Burkhard Kneitz

Mammalian MutS homologue 5 is required for chromosome pairing in meiosis

MSH5 (MutS homologue 5) is a member of a family of proteins known to be involved in DNA mismatch repair. Germline mutations in MSH2, MLH1 and GTBP (also known as MSH6) cause hereditary non–polyposis colon cancer (HNPCC) or Lynch syndrome. Inactivation of Msh2, Mlh1, Gtmbp (also known as Msh6) or Pms2 in mice leads to hereditary predisposition to intestinal and other cancers. Early studies in yeast revealed a role for some of these proteins, including Msh5, in meiosis. Gene targeting studies in mice confirmed roles for Mlh1 and Pms2 in mammalian meiosis. To assess the role of Msh5 in mammals, we generated and characterized mice with a null mutation in Msh5. Msh5–/– mice are viable but sterile. Meiosis in these mice is affected due to the disruption of chromosome pairing in prophase I. We found that this meiotic failure leads to a diminution in testicular size and a complete loss of ovarian structures. Our results show that normal Msh5 function is essential for meiotic progression and, in females, gonadal maintenance.

Caveolin-2-Deficient Mice Show Evidence of Severe Pulmonary Dysfunction without Disruption of Caveolae

ABSTRACT Caveolin-2 is a member of the caveolin gene family with no known function. Although caveolin-2 is coexpressed and heterooligomerizes with caveolin-1 in many cell types (most notably adipocytes and endothelial cells), caveolin-2 has traditionally been considered the dispensable structural partner of the widely studied caveolin-1. We now directly address the functional significance of caveolin-2 by genetically targeting the caveolin-2 locus (Cav-2) in mice. In the absence of caveolin-2 protein expression, caveolae still form and caveolin-1 maintains its localization in plasma membrane caveolae, although in certain tissues caveolin-1 is partially destabilized and shows modestly diminished protein levels. Despite an intact caveolar membrane system, the Cav-2-null lung parenchyma shows hypercellularity, with thickened alveolar septa and an increase in the number of endothelial cells. As a result of these pathological changes, these Cav-2-null mice are markedly exercise intolerant. Interestingly, these Cav-2-null phenotypes are identical to the ones we and others have recently reported for Cav-1-null mice. As caveolin-2 expression is also severely reduced in Cav-1-null mice, we conclude that caveolin-2 deficiency is the clear culprit in this lung disorder. Our analysis of several different phenotypes observed in caveolin-1-deficient mice (i.e., abnormal vascular responses and altered lipid homeostasis) reveals that Cav-2-null mice do not show any of these other phenotypes, indicating a selective role for caveolin-2 in lung function. Taken together, our data show for the first time a specific role for caveolin-2 in mammalian physiology independent of caveolin-1.

Haploinsufficiency of Flap endonuclease (Fen1) leads to rapid tumor progression

Flap endonuclease (Fen1) is required for DNA replication and repair, and defects in the gene encoding Fen1 cause increased accumulation of mutations and genome rearrangements. Because mutations in some genes involved in these processes cause cancer predisposition, we investigated the possibility that Fen1 may function in tumorigenesis of the gastrointestinal tract. Using gene knockout approaches, we introduced a null mutation into murine Fen1. Mice homozygous for the Fen1 mutation were not obtained, suggesting absence of Fen1 expression leads to embryonic lethality. Most Fen1 heterozygous animals appear normal. However, when combined with a mutation in the adenomatous polyposis coli (Apc) gene, double heterozygous animals have increased numbers of adenocarcinomas and decreased survival. The tumors from these mice show microsatellite instability. Because one copy of the Fen1 gene remained intact in tumors, Fen1 haploinsufficiency appears to lead to rapid progression of cancer.

Expression of microRNA‐221 is progressively reduced in aggressive prostate cancer and metastasis and predicts clinical recurrence

Emerging evidence shows that microRNAs (miR) are involved in the pathogenesis of a variety of cancers, including prostate carcinoma (PCa). Little information is available regarding miR expression levels in lymph node metastasis of prostate cancer or the potential of miRs as prognostic markers in this disease. Therefore, we analyzed the global expression of miRs in benign, hyperplastic prostate tissue (BPH), primary PCa of a high risk group of PCa patients, and corresponding metastatic tissues by microarray analysis. Consistent with the proposal that some miRs are oncomirs, we found aberrant expression of several miRs, including the downregulation of miR‐221, in PCa metastasis. Downregulation of miR‐221 was negatively correlated with the expression of the proto‐oncogen c‐kit in primary carcinoma. In a large study cohort, the prostate‐specific oncomir miR‐221 was progressively downregulated in aggressive forms of PCa. Downregulation of miR‐221 was associated with clinicopathological parameters, including the Gleason score and the clinical recurrence during follow up. Kaplan–Meier estimates and Cox proportional hazard models showed that miR‐221 downregulation was linked to tumor progression and recurrence in a high risk prostate cancer cohort. Our results showed that progressive miR‐221 downregulation hallmarks metastasis and presents a novel prognostic marker in high risk PCa. This suggests that miR‐221 has potential as a diagnostic marker and therapeutic target in PCa.

