A self-renewal program controls the expansion of genetically unstable cancer stem cells in pluripotent stem cell-derived tumors

Autophagy in glioma cells: An identity crisis with a clinical perspective

Over the last decade, autophagy has emerged as one of the critical cellular systems that control homeostasis. Besides management of normal homeostatic processes, autophagy can also be induced by tissue damage stress or by rapidly progressing tumors. During tumor progression, autophagy mediates a cellular reaction to the changes inside and outside of cells, which leads to tumor adaptation. Even though the regulation of autophagy seems universal and is a well-described process, its dysregulation and role in glioma progression remain an important topic of investigation. In this review, we summarize recent evidence of autophagy regulation in brain tumor tissues and possible interconnection between signaling pathways that govern cellular responses. This perspective may help to assess the qualitative differences and various outcomes in response to autophagy stimulation.

Developmental Exposure to Endocrine Disruptors Expands Murine Myometrial Stem Cell Compartment as a Prerequisite to Leiomyoma Tumorigenesis

Despite the high prevalence and major negative impact of uterine fibroids (UFs) on women's health, their pathogenesis remains largely unknown. While tumor-initiating cells have been previously isolated from UFs, the cell of origin for these tumors in normal myometrium has not been identified. We isolated cells with Stro1/CD44 surface markers from normal myometrium expressing stem cell markers Oct-4/c-kit/nanog that exhibited the properties of myometrial stem/progenitor-like cells (MSCs). Using a murine model for UFs, we showed that the cervix was a hypoxic "niche" and primary site (96%) for fibroid development in these animals. The pool size of these MSCs also responded to environmental cues, contracting with age and expanding in response to developmental environmental exposures that promote fibroid development. Translating these findings to women, the number of MSCs in unaffected human myometrium correlated with risk for developing UFs. Caucasian (CC) women with fibroids had increased numbers of MSCs relative to CC women without fibroids, and African-American (AA) women at highest risk for these tumors had the highest number of MSCs: AA-with fibroids > CC-with fibroids > AA-without fibroids > CC-without fibroids. These data identify Stro1⁺ /CD44⁺ MSCs as MSC/progenitor cell for UFs, and a target for ethnic and environmental factors that increase UF risk. Stem Cells 2017;35:666-678.

PGC Reversion to Pluripotency Involves Erasure of DNA Methylation from Imprinting Control Centers followed by Locus-Specific Re-methylation

Primordial germ cells (PGCs) are fate restricted to differentiate into gametes in vivo. However, when removed from their embryonic niche, PGCs undergo reversion to pluripotent embryonic germ cells (EGCs) in vitro. One of the major differences between EGCs and embryonic stem cells (ESCs) is variable methylation at imprinting control centers (ICCs), a phenomenon that is poorly understood. Here we show that reverting PGCs to EGCs involved stable ICC methylation erasure at Snrpn, Igf2r, and Kcnqot1. In contrast, the H19/Igf2 ICC undergoes erasure followed by de novo re-methylation. PGCs differentiated in vitro from ESCs completed Snrpn ICC erasure. However, the hypomethylated state is highly unstable. We also discovered that when the H19/Igf2 ICC was abnormally hypermethylated in ESCs, this is not erased in PGCs differentiated from ESCs. Therefore, launching PGC differentiation from ESC lines with appropriately methylated ICCs is critical to the generation of germline cells that recapitulate endogenous ICC erasure.

Establishment of a highly metastatic model with a newly isolated lung adenocarcinoma cell line

