Biomedical subjects

Marcos Malumbres

Publications and source records attributed to Marcos Malumbres.

At least 19 recordsLinked to original sources

PubMed2007

Cell cycle kinases in cancer.

Cell division in mammalian cells is driven by protein kinases that regulate progression through the various phases of the cell cycle. Cyclin-dependent kinases (Cdks) regulate cell cycle commitment, DNA synthesis and the onset of mitosis. Kinases of the Aurora, Polo and Nek families participate in the centrosome cycle and modulate spindle function. Additional kinases such as Bub1, BubR1 and Mps1 regulate the spindle assembly checkpoint. It has been well established that misregulation of Cdks is one of the most frequent alterations in human cancer. Recent evidence indicates that mutations involving mitotic kinases are also linked to tumor development. These findings suggest novel strategies to use cell cycle kinases as targets for therapeutic intervention.

Aurora Kinases↗

PubMed2006

Cannabinoid receptors as novel targets for the treatment of melanoma.

Melanoma causes the greatest number of skin cancer-related deaths worldwide. Despite intensive research, prevention and early detection are the only effective measures against melanoma, so new therapeutic strategies are necessary for the management of this devastating disease. Here, we evaluated the efficacy of cannabinoid receptor agonists, a new family of potential antitumoral compounds, at skin melanoma. Human melanomas and melanoma cell lines express CB1 and CB2 cannabinoid receptors. Activation of these receptors decreased growth, proliferation, angiogenesis and metastasis, and increased apoptosis, of melanomas in mice. Cannabinoid antimelanoma activity was independent of the immune status of the animal, could be achieved without overt psychoactive effects and was selective for melanoma cells vs. normal melanocytes. Cannabinoid antiproliferative action on melanoma cells was due, at least in part, to cell cycle arrest at the G1-S transition via inhibition of the prosurvival protein Akt and hypophosphorylation of the pRb retinoblastoma protein tumor suppressor. These findings may contribute to the design of new chemotherapeutic strategies for the management of melanoma.

Animals↗

PubMed2006

Spontaneous and UV radiation-induced multiple metastatic melanomas in Cdk4R24C/R24C/TPras mice.

Human melanoma susceptibility is often characterized by germ-line inactivating CDKN2A (INK4A/ARF) mutations, or mutations that activate CDK4 by preventing its binding to and inhibition by INK4A. We have previously shown that a single neonatal UV radiation (UVR) dose delivered to mice that carry melanocyte-specific activation of Hras (TPras) increases melanoma penetrance from 0% to 57%. Here, we report that activated Cdk4 cooperates with activated Hras to enhance susceptibility to melanoma in mice. Whereas UVR treatment failed to induce melanomas in Cdk4(R24C/R24C) mice, it greatly increased the penetrance and decreased the age of onset of melanoma development in Cdk4(R24C/R24C)/TPras animals compared with TPras alone. This increased penetrance was dependent on the threshold of Cdk4 activation as Cdk4(R24C/+)/TPras animals did not show an increase in UVR-induced melanoma penetrance compared with TPras alone. In addition, Cdk4(R24C/R24C)/TPras mice invariably developed multiple lesions, which occurred rarely in TPras mice. These results indicate that germ-line defects abrogating the pRb pathway may enhance UVR-induced melanoma. TPras and Cdk4(R24C/R24C)/TPras tumors were comparable histopathologically but the latter were larger and more aggressive and cultured cells derived from such melanomas were also larger and had higher levels of nuclear atypia. Moreover, the melanomas in Cdk4(R24C/R24C)/TPras mice, but not in TPras mice, readily metastasized to regional lymph nodes. Thus, it seems that in the mouse, Hras activation initiates UVR-induced melanoma development whereas the cell cycle defect introduced by mutant Cdk4 contributes to tumor progression, producing more aggressive, metastatic tumors.

