@article{macias_marval_de siervi_conti_senderowicz_rodriguez-puebla_2008, title={CDK2 activation in mouse epidermis induces keratinocyte proliferation but does not affect skin tumor development}, volume={173}, ISSN={["1525-2191"]}, DOI={10.2353/ajpath.2008.071124}, abstractNote={It has been widely assumed that elevated CDK2 kinase activity plays a contributory role in tumorigenesis. We have previously shown that mice overexpressing CDK4 under control of the keratin 5 promoter (K5CDK4 mice) develop epidermal hyperplasia and increased susceptibility to squamous cell carcinomas. In this model, CDK4 overexpression results in increased CDK2 activity associated with the noncatalytic function of CDK4, sequestration of p21(Cip1) and p27(Kip1). Furthermore, we have shown that ablation of Cdk2 reduces Ras-Cdk4 tumorigenesis, suggesting that increased CDK2 activity plays an important role in Ras-mediated tumorigenesis. To investigate this hypothesis, we generated two transgenic mouse models of elevated CDK2 kinase activity, K5Cdk2 and K5Cdk4(D158N) mice. The D158N mutation blocks CDK4 kinase activity without interfering with its binding capability. CDK2 activation via overexpression of CDK4(D158N), but not of CDK2, resulted in epidermal hyperplasia. We observed elevated levels of p21(Cip1) in K5Cdk2, but not in K5Cdk4(D158N), epidermis, suggesting that CDK2 overexpression elicits a p21(Cip1) response to maintain keratinocyte homeostasis. Surprisingly, we found that neither CDK2 overexpression nor the indirect activation of CDK2 enhanced skin tumor development. Thus, although the indirect activation of CDK2 is sufficient to induce keratinocyte hyperproliferation, activation of CDK2 alone does not induce malignant progression in Ras-mediated tumorigenesis.}, number={2}, journal={AMERICAN JOURNAL OF PATHOLOGY}, author={Macias, Everardo and Marval, Paula L. Miliani and De Siervi, Adriana and Conti, Claudio J. and Senderowicz, Adrian M. and Rodriguez-Puebla, Marcelo L.}, year={2008}, month={Aug}, pages={526–535} }
 @article{macias_marva_senderowicz_cullen_rodriguez-puebla_2008, title={Expression of CDK4 or CDK2 in mouse oral cavity is retained in adult pituitary with distinct effects on tumorigenesis}, volume={68}, ISSN={["0008-5472"]}, DOI={10.1158/0008-5472.CAN-07-2461}, abstractNote={Abstract
               The keratin 5 (K5) promoter drives transgenic expression to the basal cell layer of stratified epithelia. Surprisingly, analysis of K5CDK4 and K5CDK2 transgenic mouse embryos showed CDK4 and CDK2 expression not only in the expected tissues, but also in the adenohypophysis. This organ is derived from an upwards growth of the primitive oropharnyx, a K5-expressing tissue. We show that transgenic expression of CDKs in the embryonic oral ectoderm is specifically retained in undifferentiated cells from the pars intermedia of the adenohypophysis. Interestingly, we found that K5CDK4 mice show a decreased number of pituitary stem cells, even though CDK4 is not expressed in the stem cells but in transit-amplifying (TA)–like cells. Interestingly, CDK4-expressing cells, but not CDK2-expressing cells, strongly synergize with lack of p27Kip1 to generate pituitary carcinomas that appear with shortened latency and are drastically more aggressive than those arising in p27−/− mice. Thus, we show that deregulation of CDK expression in the primitive oral epithelium plays a unique function, providing a selective advantage that gives rise to transgene-positive TA-like pituitary cells. Furthermore, retention of CDK4 in these TA-like pituitary cells synergizes with loss of p27Kip1 to induce pituitary adenocarcinomas. This model suggests that forced expression of CDK4 sensitizes cells and synergizes with a second change resulting in tumor development. [Cancer Res 2008;68(1):162–71]}, number={1}, journal={CANCER RESEARCH}, author={Macias, Everardo and Marva, Paula L. Miliani and Senderowicz, Adrian and Cullen, John and Rodriguez-Puebla, Marcelo L.}, year={2008}, month={Jan}, pages={162–171} }