Lung cancer is the leading cause of malignancy-related death worldwide, and metastasis always results in a poor prognosis. However, therapeutic progress is hampered by a deficiency of appropriate pre-clinical metastatic models. To bridge this experimental gap, we developed an in vivo metastatic model via subcutaneous (s.c.) injection. The original cell line (XL-2) adopted in this model was newly isolated from the ascites of a patient with extensive metastases of lung adenocarcinoma, thereby avoiding any alteration of its initial molecular biology features from artificial serial cultivation. After comprehensive phenotypical and histological analysis, it was identified as a lung adenocarcinoma cell line. Additionally, the drug test showed that XL-2 cell line was sensitive to docetaxel, and resistant to doxorubicin, indicating it might serve as a cell line model of drug resistance for identifying mechanisms of tumors resistant to doxorubicin. Through this s.c. model, we further obtained a highly metastatic cell line (designated XL-2sci). The metastatic rate of mice in XL-2 group was 3/10, in contrast to the rate of 9/10 in XL-2sci group. Optical imaging, micro-computed tomography (micro-CT) scanning and Transwell assays were further applied to identify the enhanced metastatic capacity of Xl-2sci cells both in vivo and in vitro. Compared with XL-2 cells, ITRAQ labeled proteomics profiling study showed that some tumor metastasis-associated proteins were upregulated in XL-2sci cells, which also indicated the reliability of our model. Proliferation ability of XL-2 and XL-2sci were also evaluated. Results showed that highly metastatic XL-2sci possessed a decreased proliferation capacity versus XL-2, which demonstrated that its increased metastatic activity was not facilitated by a faster growth rate. In conclusion, we successfully developed an in vivo metastatic model using a newly established lung adenocarcinoma cell line, which will be beneficial to further investigations of lung cancer metastasis and to the development of anti-metastasis drugs.

CD44, Hyaluronan, the Hematopoietic Stem Cell, and Leukemia-Initiating Cells

CD44 is an adhesion molecule that varies in size due to glycosylation and insertion of so-called variant exon products. The CD44 standard isoform (CD44s) is highly expressed in many cells and most abundantly in cells of the hematopoietic system, whereas expression of CD44 variant isoforms (CD44v) is more restricted. CD44s and CD44v are known as stem cell markers, first described for hematopoietic stem cells and later on confirmed for cancer- and leukemia-initiating cells. Importantly, both abundantly expressed CD44s as well as CD44v actively contribute to the maintenance of stem cell features, like generating and embedding in a niche, homing into the niche, maintenance of quiescence, and relative apoptosis resistance. This is surprising, as CD44 is not a master stem cell gene. I here will discuss that the functional contribution of CD44 relies on its particular communication skills with neighboring molecules, adjacent cells and, last not least, the surrounding matrix. In fact, it is the interaction of the hyaluronan receptor CD44 with its prime ligand, which strongly assists stem cells to fulfill their special and demanding tasks. Recent fundamental progress in support of this “old” hypothesis, which may soon pave the way for most promising new therapeutics, is presented for both hematopoietic stem cell and leukemia-initiating cell. The contribution of CD44 to the generation of a stem cell niche, to homing of stem cells in their niche, to stem cell quiescence and apoptosis resistance will be in focus.

Stearoyl-CoA desaturase-1 is a key factor for lung cancer-initiating cells

In recent years, studies of cancer development and recurrence have been influenced by the cancer stem cells (CSCs)/cancer-initiating cells (CICs) hypothesis. According to this, cancer is sustained by highly positioned, chemoresistant cells with extensive capacity of self renewal, which are responsible for disease relapse after chemotherapy. Growth of cancer cells as three-dimensional non-adherent spheroids is regarded as a useful methodology to enrich for cells endowed with CSC-like features. We have recently reported that cell cultures derived from malignant pleural effusions (MPEs) of patients affected by adenocarcinoma of the lung are able to efficiently form spheroids in non-adherent conditions supplemented with growth factors. By expression profiling, we were able to identify a set of genes whose expression is significantly upregulated in lung tumor spheroids versus adherent cultures. One of the most strongly upregulated gene was stearoyl-CoA desaturase (SCD1), the main enzyme responsible for the conversion of saturated into monounsaturated fatty acids. In the present study, we show both by RNA interference and through the use of a small molecule inhibitor that SCD1 is required for lung cancer spheroids propagation both in stable cell lines and in MPE-derived primary tumor cultures. Morphological examination and image analysis of the tumor spheroids formed in the presence of SCD1 inhibitors showed a different pattern of growth characterized by irregular cell aggregates. Electron microscopy revealed that the treated spheroids displayed several features of cellular damage and immunofluorescence analysis on optical serial sections showed apoptotic cells positive for the M30 marker, most of them positive also for the stemness marker ALDH1A1, thus suggesting that the SCD1 inhibitor is selectively killing cells with stem-like properties. Furthermore, SCD1-inhibited lung cancer cells were strongly impaired in their in vivo tumorigenicity and ALDH1A1 expression. These results suggest that SCD1 is a critical target in lung cancer tumor-initiating cells.

