnc-CRCMSL knockdown lead to the shift of HMGB2 into nuclear, in which it triggers epithelial to mesenchymal transition (EMT) programming. Importantly, lnc-CRCMSL controls the cytoplasmic retention of HMGB2 and attenuates the interaction between HMGB2 and OCT4 to suppress EMT. Treatment of leptomycin B (LMB), a potent and specific nuclear export inhibitor, counteracts lnc-CRCMSL-mediated suppression of aggressive phenotypes and EMT process by accumulating the nuclear HMGB2. CONCLUSION: Our data highlight the anti-metastatic role of lnc-CRCMSL in stabilizing HMGB2 through lncRNA-protein interactions in the cytoplasm, and suggest that targeting lnc-CRCMSL may represent a therapeutic opportunity for managing metastatic CRC.