The ability to engage enterocyte apoptosis does not predict long-term crypt survival in p53 and Msh2 deficient mice

Sansom, Owen J.; Clarke, Alan R.

doi:10.1038/sj.onc.1205760

Cited by 15 publications

(13 citation statements)

References 32 publications

(37 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A total of 10 intact cross-sections were scored in each mouse for the number of 'live' crypts, defined as having at least six consecutive intact epithelial cells. On average, a cross-section of small intestine contains 125 crypts Brca2 deficiency in the murine small intestine T Hay et al or 15 Gy IR (P ¼ 0.04, n ¼ 3), suggesting that the ability to engage apoptosis does not precisely predict clonogenic survival in response to DNA damage, corroborating previous data for other gene dependancies (Sansom and Clarke, 2002). Despite the failure to precisely predict long-term survival from the apoptosis data, critically, Brca2-deficiency always reduced clonogenic survival following exposure to DNA damage.…”

supporting

confidence: 76%

Brca2 deficiency in the murine small intestine sensitizes to p53-dependent apoptosis and leads to the spontaneous deletion of stem cells

et al. 2005

Self Cite

View full text Add to dashboard Cite

The gene encoding the human BRCA2 tumour suppressor is mutated in a number of different tumour types, most notably inherited breast cancers. The primary role of BRCA2 is thought to lie in the maintenance of genomic stability via its role in the homologous recombination pathway. We generated mice in which Brca2 was deleted from virtually all cells within the adult small intestine, using a CYP1A1-driven Cre-Lox approach. We noted a significant p53-dependent increase in the levels of spontaneous apoptosis which persisted for several months after removal of the gene and ultimately we observed the spontaneous deletion of Brca2-deficient stem cells. Brca2 deficiency did not lead to gross changes in intestinal physiology but did enhance sensitivity to a variety of DNA crosslinking agents. Keywords: Brca2; p53; small intestine; apoptosis; DNA damageIn humans, inheritance of a single mutated copy of either of the tumour suppressor genes BRCA1 or BRCA2 predisposes to breast cancer, usually after loss of heterozygosity at the second allele (Scully, 2000). Rarely, inherited mutation of BRCA2 predisposes to cancer in other tissues, most commonly the ovary (The Breast Cancer Linkage Consortium, 1999). The products of the BRCA1 and BRCA2 genes are large, unrelated proteins, both believed to be independently involved in homologous recombination (HR), a process which allows for the error-free repair of DNA doublestrand breaks (DSBs) (Liu and West, 2002). BRCA2 is known to participate in this process through its direct interaction with RAD51, the mammalian equivalent of the bacterial RecA protein (Pellegrini et al., 2002). It is the breakdown in the HR pathway which is believed to be responsible for tumorigenesis in the absence of BRCA2, due to resulting genomic instability (Davies et al., 2001). Owing to embryonic lethality in mice homozygous for the Brca2-null allele (Ludwig et al. , 2004). Brca2 has also been deleted from cells of the developing thymus using an Lck-driven Cre-Lox system, resulting in a p53-dependent increase in the rate of spontaneous apoptosis in activated T cells (Cheung et al., 2002). These cells showed no significant difference in their apoptotic response to a variety of stimuli, including ionising radiation (IR) (Cheung et al., 2002). However, several studies have shown that cells lacking fully functional BRCA2, in both humans or mice, do exhibit increased sensitivity to DNA-damaging agents (Sharan et al., 1997;Abbott et al., 1998;Chen et al., 1998;Morimatsu et al., 1998;Patel et al., 1998;D'Andrea and Grompe, 2002;Kraakman-van der Zwet et al., 2002;Donoho et al., 2003).The purpose of our study was to analyse the effects of Brca2 deficiency in the murine adult small intestine, a tissue characterized by rapid cell turnover. We utilized a CYP1A1-specific inducible Cre-lox system to efficiently delete the Brca2 gene from crypt cells, including stem cells Sansom et al., 2004). Our results indicate that Brca2 plays an important role in the response to DNA damage in this tissue, that loss of Brca2 sensitizes c...

show abstract

supporting

confidence: 76%

Brca2 deficiency in the murine small intestine sensitizes to p53-dependent apoptosis and leads to the spontaneous deletion of stem cells

et al. 2005

Self Cite

View full text Add to dashboard Cite

show abstract

“…Similarly, colon tumor cell lines selected for cisplatin resistance did not present with defects in DNA MMR proteins (Sergent et al, 2002). Finally, in Msh2-deficient murine intestinal enterocytes, only a slightly reduced apoptotic response to cisplatin could be observed that did not influence the overall survival of crypt cells (Sansom and Clarke, 2002), and indications for the involvement of the p73 pathway were not found. We have previously generated an Msh2-deficient ES cell line (de Wind et al, 1995).…”

