The role of β-catenin in thymocyte development has been extensively studied, however, the function of β-catenin in thymic epithelial cells (TECs) remains largely unclear. Here, we demonstrate a requirement for β-catenin in keratin 5 (K5)-expressing TECs, which comprise the majority of medullary TECs (mTECs) and a progenitor subset for cortical TECs (cTECs) in the young adult thymus. We found that conditionally ablated β-catenin in K5(+)-TECs and their progeny cells resulted in thymic atrophy. The composition of TECs was also aberrantly affected. Percentages of K5(hi)K8(+)-TECs, K5(+)K8(-)-TECs and UEA1(+)-mTECs were significantly decreased and the percentage of K5(lo)K8(+)-TECs and Ly51(+)-cTECs were increased in β-catenin-deficient thymi compared with that in the control thymi. We also observed that β-catenin-deficient TEC lineage could give rise to K8(+)-cTECs more efficiently than wild-type TECs using lineage-tracing approach. Importantly, the expression levels of several transcription factors (p63, FoxN1 and Aire), which are essential for TEC differentiation, were altered in β-catenin-deficient thymi. Under the aberrant differentiation of TECs, development of all thymocytes in β-catenin-deficient thymi was impaired. Interleukin-7 (IL-7) and chemokines (Ccl19, Ccl25 and Cxcl12) levels were also downregulated in the thymic stromal cells in the mutants. Finally, introducing a BCL2 transgene in lymphoid lineages, which has been shown to rescue IL-7-deficient thymopoiesis, partially rescued the thymic atrophy and thymocyte development defects caused by induced ablation of β-catenin in K5(+)-TECs. Collectively, these findings suggest that β-catenin is required for the differentiation of TECs, thereby contributing to thymocyte development in the postnatal thymus.

The applicability of the International Staging System (ISS) for Chinese patients with multiple myeloma (MM) has not been demonstrated, especially with respect to treatments with novel agents. Newly diagnosed MM patients at Taipei Veterans General Hospital were enrolled between 1996 and 2007. Data regarding clinical features, laboratory tests, and outcome at last follow-up were collected. A total of 389 MM patients (71% male) were enrolled, with median age of 71 years. At diagnosis, 72.7% had Durie-Salmon (DS) stage III disease, 56.2% had ISS stage III disease, and 34% had serum creatinine ≧2.0 mg/dL. Compared with patients diagnosed in the first calendar period 1996-2001, the patients of the second calendar period 2002-2007 were older and more of these patients had received novel agents, especially thalidomide. The median overall survival period was 20.5 months, with a significant increase of patients in the second calendar period (15.3 and 28.2 months, respectively; P = 0.002), especially for those with ISS stages I and II. In the Cox proportion model, elevated serum β(2) microglobulin at diagnosis (≧3.5 mg/L), old age (≧65 years), and impaired renal function were found to be independently associated with poor survival. Over the entire period, the ISS was found to be effective in providing an accurate prognosis with respect to different ages and calendar periods. This is the first study to show the applicability of ISS for Chinese patients with MM, especially for those who had received thalidomide.

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