 @article{patil_lee_macias_lam_xu_jones_ho_rodriguez-puebla_chen_2009, title={Robe of Cyclin D1 as a Mediator of c-Met- and beta-Catenin-Induced Hepatocarcinogenesis}, volume={69}, ISSN={["1538-7445"]}, DOI={10.1158/0008-5472.CAN-08-2514}, abstractNote={Abstract
               Activation of c-Met signaling and β-catenin mutations are frequent genetic events observed in liver cancer development. Recently, we demonstrated that activated β-catenin can cooperate with c-Met to induce liver cancer formation in a mouse model. Cyclin D1 (CCND1) is an important cell cycle regulator that is considered to be a downstream target of β-catenin. To determine the importance of CCND1 as a mediator of c-Met– and β-catenin–induced hepatocarcinogenesis, we investigated the genetic interactions between CCND1, β-catenin, and c-Met in liver cancer development using mouse models. We coexpressed CCND1 with c-Met in mice and found CCND1 to cooperate with c-Met to promote liver cancer formation. Tumors induced by CCND1/c-Met had a longer latency period, formed at a lower frequency, and seemed to be more benign compared with those induced by β-catenin/c-Met. In addition, when activated β-catenin and c-Met were coinjected into CCND1-null mice, liver tumors developed despite the absence of CCND1. Intriguingly, we observed a moderate accelerated tumor growth and increased tumor malignancy in these CCND1-null mice. Molecular analysis showed an up-regulation of cyclin D2 (CCND2) expression in CCND1-null tumor samples, indicating that CCND2 may replace CCND1 in hepatic tumorigenesis. Together, our results suggest that CCND1 functions as a mediator of β-catenin during HCC pathogenesis, although other molecules may be required to fully propagate β-catenin signaling. Moreover, our data suggest that CCND1 expression is not essential for liver tumor development induced by c-Met and β-catenin. [Cancer Res 2009;69(1):253–61]}, number={1}, journal={CANCER RESEARCH}, author={Patil, Mohini A. and Lee, Susie A. and Macias, Everardo and Lam, Ernest T. and Xu, Chuanrui and Jones, Kirk D. and Ho, Coral and Rodriguez-Puebla, Marcelo and Chen, Xin}, year={2009}, month={Jan}, pages={253–261} }
 @article{macias_kim_marval_klein-szanto_rodriguez-puebla_2007, title={Cdk2 deficiency decreases ras/CDK4-dependent malignant progression, but not myc-induced tumorigenesis}, volume={67}, ISSN={["1538-7445"]}, DOI={10.1158/0008-5472.CAN-07-2119}, abstractNote={Abstract
               We have previously shown that forced expression of CDK4 in mouse skin (K5CDK4 mice) results in increased susceptibility to squamous cell carcinoma (SCC) development in a chemical carcinogenesis protocol. This protocol induces skin papilloma development, causing a selection of cells bearing activating Ha-ras mutations. We have also shown that myc-induced epidermal proliferation and oral tumorigenesis (K5Myc mice) depends on CDK4 expression. Biochemical analysis of K5CDK4 and K5Myc epidermis as well as skin tumors showed that keratinocyte proliferation is mediated by CDK4 sequestration of p27Kip1 and p21Cip1, and activation of CDK2. Here, we studied the role of CDK2 in epithelial tumorigenesis. In normal skin, loss of CDK2 rescues CDK4-induced, but not myc-induced epidermal hyperproliferation. Ablation of CDK2 in K5CDK4 mice results in decreased incidences and multiplicity of skin tumors as well as malignant progression to SCC. Histopathologic analysis showed that K5CDK4 tumors are drastically more aggressive than K5CDK4/CDK2−/− tumors. On the other hand, we show that CDK2 is dispensable for myc-induced tumorigenesis. In contrast to our previous report of K5Myc/CDK4−/−, K5Myc/CDK2−/− mice developed oral tumors with the same frequency as K5Myc mice. Overall, we have established that ras-induced tumors are more susceptible to CDK2 ablation than myc-induced tumors, suggesting that the efficacy of targeting CDK2 in tumor development and malignant progression is dependent on the oncogenic pathway involved. [Cancer Res 2007;67(20):9713–20]}, number={20}, journal={CANCER RESEARCH}, author={Macias, Everardo and Kim, Yongbaek and Marval, Paula L. Miliani and Klein-Szanto, Andres and Rodriguez-Puebla, Marcelo L.}, year={2007}, month={Oct}, pages={9713–9720} }