Cancer Stem Cells: A Review of Potential Clinical Applications

Context.—Cancer stem cells (CSCs) comprise a minor cell population in a tumor; however, they possess self-renewal capacity and are responsible for tumor recurrence and the emerging issue of tumor resistance. Despite recent advances in the study of pathogenesis and mechanisms of CSC-mediated disease recurrence and multidrug resistance, many questions remain unanswered.

Objectives.—To provide an overview of CSC theory and to describe major methods of CSC detection and isolation, with the emphasis on those techniques that are potentially relevant in clinical laboratory practice. Particular attention is given to CSC markers, such as cancer testis antigens, which could become promising targets in the development of immunotherapy in settings of minimal residual disease.

Data Sources.—The review is based on analysis of peer-reviewed literature cited in PubMed, as well as preliminary results of studies conducted in our laboratory.

Conclusions.—Despite a lack of consensus in the scientific community on research methodology, CSCs have demonstrated significant potential as therapeutic targets in the treatment of cancer. Further research of CSC biology and markers will eventually lead to the development of novel therapeutic approaches for targeting these cells to treat resistant and recurrent tumors and minimal residual disease.

Establishment of a human colorectal cancer cell line P6C with stem cell properties and resistance to chemotherapeutic drugs

AIM

Cancer stem cells have the capacity to initiate and sustain tumor growth. In this study, we established a CD44(+) colorectal cancer stem cell line with particular emphasis on its self-renewal capacity, enhanced tumor initiation and drug resistance.

METHODS

Fresh colon cancer and paired normal colon tissues were collected from 13 patients who had not received chemotherapy or radiotherapy prior to surgery. Among the 6 single-cell derived clones, only the P6C cell line was cultured for more than 20 passages in serial culture and formed holoclones with high efficiency, and then the stemness gene expression, colony formation, tumorigenicity and drug sensitivities of the P6C cell line were examined.

RESULTS

Stemness proteins, including c-Myc, Oct3/4, Nanog, Lgr5, and SOX2, were highly expressed in the P6C cell line. Oct3/4-positive P6C cells mostly generated holoclones through symmetric division, while a small number of P6C cells generated meroclones through asymmetric division. P6C cells stably expressed CD44 and possessed a high capacity to form tumor spheres. A single cell-derived sphere was capable of generating xenograft tumors in nude mice. Compared to SW480 and HCT116 colorectal cancer cells, P6C cells were highly resistant to Camptothecin and 5-fluorouracil, the commonly used chemotherapeutic agents to treat colorectal cancers.

CONCLUSION

We established a colorectal cancer stem cell line P6C with a high tumorigenic capacity and the characteristics of normal stem cells. It will benefit the mechanistic studies on cancer stem cells and the development of drugs that specifically target the cancer stem cells.

Exploring the cancer stem cell phenotype with high-throughput screening applications

Several human cancer types consist of diverse cell populations that can differ in their tumor-driving potential. One breakthrough has been the identification of poorly differentiated tumor cells, herein termed cancer stem cells (CSCs). CSCs have been shown to initiate tumors in different model systems and have been implicated in cancer resistance to conventional therapies. The clinical relevance of CSCs has been increasingly recognized, and recent progress in their enrichment and characterization has paved the way for exploring CSC biology with high-throughput screening technologies. This article focuses on functional chemical and RNAi screens that have led to the identification of factors that control the CSC phenotype. Different experimental strategies, current challenges and perspectives in CSC drug discovery are discussed.

