Biomedical subjects

Isidro Sánchez-García

Publications and source records attributed to Isidro Sánchez-García.

9 recordsLinked to original sources

PubMed2006

Killing time for cancer stem cells (CSC): discovery and development of selective CSC inhibitors.

Can cancer be cured or will it have to be controlled as a chronic disease? Despite a better understanding of the biology of tumour cells, the treatment of most cancers has not significantly changed for the past three decades. Are current cancer drugs targeted at the wrong kind of cells? Accumulating evidence has implicated that cancer is a disease of stem cells. In this context, a small fraction of cancer cells adopt the properties of stem cells. In some cases, the cancer stem cells (CSC) could be the close derivative of normal tissue stem cells. In either situation, the net result will be the same, in that CSC are the cells to be used as targets in the development of molecular and pharmaceutical therapies to treat and prevent human cancer. This could be a paradigm shift in the treatment of cancer, away from targeting the blast cells and towards the targeting of the CSC. A challenge to this approach will be to find a way to specifically target CSC without toxicity to normal cells. In this article, we propose how CSC can be used in therapy programs (target identification, drug discovery, etc.). Therefore, in the future, it might be possible to rid a patient of all his/her cancer cells, including the cancer stem cells.

Animals↗

PubMed2005

Mouse cDNA microarray analysis uncovers Slug targets in mouse embryonic fibroblasts.

There is a need to reveal mechanisms that account for maintenance of the mesenchymal phenotype in normal development and cancer. Slug (approved gene symbol Snai2), a member of the Snail gene family of zinc-finger transcription factors, is believed to function in the maintenance of the nonepithelial phenotype. This study identified candidate Slug target genes linked to Slug gene suppression in primary mouse embryonic fibroblasts. Expression analyses were performed with a mouse cDNA microarray (Mousechip-CNIO) containing 15,000 clones. A total of 15 novel Slug target species were validated by real-time PCR or Western analyses. These included self-renewal genes (Bmi1, Nanog, Gfi1), epithelial-mesenchymal genes (Tcfe2a, Ctnb1, Sin3a, Hdac1, Hdac2, Muc1, Cldn11), survival genes (Bcl2, Bbc3), and cell cycle/damage genes (Cdkn1a, Rbl1, Mdm2). Expression patterns were studied in wild-type MEFs and Slug-deficient MEFs. Slug-complementation studies recovered aberrant gene expression in cells lacking Slug, indicating that these genes were regulated directly by Slug. These results highlight their potential roles in mediating Slug function in mesenchymal cells and may help to identify novel therapeutic biomarkers in cancers linked to Slug.

Animals↗

PubMed2005

Cancer development induced by graded expression of Snail in mice.

The zinc-finger transcription factor Snail is believed to trigger epithelial-mesenchymal transitions (EMTs) during cancer progression. This idea is supported by analysis of Snail knockout mice, which uncovered crucial role of Snail in gastrulation, and of individuals with cancer, in whom Snail expression is frequently upregulated. However, these results have not shown a direct link between Snail and the pathogenesis of cancer. Here we show that mice carrying hypomorphic tetracycline-repressible Snail transgenes, that increase Snail expression to 20% above normal levels, exhibit no morphological alterations and develop both epithelial and mesenchymal tumours (leukaemias). Suppression of the Snail transgene did not rescue the malignant phenotype, indicating that alterations induced by Snail are irreversible. CombitTA-Snail murine embryonic fibroblasts show similar migratory ability to that of control mouse embryonic fibroblasts (MEFs). However, CombitTA-Snail-MEFs induce tumour formation in nude mice. CombitTA-Snail expression results in increased radioprotection in vivo, although it does not affect p53 regulation in response to DNA damage. In concert with these results, Snail expression is repressed following DNA damage. This regulation of Snail by DNA damage is p53-independent. Our results connect DNA damage with the requirement of a critical level of an EMT regulator and provide genetic evidence that Snail plays essential roles in cancer development in mammals and thereby influences cell fate in the genotoxic stress response.

