Runx1 promotes B-cell survival and lymphoma development.

Runx1 is essential for the homeostatic control of normal hematopoiesis and is required for lymphoid development. Translocations or point mutations that result in RUNX1 loss or disrupted function predispose to leukemia but data derived from model systems suggests that Runx genes can also be pro-oncogenic. Here we investigate the effects of enforced Runx1 expression in lymphoid lineages both in vivo and in vitro and show that transgene expression enhanced cell survival in the thymus and bone marrow but strongly inhibited the expansion of hematopoietic and B cell progenitors in vitro. Despite this, modestly enhanced levels of Runx1 accelerated Myc-induced lymphomagenesis in both the B cell and T cell lineages. Together these data provide formal proof that wild type Runx1 can promote oncogenesis in lymphoid tissues and that, in addition to loss of function, gain of function may have an aetiological role in leukemia.

Insertional mutagenesis reveals progression genes and checkpoints in MYC/Runx2 lymphomas.

In this study, we have exploited the power of insertional mutagenesis to elucidate tumor progression pathways in mice carrying two oncogenes (MYC/Runx2) that collaborate to drive early lymphoma development. Neonatal infection of these mice with Moloney murine leukemia virus resulted in accelerated tumor onset with associated increases in clonal complexity and lymphoid dissemination. Large-scale analysis of retroviral integration sites in these tumors revealed a profound bias towards a narrow range of target genes, including Jdp2 (Jundm2), D cyclin, and Pim family genes. Remarkably, direct PCR analysis of integration hotspots revealed that every progressing tumor consisted of multiple clones harboring hits at these loci, giving access to large numbers of independent insertion events and uncovering the contrasting mutagenic mechanisms operating at each target gene. Direct PCR analysis showed that high-frequency targeting occurs only in the tumor environment in vivo and is specific for the progression gene set. These results indicate that early lymphomas in MYC/Runx2 mice remain dependent on exogenous growth signals, and that progression can be achieved by constitutive activation of pathways converging on a cell cycle checkpoint that acts as the major rate-limiting step for lymphoma outgrowth.

Requirement for Rac1 in a K-ras induced lung cancer in the mouse.

Given the prevalence of Ras mutations in human cancer, it is critical to understand the effector pathways downstream of oncogenic Ras leading to transformation. To directly assess the requirement for Rac1 in K-ras-induced tumorigenesis, we employed a model of lung cancer in which an oncogenic allele of K-ras could be activated by Cre-mediated recombination in the presence or absence of conditional deletion of Rac1. We show that Rac1 function is required for tumorigenesis in this model. Furthermore, although Rac1 deletion alone was compatible with cell viability and proliferation, when combined with K-ras activation in primary epithelial cells, loss of Rac1 caused a profound reduction in proliferation. These data show a specific requirement for Rac1 function in cells expressing oncogenic K-ras.

Runx2 and MYC collaborate in lymphoma development by suppressing apoptotic and growth arrest pathways in vivo.

Members of the Runx and MYC families have been implicated as collaborating oncogenes. The mechanism of this potent collaboration is elucidated in this study of Runx2/MYC mice. As shown previously, ectopic expression of Runx2 in the thymus leads to a preneoplastic state defined by an accumulation of cells with an immature phenotype and a low proliferative rate. We now show that c-MYC overexpression is sufficient to rescue proliferation and to release the differentiation block imposed by Runx2. Analysis of Runx2-expressing lymphomas reveals a consistently low rate of apoptosis, in contrast to lymphomas of MYC mice which are often highly apoptotic. The low apoptosis phenotype is dominant in Runx2/MYC tumors, indicating that Runx2 confers a potent survival advantage to MYC-expressing tumor cells. The role of the p53 pathway in Runx2/MYC tumors was explored on a p53 heterozygote background. Surprisingly, functional p53 was retained in vivo, even after transplantation, whereas explanted tumor cells displayed rapid allele loss in vitro. Our results show that Runx2 and MYC overcome distinct "fail-safe" responses and that their selection as collaborating genes is due to their ability to neutralize each other's negative growth effect. Furthermore, the Runx2/MYC combination overcomes the requirement for genetic inactivation of the p53 pathway in vivo.

The current status of allied dental faculty: a survey report.