Centrosome loss or amplification does not dramatically perturb global gene expression in Drosophila

Centrosome defects are a common feature of many cancers, and they can predispose fly brain cells to form tumours. In flies, centrosome defects perturb the asymmetric division of the neural stem cells, but it is unclear how this might lead to malignant transformation. One possibility is that centrosome defects might also perturb cellular homeostasis: for example, stress pathways are often activated in response to centrosome defects in cultured cells, and stress contributes to tumourigenesis in some fly models. Here we attempt to assess whether centrosome loss or centrosome amplification perturbs cell physiology in vivo by profiling the global transcriptome of Drosophila larval brains and imaginal discs that either lack centrosomes or have too many centrosomes. Surprisingly, we find that centrosome loss or amplification leads to few changes in the transcriptional profile of these cells, indicating that centrosome defects are surprisingly well tolerated by these cells. These observations indicate that centrosome defects can predispose fly brain cells to form tumours without, at least initially, dramatically altering their physiology.

Cdk2ap2 is a novel regulator for self-renewal of murine embryonic stem cells

In this study we present data to support the role for Cdk2ap2 in regulating self-renewal of mouse embryonic stem cells (mESCs) under permissive conditions, and cell survival during differentiation of the mESCs into terminally differentiated cell types. To understand the function of Cdk2ap2 during early development, we generated mESCs with homozygous disruption of the endogenous Cdk2ap2 locus (Cdk2ap2(tr/tr)). The Cdk2ap2(tr/tr) mESCs, when grown in a complete growth medium containing leukemia inhibitory factor (LIF), showed an early differentiation phenotype characterized by flattened colonies and a distinct intercellular boundary. We also observed downregulation of Nanog and upregulation in markers of mesoderm and endoderm differentiation, including Brachyury (T), Afp, and S100a, when compared to Wt mESCs. Cdk2ap2(tr/tr) mESCs were able to form embryoid bodies (EBs); however, those EBs were unhealthy and had an increased level of apoptosis. Furthermore, Cdk2ap2(tr/tr) mESCs were unable to form teratomas in severe combined immunodeficiency (SCID) mice. Cdk2ap2 under normal conditions has a biphasic expression, suggesting regulatory roles in early-versus-late stem cell differentiation. These data begin to add to our understanding of how Cdk2ap2 may be involved in the regulation of self-renewal of stem cells during early embryogenesis.

Identification of specific pluripotent stem cell death--inducing small molecules by chemical screening

A potential application of embryonic and inducible pluripotent stem cells for the therapy of degenerative diseases involves pure somatic cells, free of tumorigenic undifferentiated embryonic and inducible pluripotent stem cells. In complex collections of chemicals with pharmacological potential we expect to find molecules able to induce specific pluripotent stem cell death, which could be used in some cell therapy settings to eliminate undifferentiated cells. Therefore, we have screened a chemical library of 1120 small chemicals to identify compounds that induce specifically apoptotic cell death in undifferentiated mouse embryonic stem cells (ESCs). Interestingly, three compounds currently used as clinically approved drugs, nortriptyline, benzethonium chloride and methylbenzethonium chloride, induced differential effects in cell viability in ESCs versus mouse embryonic fibroblasts (MEFs). Nortriptyline induced apoptotic cell death in MEFs but not in ESCs, whereas benzethonium and methylbenzethonium chloride showed the opposite effect. Nortriptyline, a tricyclic antidepressant, has also been described as a potent inhibitor of mitochondrial permeability transition, one of two major mechanisms involved in mitochondrial membrane permeabilization during apoptosis. Benzethonium chloride and methylbenzethonium chloride are quaternary ammonium salts used as antimicrobial agents with broad spectrum and have also been described as anticancer agents. A similar effect of benzethonium chloride was observed in human induced pluripotent stem cells (hiPSCs) when compared to both primary human skin fibroblasts and an established human fibroblast cell line. Human fibroblasts and hiPSCs were similarly resistant to nortriptyline, although with a different behavior. Our results indicate differential sensitivity of ESCs, hiPSCs and fibroblasts to certain chemical compounds, which might have important applications in the stem cell-based therapy by eliminating undifferentiated pluripotent stem cells from stem cell-derived somatic cells to prevent tumor formation after transplantation for therapy of degenerative diseases.

