Sakae Maeda

Cell cycle-dependent Rho GTPase activity dynamically regulates cancer cell motility and invasion in vivo

The mechanism behind the spatiotemporal control of cancer cell dynamics and its possible association with cell proliferation has not been well established. By exploiting the intravital imaging technique, we found that cancer cell motility and invasive properties were closely associated with the cell cycle. In vivo inoculation of human colon cancer cells bearing fluorescence ubiquitination-based cell cycle indicator (Fucci) demonstrated an unexpected phenomenon: S/G2/M cells were more motile and invasive than G1 cells. Microarray analyses showed that Arhgap11a, an uncharacterized Rho GTPase-activating protein (RhoGAP), was expressed in a cell-cycle-dependent fashion. Expression of ARHGAP11A in cancer cells suppressed RhoA-dependent mechanisms, such as stress fiber formation and focal adhesion, which made the cells more prone to migrate. We also demonstrated that RhoA suppression by ARHGAP11A induced augmentation of relative Rac1 activity, leading to an increase in the invasive properties. RNAi-based inhibition of Arhgap11a reduced the invasion and in vivo expansion of cancers. Additionally, analysis of human specimens showed the significant up-regulation of Arhgap11a in colon cancers, which was correlated with clinical invasion status. The present study suggests that ARHGAP11A, a cell cycle-dependent RhoGAP, is a critical regulator of cancer cell mobility and is thus a promising therapeutic target in invasive cancers.

Prognostic impact of preoperative NLR and CA19-9 in pancreatic cancer

BACKGROUND Recently, several preoperative proinflammatory markers and nutritional factors such as neutrophil-to-lymphocyte ratio (NLR) and prognostic nutrition index (PNI) have been reported as significant predictor for poor prognosis of various malignant tumors. In this study, we evaluated the prognostic values of these preoperative parameters in patients with resectable pancreatic head cancer. METHODS We retrospectively reviewed consecutive patients who underwent PD for pancreatic head cancer between 2007 and 2012. A total of 46 patients were enrolled in this analysis. Preoperative parameters such as CRP, CA19-9, NLR and PNI at the time of presentation were recorded as well as overall survival. Cancer specific survival was assessed using Kaplan-Meier method. Univariate and multivariate Cox regression models were applied to evaluate the prognostic relevance of preoperative parameters. The correlations between CA19-9 values, NLR and pathological findings, first recurrence site were respectively reviewed. RESULTS In multivariable analysis preoperative high NLR (≧2.7) and high CA19-9 (≧230) were independent prognostic factors for poor survival (P value: 0.03 and 0.025, respectively). Kaplan-Meier survival analysis demonstrated the overall 2-year survival rate in patients with high NLR or high CA19-9 were 37.5% compared with 89.9% in patients with low NLR and low CA19-9. CONCLUSION Preoperative NLR and serum CA19-9 offer significant prognostic information associated with overall survival following PD in the patients with pancreatic head cancer.

Interferon-α acts on the S/G2/M phases to induce apoptosis in the G1 phase of an IFNAR2-expressing hepatocellular carcinoma cell line.

Background: The mode of action of interferon-α has been unknown. Results: Its point of action in the cell cycle was analyzed by single cell tracking using time lapse confocal imaging. Conclusion: Interferon-α activates p63 in S/G2/M and induces apoptosis and cell cycle arrest in the subsequent G1. Significance: Tracking cell cycle progression is crucial for understanding the mechanisms of interferon-α. Interferon-α (IFN-α) is used clinically to treat hepatocellular carcinoma (HCC), although the detailed therapeutic mechanisms remain elusive. In particular, IFN-α has long been implicated in control of the cell cycle, but its actual point of action has not been clarified. Here, using time lapse imaging analyses of the human HCC cell line HuH7 carrying a fluorescence ubiquitination-based cell cycle indicator (Fucci), we found that IFN-α induced cell cycle arrest in the G0/G1 phases, leading to apoptosis through an IFN-α type-2 receptor (IFNAR2)-dependent signaling pathway. Detailed analyses by time lapse imaging and biochemical assays demonstrated that the IFN-α/IFNAR2 axis sensitizes cells to apoptosis in the S/G2/M phases in preparation for cell death in the G0/G1 phases. In summary, this study is the first to demonstrate the detailed mechanism of IFN-α as an anticancer drug, using Fucci-based time lapse imaging, which will be informative for treating HCC with IFN-α in clinical practice.