Allied dental program directors have expressed increasing concerns about possible current and future shortages of allied dental educators. As a result, the ADEA Board of Directors created a task force to investigate the current status of allied dental faculty, including the degree of cultural diversity, and to identify whether current and/or potential future shortages of educators exist. A survey was sent to all accredited allied dental program directors. Results indicated that a current faculty shortage exists for dental assisting and dental hygiene programs, with a projected greater future shortage for all allied dental education disciplines, primarily as a result of retirement of current faculty members. The data collected also revealed a lack of diversity in allied dental faculties, especially in dental hygiene and dental assisting programs. Recommendations for action steps included investigating: 1) the use of technology to provide the faculty expertise necessary to allow more affordable quality education in almost any location and to maximize available resources; 2) alternative ways to reward faculty; 3) loan forgiveness as an incentive for exemplary graduates to pursue educational career goals; 4) an ongoing database to monitor the status of allied dental educators; and 5) best practices in higher education to attract a more diverse student body and faculty in terms of gender, ethnicity, and race.

Notch1 is required for Kras-induced lung adenocarcinoma and controls tumor cell survival via p53.

The Notch pathway has been implicated in a number of malignancies with different roles that are cell- and tissue-type dependent. Notch1 is a putative oncogene in non-small cell lung cancer (NSCLC) and activation of the pathway represents a negative prognostic factor. To establish the role of Notch1 in lung adenocarcinoma, we directly assessed its requirement in Kras-induced tumorigenesis in vivo using an autochthonous model of lung adenocarcinoma with concomitant expression of oncogenic Kras and deletion of Notch1. We found that Notch1 function is required for tumor initiation via suppression of p53-mediated apoptosis through the regulation of p53 stability. These findings implicate Notch1 as a critical effector in Kras-driven lung adenocarcinoma and as a regulator of p53 at a posttranslational level. Moreover, our study provides new insights to explain, at a molecular level, the correlation between Notch1 activity and poor prognosis in patients with NSCLC carrying wild-type p53. This information is critical for design and implementation of new therapeutic strategies in this cohort of patients representing 50% of NSCLC cases.

A survey of dental hygiene program directors: summary findings and conclusions.

To assist the ADEA Council of Allied Dental Program Directors in focusing future goals and actions, an online survey was developed and administered to the directors of the 300 Commission on Dental Accreditation (CODA)-accredited U.S. dental hygiene programs in November 2008. The survey solicited directors' opinions about certain contemporary dental hygiene issues such as entry-level education, the use of articulation agreements, the advanced dental hygiene practitioner (ADHP) model proposed by the American Dental Hygienists' Association, and accreditation. Over three-quarters of survey respondents indicated it is "important" or "somewhat important" to advance the entry-level educational requirements for dental hygiene practice to the baccalaureate level. Educational setting (four-year versus two-year) was a significant determinant in whether a respondent thought a baccalaureate degree should result from a dental hygiene educational program. Fifty-six percent of respondents' programs either have or are in the process of developing articulation agreements with other institutions. Seventy percent of all respondents felt it was important to support advancing the ADHP model. Over 60 percent of respondents noted the importance of developing competencies for degree completion and graduate programs, and 42 percent of respondents indicated that it was important to have a separate accreditation process for graduate-level programs. Conclusions suggest advancing entry-level education for dental hygiene is desired if it can maintain a role for both four-year and two-year institutions.

Notch1 functions as a tumor suppressor in a model of K-ras-induced pancreatic ductal adenocarcinoma.

K-ras is the most commonly mutated oncogene in pancreatic cancer and its activation in murine models is sufficient to recapitulate the spectrum of lesions seen in human pancreatic ductal adenocarcinoma (PDAC). Recent studies suggest that Notch receptor signaling becomes reactivated in a subset of PDACs, leading to the hypothesis that Notch1 functions as an oncogene in this setting. To determine whether Notch1 is required for K-ras-induced tumorigenesis, we used a mouse model in which an oncogenic allele of K-ras is activated and Notch1 is deleted simultaneously in the pancreas. Unexpectedly, the loss of Notch1 in this model resulted in increased tumor incidence and progression, implying that Notch1 can function as a tumor suppressor gene in PDAC.

Runx2 disruption promotes immortalization and confers resistance to oncogene-induced senescence in primary murine fibroblasts.

The Runx genes play paradoxical roles in cancer where they can function either as dominant oncogenes or tumor suppressors according to context. We now show that the ability to induce premature senescence in primary murine embryonic fibroblasts (MEF) is a common feature of all three Runx genes. However, ectopic Runx-induced senescence contrasts with Ras oncogene-induced senescence, as it occurs directly and lacks the hallmarks of proliferative stress. Moreover, a fundamental role for Runx function in the senescence program is indicated by the effects of Runx2 disruption, which renders MEFs prone to spontaneous immortalization and confers an early growth advantage that is resistant to stress-induced growth arrest. Runx2(-/-) cells are refractory to H-Ras(V12)-induced premature senescence, despite the activation of a cascade of growth inhibitors and senescence markers, and are permissive for oncogenic transformation. The aberrant behavior of Runx2(-/-) cells is associated with signaling defects and elevated expression of S-G(2)-M cyclins and their associated cyclin dependent kinase activities that may override the effects of growth inhibitory signals. Coupling of stress responses to the cell cycle represents a novel facet of Runx tumor suppressor function and provides a rationale for the lineage-specific effects of loss of Runx function in cancer.

