Thyroid-specific enhancer-binding protein (T/ebp)/Nkx2.1-null mouse thyroids degenerate by embryonic day (E) 12-13 through apoptosis whereas T/ebp/Nkx2.1-heterogyzgous mice exhibit hypothyroidism with elevated TSH levels. To understand the role of T/ebp/Nkx2.1 in the adult thyroid, a thyroid follicular cell-specific conditional knockout (KO) mouse line, T/ebp(fl/fl);TPO-Cre, was established that expresses Cre recombinase under the human thyroid peroxidase (TPO) gene promoter. These mice appeared to be healthy and exhibited loss of T/ebp/Nkx2.1 expression in many, but not all, thyroid follicular cells as determined by immunohistochemistry and real-time PCR, thus presenting a T/ebp-thyroid-conditional hypomorphic mice. Detailed analysis of the thyroids from T/ebp(fl/fl), T/ebp(fl/fl);TPO-Cre, and T/ebp(fl/ko) mice, where the latter mouse line is derived from crosses with the original T/ebp/Nkx2.1-heterozygous mice, revealed that T/ebp(fl/fl);TPO-Cre mice can be classified into two groups with different phenotypes: one having atrophic/degenerative thyroid follicles with frequent presence of adenomas and extremely high serum TSH levels, and the other having an altered thyroid structure with reduced numbers of extraordinary dilated follicles consisting of excessive numbers of follicular cells as compared with those usually found in the normal thyroid. The latter phenotype was also observed in aged T/ebp(fl/ko) mouse thyroids. In vitro three-dimensional thyroid primary cultures using thyroids from T/ebp(fl/fl);TPO-Cre, T/ebp(fl/ko), and T/ebp(fl/fl) mice, and the latter treated with recombinant adenovirus with and without Cre expression, demonstrated that only cells from T/ebp(fl/fl) mice without adeno-Cre treatment formed follicular structures. Taken together, these results suggest that T/ebp/Nkx2.1 is required for maintenance of the normal architecture and function of differentiated thyroids.

We analyzed nucleotide sequence and intraclonal diversity of the rearranged immunoglobulin heavy chain gene variable region (VH gene) of CD5 + and CD5 − diffuse large B cell lymphoma (DLBCL) to clarify the cell origin of de novo CD5 + DLBCL. Ten cases of CD5 + DLBCL and 29 cases of CD5 − DLBCL were analyzed. The frequencies of somatic mutation were 0.7 to 12.9% (average, 6.2%) in CD5 + DLBCL and 2.0 to 25.9% (average, 11.1%) in CD5 − DLBCL. The ongoing mutation rate was estimated from the number of further single base-substitutions, expressed as a percentage of the total number of nucleotides in 10 cloned PCR products for each case (%). The averages of the ongoing mutation rate of CD5 + DLBCL (four cases) and CD5 − DLBCL (seven cases) were 0.051% and 0.197%, respectively. The rate of CD5 + DLBCL was significantly lower than that of CD5 − DLBCL (t-test, P = 0.024). These data may indicate that the cell origin of CD5 + DLBCL is different from that of CD5 − DLBCL. CD5 is not an activated antigen in DLBCL, but a specific marker of the B1 subset of the B cells, and de novo CD5 + DLBCL may therefore be derived from this unique subset. Leukemia (2001) 15, 452-457.

Metastatic renal cell carcinoma (mRCC) is a tumor entity with poor prognosis due to limited therapy options. Tyrosine kinase inhibitors (TKIs), the novel targeted agents have been used for the treatment of mRCC and have shown efficacy. Interferon (IFN)-α is also one of the most frequently used agents in immunotherapy. However, drug resistance needs to be overcome to achieve a sufficiently positive effect. Interleukin-6 (IL-6), which induce suppressor of cytokine signaling-3 (SOCS3) expression, is one of the factors associated with poor prognosis of patients with renal cell carcinoma (RCC). To analyze the influence of IL-6 in drug resistance of RCC, anti-IL-6 receptor antibody was used in combination with IFN or TKIs. The SOCS3 mRNA expression level was significantly increased by IFNα stimulation in 786-O RCC cells which were resistant to IFN, but not in ACHN cells that were sensitive to IFN. The overexpression of SOCS3 by gene transfection in ACHN significantly inhibited the growthinhibitory effect of IFNα. An in vivo study demonstrated that coadministration of SOCS3-targeted siRNA promoted INFαinduced cell death and growth suppression in 786-O cell xenograft. SOCS3 could be a key component in the resistance to interferon treatment of renal cell carcinoma. Because SOCS3 is rapidly upregulated by IL-6 and a negative regulator of cytokine signaling, IL-6 expression on RCC cells was also analyzed and the 786-O cells showed the high level of IL-6 mRNA expression under the condition of interferon stimulation. IL-6R antibody, tocilizumab, significantly suppressed cell proliferation in 786-O cells by interferon stimulation accompanied with phosphorylation of STAT1 and inhibited SOCS3 expression. The in vivo effects of combination therapy with tocilizumab and interferon showed significant suppression of 786-O tumor growth in a xenograft model. We also hypothesized that TKI resistance and IL-6 secretion are causally connected. And we found that 786-O RCC cells secrete high IL-6 levels after low dose stimulation with the TKIs sorafenib, sunitinib and pazopanib, inducing activation of AKT-mTOR pathway, NFκB, HIF-2α and VEGF expression. Tocilizumab neutralizes the AKT-mTOR pathway activation and results in reduced proliferation. A combination therapy with tocilizumab and TKI suppresses 786-O tumor growth and inhibits angiogenesis in vivo more efficient than TKI alone. Our findings suggest that IL-6 could induce drug resistance on RCC, and combination therapy of IL-6R inhibitors and IFN/TKIs may represent a novel therapeutic approach for RCC treatment.

Summary Primary peripheral T‐cell lymphoma, not otherwise specified (PTCL‐NOS) of the thyroid is an extremely rare neoplasm. Six cases of primary PTCL‐NOS of the thyroid were analysed for clinicopathological features and genomic alteration patterns using oligo‐array comparative genomic hybridization. All patients had a diffusely enlarged thyroid and three cases showed leukaemic manifestation. Five of the six cases had anti‐thyroid antibodies and the remaining case showed hypothyroidism, suggesting that all cases had autoimmune thyroiditis. Except for one early relapsed case, the remaining five patients are alive and three of these five individuals have survived for 70 months or more. Interestingly, two cases showed spontaneous regressions after partial thyroid biopsy without any therapy. Leukaemic manifestation disappeared after irradiation of the thyroid mass in another two cases. The tumour cells were positive for CD3, CD4 and CXCR3 in all cases, suggesting that the tumour cells are of a type 1 helper T‐cell origin. All six cases showed genomic alterations that were different from those previously reported for PTCL‐NOS. The loss of 6q24·2 was characteristic and was detected in four of the six cases. These results suggest that primary PTCL‐NOS of the thyroid arising from autoimmune thyroiditis is a distinct disease entity among heterogeneous PTCL‐NOS.