 @article{marval_macias_rounbehler_sicinski_kiyokawa_johnson_conti_rodriguez-puebla_2004, title={Lack of cyclin-dependent kinase 4 inhibits c-myc tumorigenic activities in epithelial tissues}, volume={24}, ISSN={["1098-5549"]}, DOI={10.1128/MCB.24.17.7538-7547.2004}, abstractNote={ABSTRACT The proto-oncogene c-myc encodes a transcription factor that is implicated in the regulation of cellular proliferation, differentiation, and apoptosis and that has also been found to be deregulated in several forms of human and experimental tumors. We have shown that forced expression of c-myc in epithelial tissues of transgenic mice (K5-Myc) resulted in keratinocyte hyperproliferation and the development of spontaneous tumors in the skin and oral cavity. Although a number of genes involved in cancer development are regulated by c-myc, the actual mechanisms leading to Myc-induced neoplasia are not known. Among the genes regulated by Myc is the cyclin-dependent kinase 4 (CDK4) gene. Interestingly, previous studies from our laboratory showed that the overexpression of CDK4 led to keratinocyte hyperproliferation, although no spontaneous tumor development was observed. Thus, we tested the hypothesis that CDK4 may be one of the critical downstream genes involved in Myc carcinogenesis. Our results showed that CDK4 inhibition in K5-Myc transgenic mice resulted in the complete inhibition of tumor development, suggesting that CDK4 is a critical mediator of tumor formation induced by deregulated Myc. Furthermore, a lack of CDK4 expression resulted in marked decreases in epidermal thickness and keratinocyte proliferation compared to the results obtained for K5-Myc littermates. Biochemical analysis of the K5-Myc epidermis showed that CDK4 mediates the proliferative activities of Myc by sequestering p21Cip1 and p27Kip1 and thereby indirectly activating CDK2 kinase activity. These results show that CDK4 mediates the proliferative and oncogenic activities of Myc in vivo through a mechanism that involves the sequestration of specific CDK inhibitors.}, number={17}, journal={MOLECULAR AND CELLULAR BIOLOGY}, author={Marval, PLM and Macias, E and Rounbehler, R and Sicinski, P and Kiyokawa, H and Johnson, DG and Conti, CJ and Rodriguez-Puebla, ML}, year={2004}, month={Sep}, pages={7538–7547} }
 @article{marval_macias_conti_rodriguez-puebla_2004, title={Enhanced malignant tumorigenesis in Cdk4 transgenic mice}, volume={23}, ISSN={["1476-5594"]}, DOI={10.1038/sj.onc.1207309}, abstractNote={In a previous study, we reported that overexpression of cyclin-dependent kinase-4 (CDK4) in mouse epidermis results in epidermal hyperplasia, hypertrophy and severe dermal fibrosis. In this study, we have investigated the susceptibility to skin tumor formation by forced expression of CDK4. Skin tumors from transgenic mice showed a dramatic increase in the rate of malignant progression to squamous cell carcinomas (SCC) in an initiation-promotion protocol. Histopathological analysis of papillomas from transgenic mice showed an elevated number of premalignant lesions characterized by dysplasia and marked atypia. Interestingly, transgenic mice also developed tumors in initiated but not promoted skin, demonstrating that CDK4 replaced the action of tumor promoters. These results suggest that expression of cyclin D1 upon ras activation synergizes with CDK4 overexpression. However, cyclin D1 transgenic mice and double transgenic mice for cyclin D1 and CDK4 did not show increased malignant progression in comparison to CDK4 transgenic mice. Biochemical analysis of tumors showed that CDK4 sequesters the CDK2 inhibitors p27Kip1 and p21Cip1, suggesting that indirect activation of CDK2 plays an important role in tumor development. These results indicate that, contrary to the general assumption, the catalytic subunit, CDK4, has higher oncogenic activity than cyclin D1, revealing a potential use of CDK4 as therapeutic target.}, number={10}, journal={ONCOGENE}, author={Marval, PLM and Macias, E and Conti, CJ and Rodriguez-Puebla, ML}, year={2004}, month={Mar}, pages={1863–1873} }