Animals↗

PubMed2005

Immortalized mouse mammary fibroblasts lacking dioxin receptor have impaired tumorigenicity in a subcutaneous mouse xenograft model.

Although the dioxin receptor, the aryl hydrocarbon receptor (AhR), is considered a major regulator of xenobiotic-induced carcinogenesis, its role in tumor formation in the absence of xenobiotics is still largely unknown. Trying to address this question, we have produced immortalized cell lines from wild-type (T-FGM-AhR+/+) and mutant (T-FGM-AhR-/-) mouse mammary fibroblasts by stable co-transfection with the simian virus 40 (SV-40) large T antigen and proto-oncogenic c-H-Ras. Both cell lines had a myofibroblast phenotype and similar proliferation, doubling time, SV-40 and c-H-Ras expression and activity, and cell cycle distribution. AhR+/+ and AhR-/- cells were also equally able to support growth factor- and anchorage-independent proliferation. However, the ability of T-FGM-AhR-/- to induce subcutaneous tumors (leimyosarcomas) in NOD/SCID-immunodeficient mice was close to 4-fold lower than T-FGM-AhR+/+. In culture, T-FGM-AhR-/- had diminished migration in collagen-I and decreased lamellipodia formation. VEGFR-1/Flt-1, a VEGF receptor that regulates cell migration and blood vessel formation, was also down-regulated in AhR-/- cells. Signaling through the ERK-FAK-PKB/AKT-Rac-1 pathway, which contributes to cell motility and invasion, was also significantly inhibited in T-FGM-AhR-/-. Thus, the lower tumorigenic potential of T-FGM-AhR-/- could result from a compromised adaptability of these cells to the in vivo microenvironment, possibly because of an impaired ability to migrate and to respond to angiogenesis.

Animals↗

PubMed2005

SLUG in cancer development.

The SNAIL-related zinc-finger transcription factor, SLUG (SNAI2), is critical for the normal development of neural crest-derived cells and loss-of-function SLUG mutations have been proven to contribute to piebaldism and Waardenburg syndrome type 2 in a dose-dependent fashion. While aberrant induction of SLUG has been documented in cancer cells, relatively little is known about the consequences of SLUG overexpression in malignancy. To investigate the potential role of SLUG overexpression in development and in cancer, we generated mice carrying a tetracycline-repressible Slug transgene. These mice were morphologically normal at birth, and developed mesenchymal tumours (leukaemia and sarcomas) in almost all cases examined. Suppression of the Slug transgene did not rescue the malignant phenotype. Furthermore, the BCR-ABL oncogene, which induces Slug expression in leukaemic cells, did not induce leukaemia in Slug-deficient mice, implicating Slug in BCR-ABL leukaemogenesis in vivo. Overall, the findings indicate that while Slug overexpression is not sufficient to cause overt morphogenetic defects in mice, they demonstrate a specific and critical role for Slug in the pathogenesis of mesenchymal tumours.

Animals↗

PubMed2003

The radioresistance biological function of the SCF/kit signaling pathway is mediated by the zinc-finger transcription factor Slug.

Radiation-induced destruction of the hematopoietic system is the primary cause of death based on the findings that transfer of normal bone marrow cells prevents death from lethal irradiation. The stem cell factor-c-kit signaling pathway (SCF/c-kit) has been previously implicated in the hematopoietic recovery which prevents death from lethal irradiation, but the molecular mechanisms that mediate this biological effect are unknown. Since mutations on SCF, c-kit and Slug genes have a similar phenotype in mice, we examined if Slug could complement the radiosensitivity of kit-deficient mice. In this report, we show that Slug acts as a radioprotection agent as lack of Slug results in increased radiosensitivity. This effect cannot be recovered by activating SCF/c-kit in lethally irradiated Slug-deficient mice, as SCF-treated mice did not demonstrate stimulation of hematopoietic recovery leading to survival of the Slug-deficient mice. We found that we could complement the hematopoietic failure in lethally irradiated c-kit-deficient mice by transducing them with a TAT-Slug protein. We conclude that the zinc-finger transcription factor Slug is absolutely necessary for survival from lethal irradiation and identify Slug as the molecular target that mediates the radioprotection through SCF/c-kit. These results indicate that Slug may be a molecular component conferring radioresistance to cancer cells.