Animals↗

PubMed2006

Evaluation of genetic melanoma vaccines in cdk4-mutant mice provides evidence for immunological tolerance against authochthonous melanomas in the skin.

We evaluated the efficacy of a candidate melanoma vaccine approach in mice genetically prone to develop melanoma due to the introduction of an oncogenic mutation (R24C) in the germline sequence of the cyclin-dependent kinase 4 (cdk4), a protein critically involved in cell cycle regulation. Melanomas were induced in cdk4-mutant mice by chemical carcinogenesis and UVB irradiation. A genetic prime-boost strategy targeting the clinically relevant differentiation antigen tyrosinase-related protein 2 (TRP2) was performed which was able to stimulate a melanocyte-specific cellular immune response associated with localized autoimmune vitiligo-like depigmentation. However, significant destruction of carcinogen-induced autochthonous melanocytic neoplasms in the skin was not observed following immunization. We provide evidence that autochthonous melanomas expressed TRP2 but not the MHC molecule H2-Kb and are immunologically tolerated in the skin. Our results highlight the importance of assessing melanoma vaccines in genetic mouse models that more adequately represent the expected clinical situation in order to identify strategies, which eventually may be of benefit for melanoma patients.

Animals↗

PubMed2006

Preclinical models for cell cycle-targeted therapies.

Deregulation of the cell cycle machinery is frequently associated to tumor development in most cell types. Many of these tumor-associated alterations result in the abnormal activation of cyclin-dependent protein kinases (Cdks) involved in the G1/S transition. Recent results from the genetic analysis of cyclins and Cdks in mouse models have raised some questions regarding the relevance of these molecules in cell cycle-targeted strategies for cancer therapy. The comprehensive evaluation of these biochemical and genetic data seems to be a necessary given the relevance of these and other new cell cycle kinases as targets for therapeutic approaches in cancer.

Animals↗

PubMed2006

Therapeutic opportunities to control tumor cell cycles.

Tumor cell proliferation is frequently associated to genetic or epigenetic alterations in key cell cycle regulators. Most human tumors deregulate this pathway to sustain proliferation with independence of external mitogenic factors. In addition, the alteration of cell cycle proteins may confer genomic instability that results in additional mutations in these tumor cells. The frequent alteration of the cell cycle in tumor cells has launched the identification for critical cell cycle regulators as anticancer targets. The inhibition of some cell cycle kinases such as cyclin-dependent kinases (CDKs) or the Aurora and Polo mitotic kinases is currently under study in several preclinical and clinical trials. Similarly, the clinical success of microtubule poisons such as taxol has promoted new applied research in mitosis regulation. Recent investigations have suggested new targets of interest including additional kinases, phosphatases and other mitotic regulators such as microtubule motor proteins (kinesins). Current research in this area will undoubtedly result in new and improved targeted therapies for cancer treatment.

Animals↗

PubMed2006

Is Cyclin D1-CDK4 kinase a bona fide cancer target?

Previous studies have demonstrated that mice lacking Cyclin D1 were refractory to mammary tumor development induced by the c-neu/erbB-2 oncogene, the rodent ortholog of the HER-2 receptor frequently overexpressed in human breast carcinomas. Two new studies in this issue of Cancer Cell provide additional evidence on this issue. Knockin mice expressing a mutant form of Cyclin D1 that binds to Cdk4/6 but cannot activate their catalytic activity are resistant to c-neu/erbB-2 tumorigenesis in spite of undergoing normal epithelial cell expansion during pregnancy. Moreover, knockdown of Cdk4 in mammary tumor cells abrogates tumor formation. These observations provide new compelling evidence that inhibition of Cyclin D1-Cdk4/6 kinases might be beneficial for cancer therapy.

Animals↗

PubMed2006

Rapid growth of invasive metastatic melanoma in carcinogen-treated hepatocyte growth factor/scatter factor-transgenic mice carrying an oncogenic CDK4 mutation.

