p63, a member of the p53 gene family, encodes multiple proteins that may either transactivate p53 responsive genes (TAp63) or act as a dominant-negative factor toward p53 and p73 (Delta Np63). p63 is expressed in many epithelial compartments and p63(-/-) mice fail to develop skin, prostate, and mammary glands among other defects. It has been previously shown that p63 is expressed in normal urothelium. This study reports that p63 is regulated in bladder carcinogenesis and that p63 expression is lost in most invasive cancers whereas papillary superficial tumors maintain p63 expression. Examination of bladder carcinoma cell lines reveals that certain lines derived from invasive carcinomas maintain expression of Delta Np63, as demonstrated by both immunoblotting and confirmed by isoform-specific quantitative reverse transcriptase-polymerase chain reaction. Another novel finding reported in this study is the fact that p63(-/-) mice develop a bladder mucosa epithelial layer yet fail to complete uroepithelial differentiation, producing a nontransitional default cuboidal epithelium. These data indicate that in contrast to the skin and prostate, p63 is not required for formation of a bladder epithelium but is indispensable for the specific differentiation of a transitional urothelium.

The ROMK (Kir1.1; Kcnj1) gene is believed to encode the apical small conductance K ؉ channels (SK) of the thick ascending limb (TAL) and cortical collecting duct (CCD). Loss-of-function mutations in the human ROMK gene cause Bartter's syndrome with renal Na ؉ wasting, consistent with the role of this channel in apical K ؉ recycling in the TAL that is crucial for NaCl reabsorption. However, the mechanism of renal K ؉ wasting and hypokalemia that develop in individuals with ROMK Bartter's syndrome is not apparent given the proposed loss of the collecting duct SK channel. Thus, we generated a colony of ROMK null mice with ϳ25% survival to adulthood that provides a good model for ROMK Bartter's syndrome. The remaining 75% of null mice die in less than 14 days after birth. The surviving ROMK null mice have normal gross renal morphology with no evidence of significant hydronephrosis, whereas non-surviving null mice exhibit marked hydronephrosis. ROMK protein expression was absent in TAL and CCD from null mice but exhibited normal abundance and localization in wild-type littermates. ROMK null mice were polyuric and natriuretic with an elevated hematocrit consistent with mild extracellular volume depletion. SK channel activity in TAL and CCD was assessed by patch clamp analysis in ROMK wild-type ROMK(؉/؉), heterozygous ROMK(؉/؊), and null ROMK(؊/؊) mice. In 313 patches with successful seals from the three ROMK genotypes, SK channel activity in ROMK (؉/؉ and ؉/؊) exhibited normal single channel kinetics. The expression frequencies are as follows: 67 (TAL) and 58% (CCD) in ROMK(؉/؉); about half that of the wild-type in ROMK(؉/؊), being 38 (TAL) and 25% (CCD); absent in both TAL or CCD in ROMK(؊/؊) between 2 and 5 weeks in 15 mice (61 and 66 patches, respectively). The absence of SK channel activity in ROMK null mice demonstrates that ROMK is essential for functional expression of SK channels in both TAL and CCD. Despite loss of ROMK expression, the normokalemic null mice exhibited significantly increased kaliuresis, indicating alternative mechanisms for K ؉ absorption/secretion in the nephron.

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Integrin ␣11 (ITGA11/␣11) is localized to stromal fibroblasts and commonly overexpressed in non-small-cell lung carcinoma (NSCLC). We hypothesized that stromal ␣11 could be important for the tumorigenicity of NSCLC cells. SV40 immortalized mouse embryonic fibroblasts established from wild-type (WT) and Itga11-deficient [knockout (KO)] mice were tested for their tumorigenicity in immune-deficient mice when implanted alone or coimplanted with the A549 human lung adenocarcinoma cells. A549 coimplanted with the fibroblasts showed a markedly enhanced tumor growth rate compared with A549, WT, or KO, which alone formed only small tumors. Importantly, the growth was significantly greater for A549؉WT compared with A549؉KO tumors. Reexpression of human ␣11 cDNA in KO cells rescued a tumor growth rate to that comparable with the A549؉WT tumors. These findings were validated in two other NSCLC cell lines, NCI-H460 and NCI-H520. Gene expression profiling indicated that IGF2 mRNA expression level was >200 times lower in A549؉KO compared with A549؉WT tumors. Stable short-hairpin RNA (shRNA) down-regulation of IGF2 in WT (WT shIGF2) fibroblasts resulted in a decreased growth rate of A549؉WTshIGF2, compared with A549؉WT tumors. The results indicate that ␣11 is an important stromal factor in NSCLC and propose a paradigm for carcinoma-stromal interaction indirectly through interaction between the matrix collagen and stromal fibroblasts to stimulate cancer cell growth.cancer-associated fibroblast ͉ tumor microenvironment ͉ tumor progression ͉ tumor-stromal interaction ͉ paracrine signaling