The WT1 gene encoding a zinc finger polypeptide is a tumor suppressor gene that plays a key role in the carcinogenesis of Wilms' tumor. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to examine relative levels of WT1 gene expression (defined in K562 cells as 1.00) in 45 patients with acute myelogenous leukemia (AML), 22 with acute lymphocytic leukemia (ALL), 6 with acute mixed lineage leukemia (AMLL), 23 with chronic myelogenous leukemia (CML), and 24 with non- Hodgkin's lymphoma. Significant levels of WT1 gene were expressed in all leukemia patients and for CML the levels increased as the clinical phase progressed. In striking contrast with acute leukemia, the levels of WT1 gene expression for NHL were significantly lower or even undetectable. Clear correlation was observed between the relative levels of WT1 gene expression (< 0.6 v > or = 0.6) and the prognosis for acute leukemia (AML, ALL, and AMLL). Patients with less than 0.6 levels had significantly higher rates of complete remission (CR), disease-free survival, and overall survival than those with > or = 0.6 levels, whereas CR could not be induced in any of the 7 patients with acute leukemia having greater than 1.0 levels of WT1 gene expression. The quantitation of the WT1 gene expression made it possible to detect minimal residual disease (MRD) in acute leukemia regardless of the presence or absence of tumor-specific DNA markers. Continuous monitoring of the WT1 mRNA was performed for 9 patients with acute leukemia. In 4 patients, MRD was detected 2 to 8 months before clinical relapse became apparent. In 2 other patients, the WT1 mRNA gradually increased after discontinuation of chemotherapy. No MRD was detected in the remaining 3 patients with AML who received intensive induction and consolidation therapy. Simultaneous monitoring of MRD by RT-PCR using primers for specific DNA markers in 3 patients (2 AML-M3 with PML/RAR alpha, and 1 AML-M2 with AML1/ETO) among these 9 patients detected MRD comparable with that obtained from quantitation of WT1 gene expression. In a patient with acute promyelocytic leukemia, the limits of leukemic cell detection by RT-PCR using either WT1 or promyelocytic leukemia/retinoic acid receptor-alpha gene primers were 10(-3) to 10(- 4) and 10(-4) for bone marrow, and 10(-5) and 10(-4) for peripheral blood, respectively. Therefore, we conclude that WT1 is a new prognostic factor and a new marker for the detection of MRD in acute leukemia.

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Severe trochlear dysplasia is the most important predictor of residual patellofemoral instability after isolated MPFL reconstruction. In addition, an increased TT-TG distance affected the outcomes in patients with type D trochlea. Additional patellar stabilization procedures should be considered for patients with severe trochlear dysplasia and an increased TT-TG distance.

Chondrogenesis is a well‐coordinated multi‐step differentiation process in which resting chondrocytes produce terminally differentiated hypertrophic chondrocytes through a proliferative stage. Here we show that phosphoinositide‐3 kinase (PI3K) and its major downstream molecule, Akt, a serine–threonine kinase, play pivotal roles in this process. Akt signaling was activated in resting and proliferative chondrocytes but was reduced during terminal differentiation. We adopted two chondrocyte differentiation systems to investigate the roles of PI3K/Akt signaling in chondrogenesis. First, we employed an embryonic forelimb organ culture of transgenic mice expressing an Akt‐Mer (a ligand‐binding domain of a mutated estrogen receptor) fusion protein whose kinase activity was conditionally activated by treatment with 4‐hydroxytamoxifen (4OHT). Activation of Akt signaling in embryonic chondrogenesis enhanced chondrocyte proliferation and inhibited hypertrophic differentiation, presumably due to the suppressed expression of Runx2, a transcription factor critical for chondrocyte terminal differentiation. Conversely, inhibition of PI3K by its inhibitor accelerated terminal hypertrophic differentiation, resulting in a shorter bone. Essentially the same results were obtained in a second line of experiments using human synovial stromal cells (hSSCs), which are mesenchymal progenitor cells isolated from adult joints. These findings demonstrate that PI3K/Akt signaling is a key regulator in terminal chondrocyte differentiation in both embryonic and adult chondrogenesis.

IV.