Currently, novel mouse models of melanoma are being generated that recapitulate the histopathology and molecular pathogenesis observed in human disease. Impaired cell-cycle control, which is a hallmark of both familial and sporadic melanoma, promotes slowly growing carcinogen-induced melanomas in the skin of mice carrying a mutated cyclin-dependent kinase 4 (CDK4(R24C)). Deregulated receptor tyrosine kinase signaling, which is another important feature of human melanoma, leads to spontaneous development of metastatic melanoma after a long latency period in mice overexpressing hepatocyte growth factor/scatter factor (HGF/SF mice). Here we report that treatment with 7,12-dimethylbenz[a]anthracene and 12-O-tetradecanoylphorbol-13-acetate induced metastatic melanomas in all HGF/SF mice on the C57BL/6 background, which histologically resemble human melanoma. Importantly, mutant CDK4 dramatically increased the number and the growth kinetics of carcinogen-induced primary melanomas in the skin and promoted the growth of spontaneous metastases in lymph nodes and lungs in all HGF/SF mice within the first 3 months of life. Apart from very few skin papillomas, we did not observe tumors of other histology in carcinogen-treated HGF/SF x CDK4(R24C) mice. This new experimental mouse model can now be exploited to study further the biology of melanoma and evaluate new treatment modalities.

Animals↗

PubMed2005

Mammalian cyclin-dependent kinases.

Cyclin-dependent kinases (Cdks) are the catalytic subunits of a family of mammalian heterodimeric serine/threonine kinases that have been implicated in the control of cell-cycle progression, transcription and neuronal function. Recent genetic evidence obtained with gene-targeted mice has shown that Cdk4 and Cdk6 are not needed for entry into the cell cycle after mitogenic stimuli and organogenesis; however, they are essential for the proliferation of some endocrine and hematopoietic cells. Cdk2 is also dispensable for the mitotic cell cycle. Indeed, mice without Cdk2 are normal except for their complete sterility: unexpectedly, Cdk2 is crucial for the first meiotic division of male and female germ cells. These findings have important implications both for our current understanding of the role of Cdks in regulating the mammalian cell cycle and for their potential use as therapeutic targets in cancer.

Animals↗

PubMed2005

Cooperation between Cdk4 and p27kip1 in tumor development: a preclinical model to evaluate cell cycle inhibitors with therapeutic activity.

Deregulation of the G1-S transition of the cell cycle is a common feature of human cancer. Tumor-associated alterations in this process frequently affect cyclin-dependent kinases (Cdk), their regulators (cyclins, INK4 inhibitors, or p27Kip1), and their substrates (retinoblastoma protein). Although these proteins are generally thought to act in a linear pathway, mutations in different components frequently cooperate in tumor development. Using gene-targeted mouse models, we report in this article that Cdk4 resistance to INK4 inhibitors, due to the Cdk4 R24C mutation, strongly cooperates with p27(Kip1) deficiency in tumor development. No such cooperation is observed between Cdk4 R24C and p18(INK4c) absence, suggesting that the only function of p18INK4c is inhibiting Cdk4 in this model. Cdk4(R/R) knock in mice, which express the Cdk4 R24C mutant protein, develop pituitary tumors with complete penetrance and short latency in a p27Kip1-/- or p27Kip1+/- background. We have investigated whether this tumor model could be useful to assess the therapeutic activity of cell cycle inhibitors. We show here that exposure to flavopiridol, a wide-spectrum Cdk inhibitor, significantly delays tumor progression and leads to tumor-free survival in a significant percentage of treated mice. These data suggest that genetically engineered tumor models involving key cell cycle regulators are a valuable tool to evaluate drugs with potential therapeutic benefit in human cancer.

Alleles↗

PubMed2005

Mouse p10, an alternative spliced form of p15INK4b, inhibits cell cycle progression and malignant transformation.