Phosphatase and tensin homolog regulates the pluripotent state and lineage fate choice in human embryonic stem cells

Understanding the intrinsic and extrinsic signals that regulate the molecular basis of the pluripotent state may improve our understanding of mammalian embryogenesis, different states of pluripotency, and our ability to tailor lineage differentiation. Although the role of the PI3K/Akt pathway in the self-renewal and maintenance of mESCs is well-established, the specific contribution of the pathway or of its negative regulator, PTEN, in the maintenance of the human pluripotent state is less understood. To explore the PI3K/AKT pathway in human embryonic stem cell (hESC) pluripotency and differentiation, we generated stable PTEN knockdown (KD) hESCs using short hairpin RNA. Similar to mESCs, we found that PTEN KD hESCs have increased self-renewal, cell survival, and proliferation over multiple passages compared to control cells. However, in contrast to mESCs, in vitro, PTEN KD hESCs differentiated inefficiently in directed differentiation assays, in part due to the continued maintenance of OCT4 and NANOG expression. In teratoma assays, PTEN KD hESCs generated tissues from the three germ layers, although with a bias toward neuroectoderm differentiation. These results demonstrate that PTEN is a key regulator of hESC growth and differentiation, and manipulation of this pathway may improve our ability to regulate and understand the pluripotent state.

Mitochondrial function controls proliferation and early differentiation potential of embryonic stem cells

Pluripotent stem cells hold significant promise in regenerative medicine due to their unlimited capacity for self-renewal and potential to differentiate into any cell type of the body. In this study, we demonstrate that proper mitochondrial function is essential for proliferation of undifferentiated ESCs. Attenuating mitochondrial function under self-renewing conditions makes these cells more glycolytic-dependent, and it is associated with an increase in the mRNA reserves of Nanog, Oct4, and Sox2. In contrast, attenuating mitochondrial function during the first 7 days of differentiation results in normal repression of Oct4, Nanog, and Sox2. However, differentiation potential is compromised as revealed by abnormal transcription of multiple Hox genes. Furthermore, under differentiating conditions in which mitochondrial function is attenuated, tumorigenic cells continue to persist. Our results, therefore establish the importance of normal mitochondrial function in ESC proliferation, regulating differentiation, and preventing the emergence of tumorigenic cells during the process of differentiation.

Spermatogonial stem cells, infertility and testicular cancer

The spermatogonial stem cells (SSCs) are responsible for the transmission of genetic information from an individual to the next generation. SSCs play critical roles in understanding the basic reproductive biology of gametes and treatments of human infertility. SSCs not only maintain normal spermatogenesis, but also sustain fertility by critically balancing both SSC self-renewal and differentiation. This self-renewal and differentiation in turn is tightly regulated by a combination of intrinsic gene expression within the SSC as well as the extrinsic gene signals from the niche. Increased SSCs self-renewal at the expense of differentiation result in germ cell tumours, on the other hand, higher differentiation at the expense of self-renewal can result in male sterility. Testicular germ cell cancers are the most frequent cancers among young men in industrialized countries. However, understanding the pathogenesis of testis cancer has been difficult because it is formed during foetal development. Recent studies suggest that SSCs can be reprogrammed to become embryonic stem (ES)-like cells to acquire pluripotency. In the present review, we summarize the recent developments in SSCs biology and role of SSC in testicular cancer. We believe that studying the biology of SSCs will not only provide better understanding of stem cell regulation in the testis, but eventually will also be a novel target for male infertility and testicular cancers.

Understanding tumor heterogeneity as functional compartments--superorganisms revisited

Compelling evidence broadens our understanding of tumors as highly heterogeneous populations derived from one common progenitor. In this review we portray various stages of tumorigenesis, tumor progression, self-seeding and metastasis in analogy to the superorganisms of insect societies to exemplify the highly complex architecture of a neoplasm as a system of functional "castes."

Accordingly, we propose a model in which clonal expansion and cumulative acquisition of genetic alterations produce tumor compartments each equipped with distinct traits and thus distinct functions that cooperate to establish clinically apparent tumors. This functional compartment model also suggests mechanisms for the self-construction of tumor stem cell niches. Thus, thinking of a tumor as a superorganism will provide systemic insight into its functional compartmentalization and may even have clinical implications.