A vector expressing feline mature IL-18 fused to IL-1beta antagonist protein signal sequence is an effective adjuvant to a DNA vaccine for feline leukaemia virus.

DNA vaccination using vectors expressing the gag/pol and env genes of feline leukaemia virus (FeLV) and plasmids encoding feline interleukin-12 (IL-12) and IL-18 completely protected cats from viraemia following challenge [Hanlon L, Argyle D, Bain D, Nicolson L, Dunham S, Golder MC, et al. Feline leukaemia virus DNA vaccine efficacy is enhanced by coadministration with interleukin-12 (IL-12) and IL-18 expression vectors. J Virol 2001;75:8424-33]. However, the relative contribution of each cytokine gene towards protection is unknown. This study aimed to resolve this issue. IL-12 and IL-18 constructs were modified to ensure effective expression, and bioactivity was demonstrated using specific assays. Kittens were immunised intramuscularly with FeLV DNA and various cytokine constructs. Together with control kittens, these were challenged oronasally with FeLV and monitored for 15 weeks. All six kittens given FeLV, IL-12 and IL-18 were protected from the establishment of persistent viraemia and four from latent infection. Of six kittens immunised with FeLV DNA and IL-18, all were protected from viraemia and five from latent infection. In contrast, three of five kittens given FeLV DNA and IL-12 became persistently viraemic. Therefore, the adjuvant effect on the FeLV DNA vaccine appears to reside in the expression of IL-18.

The Runx genes as dominant oncogenes.

We have shown previously that Runx2 is a frequent target (approximately equal to 30%) for proviral insertion in murine leukemia virus (MLV) induced T cell tumors in CD2-MYC transgenic mice. Further investigation of a large panel of these tumors revealed that a small number also contain insertions at either Runx3 or Runx1. None of the tumors contained insertions at more than one family member, but in each case proviral insertion was associated with a high level of expression from the upstream (P1) promoter of the respective target gene. Moreover, we confirmed that transcriptional activation of Runx1 does not affect the integrity of the coding sequence, as previously observed for Runx2. These observations suggest that the three Runx genes act as functionally redundant oncogenes in T-cell lymphoma development. To explore the oncogenic potential of Runx2 further we created transgenic mice that over-express this gene in the T cell compartment. These CD2-Runx2 animals show a preneoplastic enlargement of the CD8 immature single positive (ISP) thymocyte pool and develop lymphomas at a low incidence. Although the CD8 ISP population is greatly increased, unlike their wild type counterparts these cells are largely non-cycling. Co-expression of c-MYC in this lineage accentuates the CD8 ISP skew and induces rapid tumor development, confirming the potent synergy that exists between these two oncogenes. Experiments designed to understand the nature of the observed synergy are ongoing and are based on the hypothesis that Runx2 may exert a survival effect in c-MYC expressing tumors in vivo while c-MYC may rescue cells from the antiproliferative effects of Runx2. The oncogenic potential of Runx1 is also being assessed using primary murine embryonic fibroblasts (MEFs). These studies have revealed that while Runx1 exerts a growth suppressive effect in wild type cells a growth promoting effect is seen in the absence of p53, suggesting that the Runx genes may harbor latent oncogene-like properties.

Protection against feline immunodeficiency virus using replication defective proviral DNA vaccines with feline interleukin-12 and -18.

A molecular clone of the Glasgow-8 isolate of FIV (FIVGL8) was rendered replication defective by an in-frame deletion in either reverse transcriptase (deltaRT) or integrase (deltaIN) genes for use as DNA vaccines. To test the ability of these multi-gene vaccines to protect against two feline immunodeficiency virus (FIV) isolates of differing virulence, cats were immunized using either DNA vaccine alone or co-administered with interleukin-12 (IL-12) and/or interleukin-18 (IL-18) cytokine DNA. Animals were challenged sequentially with FIV-Petaluma (FIVPET) an FIV isolate of relatively low virulence and subsequently with the more virulent FIVGL8. A proportion of vaccinates (5/18 deltaIN and 2/12 deltaRT) were protected against primary challenge with FIV(PET). Five of the vaccinated-protected cats were re-challenged with FIV(PET); four (all deltaIN) remained free of viraemia whilst all naive controls became viraemic. Following subsequent challenge with the more virulent FIVGL8 these four vaccinated-protected animals all became viraemic but showed lower proviral loads than naive cats. This study suggests that while our current DNA vaccines may not produce sterilizing immunity against more virulent isolates of FIV, they may nevertheless significantly reduce the impact of infection.