The INK4 family of proteins negatively regulates cell cycle progression at the G(1)-S transition by inhibiting cyclin-dependent kinases. Two of these cell cycle inhibitors, p16(INK4A) and p15(INK4B), have tumor suppressor activities and are inactivated in human cancer. Interestingly, both INK4 genes express alternative splicing variants. In addition to p16(INK4A), the INK4A locus encodes a splice variant, termed p12--specifically expressed in human pancreas--and ARF, a protein encoded by an alternative reading frame that acts as a tumor suppressor through the p53 pathway. Similarly, the human INK4B locus encodes the p15(INK4B) tumor suppressor and one alternatively spliced form, termed as p10. We show here that p10, which arises from the use of an alternative splice donor site within intron 1, is conserved in the mouse genome and is widely expressed in mouse tissues. Similarly to mouse p15(INK4B), p10 expression is also induced by oncogenic insults and transforming growth factor-beta treatment and acts as a cell cycle inhibitor. Importantly, we show that mouse p10 is able to induce cell cycle arrest in a p53-dependent manner. We also show that mouse p10 is able to inhibit foci formation and anchorage-independent growth in wild-type mouse embryonic fibroblasts, and that these antitransforming properties of mouse p10 are also p53-dependent. These results indicate that the INK4B locus, similarly to INK4A-ARF, harbors two different splicing variants that can be involved in the regulation of both the p53 and retinoblastoma pathways, the two major molecular pathways in tumor suppression.

Alternative Splicing↗

PubMed2005

Revisiting the "Cdk-centric" view of the mammalian cell cycle.

Since the early genetic studies in yeast, regulation of the cell cycle has been associated with the sequential activation of several proline-directed serine-threonine protein kinases by cyclins. From yeast to humans, the activity of these cyclin-dependent kinases (Cdks) have been thought to be essential for cell cycle regulation. Recent gene-targeted mouse models for different cyclins and Cdks have shown that members of these families show a certain level of redundancy and that specific complexes are not required for the mitotic cell cycle. However, the complexity of the Cdk-cyclin network and the promiscuity of their members makes it difficult to understand the relative contribution of these proteins to the mammalian cell division cycle. Compensatory roles by non-Cdk activities and Cdk-independent functions of cyclins are increasing the complexity of the current simplistic models. We still do not know whether at least one cyclin-dependent kinase activity is required for cell cycle progression in mammalian cells. Indeed, this is a relevant question for cancer therapy.

Animals↗

PubMed2005

Cdk2 is dispensable for cell cycle inhibition and tumor suppression mediated by p27(Kip1) and p21(Cip1).

p27(Kip1) and p21(Cip1) are thought to suppress tumor growth and prevent cell cycle progression by inhibiting Cdk2-cyclin E/A kinases. Since Cdk2 is dispensable for mitotic cell division, we analyzed the activity of these inhibitors in Cdk2-deficient cells. Ectopic expression of p27(Kip1) or p21(Cip1) efficiently inhibits cell cycle progression of Cdk2(-/-) fibroblasts. Loss of p27(Kip1) or p21(Cip1) confers similar proliferative advantages to Cdk2(+/+) and Cdk2(-/-) cells. Moreover, Cdk2 is dispensable for p21(Cip1)-induced cell cycle arrest after DNA damage. Finally, ablation of Cdk2 in p27(Kip1) null mice does not suppress their phenotypic defects, including development of pituitary tumors. These results indicate that Cdk2 is not an essential target for p27(Kip1) and p21(Cip1) in cell cycle inhibition and tumor suppression.

Animals↗

PubMed2005

Cdk4 promotes adipogenesis through PPARgamma activation.