CD44: can a cancer-initiating cell profit from an abundantly expressed molecule?

Can an abundantly expressed molecule be a reliable marker for the cancer-initiating cells (CICs; also known as cancer stem cells), which constitute the minority of cells within the mass of a tumour? CD44 has been implicated as a CIC marker in several malignancies of haematopoietic and epithelial origin. Is this a fortuitous coincidence owing to the widespread expression of the molecule or is CD44 expression advantageous as it fulfils some of the special properties that are displayed by CICs, such as self-renewal, niche preparation, epithelial-mesenchymal transition and resistance to apoptosis?

Combination therapy targeting both tumor-initiating and differentiated cell populations in prostate carcinoma

PURPOSE

The cancer stem cell hypothesis predicts that standard prostate cancer monotherapy eliminates bulk tumor cells but not a tumor-initiating cell population, eventually leading to relapse. Many studies have sought to determine the underlying differences between bulk tumor and cancer stem cells.

EXPERIMENTAL DESIGN

Our previous data suggest that the PTEN/PI3K/AKT pathway is critical for the in vitro maintenance of CD133(+)/CD44(+) prostate cancer progenitors and, consequently, that targeting PI3K signaling may be beneficial in treatment of prostate cancer.

RESULTS

Here, we show that inhibition of PI3K activity by the dual PI3K/mTOR inhibitor NVP-BEZ235 leads to a decrease in the population of CD133(+)/CD44(+) prostate cancer progenitor cells in vivo. Moreover, the combination of the PI3K/mTOR modulator NVP-BEZ235, which eliminates prostate cancer progenitor populations, and the chemotherapeutic drug Taxotere, which targets the bulk tumor, is significantly more effective in eradicating tumors in a prostate cancer xenograft model than monotherapy.

CONCLUSION

This combination treatment ultimately leads to the expansion of cancer progenitors with a PTEN E91D mutation, suggesting that the analysis of PTEN mutations could predict therapeutic response to the dual therapy.

Tumor-initiating cells and tumor vascularization

Tumor-initiating cells (TICs) with stem-like cell properties initiate and sustain progressive growth, resulting in a heterogeneous tumor mass. The survival and growth of tumors rely on the development of a vasculature to provide nutrients and oxygen. Crosstalk between TICs and vascularization may be one of the central players in the initiation, long-term maintenance, and progression of tumors. This review surveys current evidence concerning the crosstalk that occurs in tumor/stromal interactions, including genetic change, vascular niche, hypoxia, and dormancy of tumors. A better understanding of this crosstalk might help provide the basis for developing more effective therapeutic drug targets.

Loss of Pten causes tumor initiation following differentiation of murine pluripotent stem cells due to failed repression of Nanog

Pluripotent stem cells (PSCs) hold significant promise in regenerative medicine due to their unlimited capacity for self-renewal and potential to differentiate into every cell type in the body. One major barrier to the use of PSCs is their potential risk for tumor initiation following differentiation and transplantation in vivo. In the current study we sought to evaluate the role of the tumor suppressor Pten in murine PSC neoplastic progression. Using eight functional assays that have previously been used to indicate PSC adaptation or transformation, Pten null embryonic stem cells (ESCs) failed to rate as significant in five of them. Instead, our data demonstrate that the loss of Pten causes the emergence of a small number of aggressive, teratoma-initiating embryonic carcinoma cells (ECCs) during differentiation in vitro, while the remaining 90-95% of differentiated cells are non-tumorigenic. Furthermore, our data show that the mechanism by which Pten null ECCs emerge in vitro and cause tumors in vivo is through increased survival and self-renewal, due to failed repression of the transcription factor Nanog.