Survival Impact of Pulmonary Metastasis as Recurrence of Pancreatic Ductal Adenocarcinoma

Aim: This study aimed at investigating the survival impact of pancreatic ductal adenocarcinoma (PDAC) recurrence as pulmonary metastasis. Methods: We performed a retrospective case-control study of 142 patients who underwent curative resection for PDAC at our institution between 2003 and 2012. Clinicopathological features were compared among patients stratified according to the recurrence pattern and pulmonary metastasis treatment strategy. Results: Patients underwent pancreaticoduodenectomy (n = 96), distal (n = 42), or total pancreatectomy (n = 4). At the last follow-up, 99 patients had developed recurrent post-resection PDAC, including 14 cases of isolated pulmonary recurrence. The median overall survival was significantly longer for patients with isolated pulmonary recurrence (40.3 months) than with other metastases (20.9 months; HR 5.85; p = 0.0156). Two patients underwent resection for isolated pulmonary recurrence, and both survived for ∼70 months after primary resection. Conclusion: Patients with first recurrence of PDAC as pulmonary metastasis had a better prognosis than patients with other types of metastases. Moreover, when isolated pulmonary metastasis is controlled for a certain period, pulmonary resection is likely to improve patient survival.

CA19-9 level determines therapeutic modality in pancreatic cancer patients with para-aortic lymph node metastasis

BACKGROUND In general, para-aortic lymph node (LN16) metastasis has been considered as a contraindication for pancreatic resection. However, some pancreatic cancer patients with LN16 metastasis have been reported to survive for longer than expected after pancreatectomy. The purpose of this study was to determine whether pancreatic cancer patients with LN16 metastasis might benefit from surgery. METHODS We retrospectively reviewed 201 consecutive patients with invasive pancreatic ductal adenocarcinoma who underwent surgery at Osaka National Hospital between April 2003 and December 2012. These patients included 22 patients with LN16 metastasis who underwent an extended lymphadenectomy and 25 patients who underwent a palliative surgical biliary and gastric bypass. The clinicopathological data and outcomes were evaluated using univariate and multivariate analyses. RESULTS The overall survival of the patients with LN16 metastasis was poorer than that of the LN16-negative patients (P = 0.0014). An overall survival analysis of the LN16-positive patients stratified according to the preoperative CA19-9 level showed a significant difference between patients with a low preoperative CA19-9 level (≤360 U/mL) and those with a high preoperative CA19-9 level (>360 U/mL) (P = 0.0301). No significant difference in overall survival of patients was observed between those with LN16 positivity and those who underwent bypass surgery. However, the overall survival of the LN16-positive patients with a CA19-9 level ≤360 U/mL (n = 11) was significantly higher than that of those who underwent bypass surgery (P = 0.0452). CONCLUSION Surgical resection and extended lymphadenectomy remains an option for pancreatic cancer patients with LN16-positivity whose CA19-9 level is ≤360 U/mL.

RFPL4A Increases the G1 Population and Decreases Sensitivity to Chemotherapy in Human Colorectal Cancer Cells

Background: Cell cycle-arrested cancer cells are resistant to conventional chemotherapy. Results: Microarray analyses showed that expression of RFPL4A was significantly up-regulated in these G1-retained cells. Conclusion: RFPL4A is a novel factor inducing G1 retention and reduced sensitivity to chemotherapy. Significance: Combination therapy using RFPL4A inhibition and conventional anti-cancer drugs may represent a promising therapeutic approach for intractable cancer patients. Cell cycle-arrested cancer cells are resistant to conventional chemotherapy that acts on the mitotic phases of the cell cycle, although the molecular mechanisms involved in halting cell cycle progression remain unclear. Here, we demonstrated that RFPL4A, an uncharacterized ubiquitin ligase, induced G1 retention and thus conferred decreased sensitivity to chemotherapy in the human colorectal cancer cell line, HCT116. Long term time lapse observations in HCT116 cells bearing a “fluorescence ubiquitin-based cell cycle indicator” identified a characteristic population that is viable but remains in the G1 phase for an extended period of time (up to 56 h). Microarray analyses showed that expression of RFPL4A was significantly up-regulated in these G1-arrested cells, not only in HCT116 cells but also in other cancer cell lines, and overexpression of RFPL4A increased the G1 population and decreased sensitivity to chemotherapy. However, knockdown of RFPL4A expression caused the cells to resume mitosis and induced their susceptibility to anti-cancer drugs in vitro and in vivo. These results indicate that RFPL4A is a novel factor that increases the G1 population and decreases sensitivity to chemotherapy and thus may be a promising therapeutic target for refractory tumor conditions.