Cell cycle regulators such as E2F1 and retinoblastoma (RB) play crucial roles in the control of adipogenesis, mostly by controlling the transition between preadipocyte proliferation and adipocyte differentiation. The serine-threonine kinase cyclin-dependent kinase 4 (cdk4) works in a complex with D-type cyclins to phosphorylate RB, mediating the entry of cells into the cell cycle in response to external stimuli. Because cdk4 is an upstream regulator of the E2F-RB pathway, we tested whether cdk4 was a target for new factors that regulate adipogenesis. Here we find that cdk4 inhibition impairs adipocyte differentiation and function. Disruption of cdk4 or activating mutations in cdk4 in primary mouse embryonic fibroblasts results in reduced and increased adipogenic potential, respectively, of these cells. We show that the effects of cdk4 are not limited to the control of differentiation; cdk4 also participates in adipocyte function through activation of PPARgamma.

3T3-L1 Cells↗

PubMed2004

Mammalian cells cycle without the D-type cyclin-dependent kinases Cdk4 and Cdk6.

Cdk4 and Cdk6 are thought to be essential for initiation of the cell cycle in response to mitogenic stimuli. Previous studies have shown that Cdk4 is dispensable for proliferation in most cell types, an observation attributed to a putative compensatory role by Cdk6. Cdk6-null mice are viable and develop normally although hematopoiesis is slightly impaired. Embryos defective for Cdk4 and Cdk6 die during the late stages of embryonic development due to severe anemia. However, these embryos display normal organogenesis and most cell types proliferate normally. In vitro, embryonic fibroblasts lacking Cdk4 and Cdk6 proliferate and become immortal upon serial passage. Moreover, quiescent Cdk4/Cdk6-null cells respond to serum stimulation and enter S phase with normal kinetics although with lower efficiency. These results indicate that D-type cyclin-dependent kinases are not essential for cell cycle entry and suggest the existence of alternative mechanisms to initiate cell proliferation upon mitogenic stimulation.

Animals↗

PubMed2004

The European dimension for the mouse genome mutagenesis program.

The European Mouse Mutagenesis Consortium is the European initiative contributing to the international effort on functional annotation of the mouse genome. Its objectives are to establish and integrate mutagenesis platforms, gene expression resources, phenotyping units, storage and distribution centers and bioinformatics resources. The combined efforts will accelerate our understanding of gene function and of human health and disease.

Animals↗

PubMed2003

Hypermethylation of the Ink4b locus in murine myeloid leukemia and increased susceptibility to leukemia in p15(Ink4b)-deficient mice.

The Ink4b gene (Cdkn2b) encodes p15(Ink4b), a cyclin-dependent kinase inhibitor. It has been implicated in playing a role in the development of acute myeloid leukemia (AML) in man, since it is hypermethylated with high frequency. We provide evidence that the gene is a tumor suppressor for myeloid leukemia in mice. The evidence is twofold: (1) retrovirus-induced myeloid leukemias of the myelomonocytic phenotype were found to have hypermethylation of the 5' CpG island of the Ink4b gene, and this could be correlated with reduced mRNA expression, as demonstrated by TaqMan real-time PCR. p15(Ink4b) mRNA expression in a leukemia cell line, with hypermethylation at the locus, was induced following treatment with 5-aza-2'-deoxycytidine. (2) Targeted deletion of one allele in mice by removal of exon 2 increases their susceptibility to retrovirus-induced myeloid leukemia. Mice deficient in both alleles were not more susceptible to myeloid disease than those deficient in one allele, raising the possibility that there are opposing forces related to the development of myeloid leukemia in Ink4b null mice.

Animals↗

PubMed2003

Cyclin-dependent kinase 2 is essential for meiosis but not for mitotic cell division in mice.

We targeted the locus encoding the cyclin-dependent kinase 2 (CDK2) by homologous recombination in mouse embryonic stem (ES) cells. Embryonic fibroblasts lacking CDK2 proliferate normally and become immortal after continuous passage in culture. Elimination of a conditional Cdk2 allele in immortal cells does not have a significant effect on proliferation. Cdk2-/- mice are viable and survive for up to two years, indicating that CDK2 is also dispensable for proliferation and survival of most cell types. But CDK2 is essential for completion of prophase I during meiotic cell division in male and female germ cells, an unforeseen role for this cell cycle kinase.

Animals↗