Animals↗

PubMed2002

SLUG (SNAI2) deletions in patients with Waardenburg disease.

Waardenburg syndrome (WS; deafness with pigmentary abnormalities) is a congenital disorder caused by defective function of the embryonic neural crest. Depending on additional symptoms, WS is classified into four types: WS1, WS2, WS3 and WS4. WS1 and WS3 are caused by mutations in PAX3, whereas WS2 is heterogenous, being caused by mutations in the microphthalmia (MITF) gene in some but not all affected families. The identification of Slugh, a zinc-finger transcription factor expressed in migratory neural crest cells, as the gene responsible for pigmentary disturbances in mice prompted us to analyse the role of its human homologue SLUG in neural crest defects. Here we show that two unrelated patients with WS2 have homozygous deletions in SLUG which result in absence of the SLUG product. We further show that Mitf is present in Slug-deficient cells and transactivates the SLUG promoter, and that Slugh and Kit genetically interact in vivo. Our findings further define the locus heterogeneity of WS2 and point to an essential role of SLUG in the development of neural crest-derived human cell lineages: its absence causes the auditory-pigmentary symptoms in at least some individuals with WS2.

Adolescent↗

PubMed2002

Zinc-finger transcription factor Slug contributes to the function of the stem cell factor c-kit signaling pathway.

The stem cell factor c-kit signaling pathway (SCF/c-kit) has been previously implicated in normal hematopoiesis, melanogenesis, and gametogenesis through the formation and migration of c-kit(+) cells. These biologic functions are also determinants in epithelial-mesenchymal transitions during embryonic development governed by the Snail family of transcription factors. Here we show that the activation of c-kit by SCF specifically induces the expression of Slug, a Snail family member. Slug mutant mice have a cell-intrinsic defect with pigment deficiency, gonadal defect, and impairment of hematopoiesis. Kit(+) cells derived from Slug mutant mice exhibit migratory defects similar to those of c-kit(+) cells derived from SCF and c-kit mutant mice. Endogenous Slug is expressed in migratory c-kit(+) cells purified from control mice but is not present in c-kit(+) cells derived from SCF mutant mice or in bone marrow cells from W/W(v) mice, though Slug is present in spleen c-kit(+) cells of W/W(v) (mutants expressing c-kit with reduced surface expression and activity). SCF-induced migration was affected in primary c-kit(+) cells purified from Slug-/- mice, providing evidence for a role of Slug in the acquisition of c-kit(+) cells with ability to migrate. Slug may thus be considered a molecular target that contributes to the biologic specificity to the SCF/c-kit signaling pathway, opening up new avenues for stem cell mobilization.

Anemia, Macrocytic↗

PubMed2002

Expression of the FUS domain restores liposarcoma development in CHOP transgenic mice.

Fusion proteins created by chromosomal abnormalities are key components of mesenchymal cancer development. The most common chromosomal translocation in liposarcomas, t(12;16)(q13;p11), creates the FUS-CHOP fusion gene. In the past, we generated FUS-CHOP and CHOP transgenic mice and have shown that while FUS-CHOP transgenic develop liposarcomas, mice expressing CHOP, which lacks the FUS domain, display essentially normal white adipose tissue (WAT) development, suggesting that the FUS domain of FUS-CHOP plays a specific and critical role in the pathogenesis of liposarcoma. To test the significance of FUS and CHOP domain interactions within a living mouse, we generated mice expressing the FUS domain and crossed them with CHOP-transgenic mice to generate double-transgenic FUSxCHOP animals. Here we report that expression of the FUS domain restores liposarcoma development in CHOP-transgenic mice. Our results provide genetic evidence that FUS and CHOP domains function in trans for the mutual restoration of liposarcoma. These results identify a new mechanism of tumor-associated fusion genes and might have impact beyond myxoid liposarcoma.

Adipocytes↗