Siglec-G is a B1 cell-inhibitory receptor that controls expansion and calcium signaling of the B1 cell population.

B1 cells are an important cell population for the production of natural antibodies and for antibacterial immunoglobulin responses. Here we identified the mouse protein Siglec-G as a B1 cell inhibitory receptor. Siglec-G was expressed in a B cell–restricted way, with large amounts present in B1 cells. When overexpressed, Siglec-G inhibited B cell receptor–mediated calcium signaling. Siglec-G-deficient mice had massive expansion of the B1a cell population, which began early in development and was B cell intrinsic. Siglec-G-deficient mice had higher titers of natural IgM antibodies but not a higher penetrance of IgG autoantibodies. Siglec-G-deficient B1 cells showed a strongly enhanced calcium signaling. Our results demonstrate that Siglec-G-dependent negative regulation exists in B1 cells, which may explain the naturally muted signaling response of B1 cells.

Outcome Predictors of Radical Prostatectomy in Patients With Prostate-Specific Antigen Greater Than 20 ng/ml: A European Multi-Institutional Study of 712 Patients

BACKGROUND Prostate cancer (PCa) patients with pretreatment prostate-specific antigen (PSA) >20 ng/ml have a high risk of biochemical and clinical failure and even cancer-related death after local therapy. Pretreatment predictors of outcome after radical prostatectomy (RP) in this patient group are necessary. OBJECTIVE Our aim was to assess how the use of additional high-risk factors (biopsy Gleason score [bGS] > or = 8 or clinical stage 3-4) can improve prediction of treatment failure and cancer-related death after RP in patients with PSA >20. DESIGN, SETTING, AND PARTICIPANTS In a retrospective multicentre cohort study from six European centres between 1987 and 2005, 712 patients with PSA >20 ng/ml underwent RP and bilateral pelvic lymphadenectomy. MEASUREMENTS Subgroups were analysed to determine the relationship between the number of high-risk factors and histopathology, biochemical progression-free survival, clinical evidence of progressive disease, prostate cancer-specific mortality (PCSM), and overall mortality. Kaplan-Meier analysis with log-rank test and Cox multivariable analysis were applied. RESULTS AND LIMITATIONS Median follow-up was 77 mo. The number of high-risk factors was significantly associated with unfavourable histopathology. Among patients with only PSA >20 ng/ml, 33% had pT2 PCa, 57.9% had bGS <7, 54% had negative surgical margins, and 85% were lymph node negative (pN0), whereas among patients with all three high-risk factors, 4.5% had pT2 PCa, 2.3% had bGS <7, 20.5% had negative margins, and 49% were pN0 (p<0.001). The strongest predictor of progression and mortality was bGS. PSA >20 ng/ml associated with bGS < or =7 resulted in 10-yr PCSM of 5%; when associated with bGS > or =8, PCSM was 35%. The main limitations of the study were retrospective design and varying treatment modalities. CONCLUSIONS PCa patients with PSA >20 ng/ml have varying risk levels of disease progression and PCSM. Considering additional risk factors further stratifies this group into four subgroups that can guide the clinician in preoperative patient counselling.

Hey Basic Helix-Loop-Helix Transcription Factors Are Repressors of GATA4 and GATA6 and Restrict Expression of the GATA Target Gene ANF in Fetal Hearts

ABSTRACT The Hey basic helix-loop-helix transcription factors are downstream effectors of Notch signaling in the cardiovascular system. Mice lacking Hey2 develop cardiac hypertrophy, often associated with congenital heart defects, whereas combined Hey1/Hey2 deficiency leads to severe vascular defects and embryonic lethality around embryonic day E9.5. The molecular basis of these disorders is poorly understood, however, since target genes of Hey transcription factors in the affected tissues remain elusive. To identify genes regulated by Hey factors we have generated a conditional Hey1 knockout mouse. This strain was used to generate paired Hey2- and Hey1/2-deficient embryonic stem cell lines. Comparison of these cell lines by microarray analysis identified GATA4 and GATA6 as differentially expressed genes. Loss of Hey1/2 leads to elevated GATA4/6 and ANF mRNA levels in embryoid bodies, while forced expression of Hey factors strongly represses expression of the GATA4 and GATA6 promoter in various cell lines. In addition, the promoter activity of the GATA4/6 target gene ANF was inhibited by Hey1, Hey2, and HeyL. Protein interaction and mutation analyses suggest that repression is due to direct binding of Hey proteins to GATA4 and GATA6, blocking their transcriptional activity. In Hey2-deficient fetal hearts we observed elevated mRNA levels of ANF and CARP. Expression of ANF and Hey2 is normally restricted to the trabecular and compact myocardial layer, respectively. Intriguingly, loss of Hey2 leads to ectopic ANF expression in the compact layer, suggesting a direct role for Hey2 in limiting ANF expression in this cardiac compartment.