Aurora-a is essential for the tumorigenic capacity and chemoresistance of colorectal cancer stem cells

Colorectal cancer stem cells (CR-CSC) are responsible for the generation and maintenance of intestinal tumors and are highly resistant to conventional chemotherapeutic agents. Aurora-A, a serine-threonine kinase involved in mitosis regulation, plays multiple key functions in tumor initiation and progression. We found that Aurora-A is overexpressed in primary colorectal tumor cells, in the CR-CSC fraction, and in stem cell-derived differentiated cells, compared with normal colon tissue. Aurora-A expression was functionally linked to centrosome amplification in CR-CSC, as indicated by the decrease in cells with multiple centrosomes that followed Aurora-A silencing. Knockdown of Aurora-A resulted in growth inhibition of CR-CSC, alteration of cell cycle kinetics, and downregulation of the expression levels of antiapoptotic Bcl-2 family members, strongly sensitizing to chemotherapy-induced cell death. Moreover, Aurora-A silencing compromised the ability to form tumor xenografts in immunocompromised mice and reduced the migratory capacity of CR-CSC. Altogether, these results indicate that Aurora-A is essential for CR-CSC regeneration and resistance to cytotoxic stimuli and suggest that therapies directed against Aurora-A may effectively target the stem cell population in colorectal cancer.

A DNA methyltransferase inhibitor and all-trans retinoic acid reduce oral cavity carcinogenesis induced by the carcinogen 4-nitroquinoline 1-oxide

The transcriptional silencing of some cell cycle inhibitors and tumor suppressors, such as p16 and retinoic acid receptor beta(2), by DNA hypermethylation at CpG islands is commonly found in human oral squamous carcinoma cells. We examined the effects of the DNA methyltransferase inhibitor 5-Aza-2'-deoxycytidine (5-Aza; 0.25 mg/kg body weight), all-trans retinoic acid (RA; given at 100 microg/kg body weight and 1 mg/kg body weight), and the combination of 5-Aza and the low-dose RA on murine oral cavity carcinogenesis induced by the carcinogen 4-nitroquinoline 1-oxide (4-NQO) in a mouse model. All the drug treatments were done for 15 weeks after a 10-week 4-NQO treatment. Mice in all drug treatment groups showed decreases in the average numbers of neoplastic tongue lesions. The combination of 5-Aza and RA effectively attenuated tongue lesion severity. Although all drug treatments limited the increase in the percentage of proliferating cell nuclear antigen-positive cells and the decrease in the percentage of p16-positive cells caused by the 4-NQO treatment in mouse tongue epithelial regions without visible lesions and in the neoplastic tongue lesions, the combination of 5-Aza and RA was the most effective. Collectively, our results show that the combination of a DNA demethylating drug and RA has potential as a strategy to reduce oral cavity cancer in this 4-NQO model.

Targeted inactivation of p12, CDK2 associating protein 1, leads to early embryonic lethality

Targeted disruption of murine Cdk2ap1, an inhibitor of CDK2 function and hence G1/S transition, results in the embryonic lethality with a high penetration rate. Detailed timed pregnancy analysis of embryos showed that the lethality occurred between embryonic day 3.5 pc and 5.5 pc, a period of implantation and early development of implanted embryos. Two homozygous knockout mice that survived to term showed identical craniofacial defect, including a short snout and a round forehead. Examination of craniofacial morphology by measuring Snout Length (SL) vs. Face Width (FW) showed that the Cdk2ap1(+/-) mice were born with a reduced SL/FW ratio compared to the Cdk2ap1(+/+) and the reduction was more pronounced in Cdk2ap1(-/-) mice. A transgenic rescue of the lethality was attempted by crossing Cdk2ap1(+/-) animals with K14-Cdk2ap1 transgenic mice. Resulting Cdk2ap1(+/-:K14-Cdk2ap1) transgenic mice showed an improved incidence of full term animals (16.7% from 0.5%) on a Cdk2ap1(-/-) background. Transgenic expression of Cdk2ap1 in Cdk2ap1(-/-:K14-Cdk2ap1) animals restored SL/FW ratio to the level of Cdk2ap1(+/-:K14-Cdk2ap1) mice, but not to that of the Cdk2ap1(+/+:K14-Cdk2ap1) mice. Teratoma formation analysis using mESCs showed an abrogated in vivo pluripotency of Cdk2ap1(-/-) mESCs towards a restricted mesoderm lineage specification. This study demonstrates that Cdk2ap1 plays an essential role in the early stage of embryogenesis and has a potential role during craniofacial morphogenesis.