Adiponectin and Breast Cancer Figure 2. Reduced tumor latency in adiponectin haplodeficient MMTV-PyVT mice of both FVB/N and C57BL/6J genetic backgrounds. The tumor onset was closely monitored by visual inspection and palpation every 2–3 days. Latency of mammary tumors was defined as the age when a palpable lump was first detected in the mammary gland. Kaplan-Meier estimates of the tumor-free survival curves were calculated and plotted. Median value represents the time point when 50% of animals developed palpable tumor masses. The significance of differences in latency was analyzed by the Log-rank test. The comparisons were performed between ADN(+/+) and ADN(+/2) female (left panel) and male (right panel) animals in FVB/N and C57BL/6J genetic backgrounds. CI, confidence interval. doi:10.1371/journal.pone.0004968.g002 231 human breast cancer cells [28]. To investigate whether adiponectin inadequacy could enhance beta-catenin signaling in mammary tumors, we examined the phosphorylation status of GSK3beta and its upstream protein kinase Akt, as well as the protein levels and nuclear activities of beta-catenin (Figure 7A). The results revealed that in primary tumor cells derived from PyVT(+/2)/ADN(+/2) mice, phosphorylations of both Akt at serine 473 and GSK3beta at serine 9 were significantly increased. On the other hand, the phosphorylation of ERK1/2 was not different between the two types of tumor cells from PyVT(+/2)/ ADN(+/+) and PyVT(+/2)/ADN(+/2) mice (data not shown). The protein levels of beta-catenin and its target cyclin D1 were largely elevated. The augmented beta-catenin signaling was also confirmed by measuring its nuclear activities, which were increased by ,4.5 folds in PyVT(+/2)/AND(+/2) tumor cells according to the results from the TOPflash/FOPflash reporter PLoS ONE | www.plosone.org 4 March 2009 | Volume 4 | Issue 3 | e4968