Identifying the Best Candidate for Radical Prostatectomy Among Patients with High-Risk Prostate Cancer

BACKGROUND The current role of radical prostatectomy (RP) in patients with high-risk disease remains controversial. OBJECTIVE To identify which high-risk prostate cancer (PCa) patients might have favorable pathologic outcomes when surgically treated. DESIGN, SETTING, AND PARTICIPANTS We evaluated 1366 patients with high-risk PCa (ie, at least one of the following risk factors: prostate-specific antigen [PSA]>20 ng/ml, cT3, biopsy Gleason 8-10) treated with RP and pelvic lymph node dissection (PLND) at eight European centers between 1987 and 2009. A favorable pathologic outcome was defined as specimen-confined (SC) disease-namely, pT2-pT3a, node negative PCa with negative surgical margins. INTERVENTION All patients underwent radical retropubic prostatectomy and PLND. MEASUREMENTS Univariable and multivariable logistic regression models tested the association between predictors and SC disease. A logistic regression coefficient-based nomogram was developed and internally validated using 200 bootstrap resamples. The Kaplan-Meier method was used to depict biochemical recurrence (BCR) and cancer-specific survival (CSS) rates. RESULTS AND LIMITATIONS Overall, 505 of 1366 patients (37%) had SC disease at RP. All preoperative variables (ie, age and PSA at surgery, clinical stage, and biopsy Gleason sum) were independent predictors of SC PCa at RP (all p≤0.04). Patients with SC disease had significantly higher 10-yr BCR-free survival and CSS rates than patients without SC disease at RP (66% vs 47% and 98 vs 88%, respectively; all p<0.001). A nomogram including PSA, age, clinical stage, and biopsy Gleason sum demonstrated 72% accuracy in predicting SC PCa. This study is limited by its retrospective design and by the lack of an external validation of the nomogram. CONCLUSIONS Roughly 40% of patients with high-risk PCa have SC disease at final pathology. These patients showed excellent long-term outcomes when surgically treated, thus representing the ideal candidates for RP as the primary treatment for PCa. Prediction of such patients is possible using a nomogram based on routinely available clinical parameters.

Impact of Age and Comorbidities on Long-term Survival of Patients with High-risk Prostate Cancer Treated with Radical Prostatectomy: A Multi-institutional Competing-risks Analysis.

BACKGROUND Survival after surgical treatment using competing-risk analysis has been previously examined in patients with prostate cancer (PCa). However, the combined effect of age and comorbidities has not been assessed in patients with high-risk PCa who might have heterogeneous rates of competing mortality despite the presence of aggressive disease. OBJECTIVE To examine the risk of 10-yr cancer-specific mortality (CSM) and other-cause mortality (OCM) according to clinical and pathologic characteristics of patients treated with radical prostatectomy (RP) for high-risk PCa. DESIGN, SETTING, AND PARTICIPANTS Within a multi-institutional cohort, 3828 men treated with RP for high-risk PCa (defined as the presence of at least one of these risk factors: prostate-specific antigen >20 ng/ml, biopsy Gleason score 8-10, clinical stage ≥ T3) were identified. INTERVENTION All patients underwent RP and pelvic lymph node dissection. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS Competing-risk Poisson regression analyses were performed to simultaneously assess the 10-yr CSM and OCM rates after RP. The same analyses were also conducted after stratification of patients according to age at surgery, comorbidity status assessed by the Charlson Comorbidity Index (CCI), and number of risk factors (one vs two or more). RESULTS AND LIMITATIONS Overall, 229 patients (5.9%) died from PCa; 549 (14.3%) died from other causes. The 10-yr CSM and OCM rates ranged from 5.1% to 12.8% and from 4.3% to 37.4%, respectively. Age and CCI were the major determinants of OCM; their impact on CSM was minimal. OCM was the leading cause of death in all patient groups except in young men (≤ 59 yr) with no comorbidities, regardless of the number of risk factors (10-yr CSM and OCM 6.9-12.8% and 5.5-6.3%, respectively). The main limitation was the lack of patients managed conservatively. CONCLUSIONS Even in the context of high-risk PCa, long-term CSM after RP is modest and represents the leading cause of death only in young, healthy patients. Conversely, older and sicker patients with multiple risk factors are at the highest risk of dying from OCM while sharing very low CSM rates.

Survival in Patients with High-Risk Prostate Cancer Is Predicted by miR-221, Which Regulates Proliferation, Apoptosis, and Invasion of Prostate Cancer Cells by Inhibiting IRF2 and SOCS3

A lack of reliably informative biomarkers to distinguish indolent and lethal prostate cancer is one reason this disease is overtreated. miR-221 has been suggested as a biomarker in high-risk prostate cancer, but there is insufficient evidence of its potential utility. Here we report that miR-221 is an independent predictor for cancer-related death, extending and validating earlier findings. By mechanistic investigations we showed that miR-221 regulates cell growth, invasiveness, and apoptosis in prostate cancer at least partially via STAT1/STAT3-mediated activation of the JAK/STAT signaling pathway. miR-221 directly inhibits the expression of SOCS3 and IRF2, two oncogenes that negatively regulate this signaling pathway. miR-221 expression sensitized prostate cancer cells for IFN-γ-mediated growth inhibition. Our findings suggest that miR-221 offers a novel prognostic biomarker and therapeutic target in high-risk prostate cancer.