Section: Discussionmentioning

confidence: 87%

Msh2 deficiency does not contribute to cisplatin resistance in mouse embryonic stem cells

Claij

Riele

2004

Oncogene

View full text Add to dashboard Cite

Several reports have suggested that a defect in the DNA mismatch repair (MMR) system not only causes resistance to methylating agents but also confers low-level resistance to the chemotherapeutic drug cisplatin. Here we report that in a clonogenic assay, mouse embryonic stem (ES) cells deficient for the MMR protein MSH2 respond similarly as wild-type cells to cisplatin. Furthermore, restoring MSH2 expression in a cisplatin-resistant subclone selected from an Msh2 À/À cell population did not sensitize cells to cisplatin. To ascertain that our observations were not the result of a mutation in the Msh2 À/À cells that obscured the contribution of a defective MMR machinery to cisplatin resistance, we made use of the Cre-lox system to create a cell line in which the Msh2 gene can be conditionally inactivated. However, while de novo inactivation of Msh2 rendered cells tolerant to the methylating drug N-methyl-N 0 -nitro-N-nitrosoguanidine as expected, it did not alter the sensitivity to cisplatin. In addition, we were not able to derive cisplatin-resistant subclones from this freshly generated MMR-deficient cell line. Thus, in ES cells we did not find evidence for direct involvement of MMR deficiency in cisplatin resistance.

show abstract

“…For all these agents, we investigated the response 6 h following exposure, as this has previously been shown to report the maximal or near-maximal apoptotic response (e.g. Toft et al, 1999;Sansom and Clarke, 2002). In the case of ionizing radiation, gene deficiency has been linked with a delayed apoptotic response, for example, in the absence of p53 (Toft et al, 1999).…”

Section: Reduced Apoptosis In Mbd4-deficient Micementioning

confidence: 99%

“…We have previously shown that MMR-deficient mice have a compromised apoptotic response to a range of DNA-damaging agents in vivo including the alkylating agents temozolomide, NMNU and MNNG, cisplatin and nitrogen mustard (Toft et al, 1999;Sansom et al, 2001;Sansom and Clarke, 2002). Here we ask whether MBD4 mediates MMR-dependent apoptosis in the murine small intestine, and furthermore whether MBD4 is a general mediator of the apoptotic response.…”

Section: Introductionmentioning

confidence: 99%

MBD4 deficiency reduces the apoptotic response to DNA-damaging agents in the murine small intestine

et al. 2003

View full text Add to dashboard Cite

MBD4 was originally identified through its methyl binding domain, but has more recently been characterized as a thymine DNA glycosylase that interacts with the mismatch repair (MMR) protein MLH1. In vivo, MBD4 functions to reduce the mutability of methyl-CpG sites in the genome and mice deticient in MBD4 show increased intestinal tumorigenesis on an Apc Min/ þ background. As MLH1 and other MMR proteins have been functionally linked to apoptosis, we asked whether MBD4 also plays a role in mediating the apoptotic response within the murine small intestine. Mice deficient for MBD4 showed significantly reduced apoptotic responses 6 h following treatment with a range of cytotoxic agents including cirradiation, cisplatin, temozolomide and 5-fluorouracil (5-FU). This leads to increased clonogenic survival in vivo in Mbd4 À/À mice following exposure to either 5-FU or cisplatin. We next analysed the apoptotic response to 5-FU and temozolomide in doubly mutant Mbd4À/À mice but observed no additive decrease. The results imply that MBD4 and MLH1 lie in the same pathway and therefore that MMR-dependent apoptosis is mediated through MBD4. MBD4 deficiency also reduced the normal apoptotic response to c-irradiation, which we show is independent of Mlh1 status (at least in the murine small intestine), so suggesting that the reliance upon MBD4 may extend beyond MMR-mediated apoptosis. Our results establish a novel functional role for MBD4 in the cellular response to DNA damage and may have implications for its role in suppressing neoplasia.

show abstract

The ability to engage enterocyte apoptosis does not predict long-term crypt survival in p53 and Msh2 deficient mice

Cited by 15 publications

References 32 publications

Brca2 deficiency in the murine small intestine sensitizes to p53-dependent apoptosis and leads to the spontaneous deletion of stem cells

Brca2 deficiency in the murine small intestine sensitizes to p53-dependent apoptosis and leads to the spontaneous deletion of stem cells

Msh2 deficiency does not contribute to cisplatin resistance in mouse embryonic stem cells

MBD4 deficiency reduces the apoptotic response to DNA-damaging agents in the murine small intestine

Contact Info

Product

Resources

About