Our recent study showed critical roles of Dmp1 as a sensor of oncogenic Ras, HER2/neu signaling and activation of the Arf-p53 pathway. To elucidate the role of human DMP1 (hDMP1) in breast cancer, one hundred and ten pairs of human breast cancer specimen were studied for the alterations of the hDMP1-ARF-Hdm2-p53 pathway with follow up of clinical outcomes. Loss of heterozygosity (LOH) of the hDMP1 locus was found in 42% of human breast carcinomas, while that of INK4a/ARF and p53 were found in 20 and 34%, respectively. Hdm2 amplification was found in 13% of the same sample, which was found independently of LOH for hDMP1. Conversely, LOH for hDMP1 was found in mutually exclusive fashion with that of INK4a/ARF and p53, and was associated with low Ki67 index and diploid karyotype. Consistently, LOH for hDMP1 was associated with luminal A category and longer relapse-free survival, while that of p53 was associated with non-luminal A and shorter survival. Thus, loss of hDMP1 could define a new disease category associated with prognosis of breast cancer patients. Human breast epithelial cells/cancer cells with wild-type p53 were sensitive to growth inhibition by activated Dmp1:ER while those that delete p14ARF or p53, and/or Hdm2 amplification showed partial or nearly complete resistance, indicating that p53 is a critical target for hDMP1 to exhibit its biological activity.

Small cell lung cancer (SCLC) makes up almost 15% of all cases of lung cancer and occurs almost exclusively in individuals with a history of smoking (Blackhall & Faivre-Finn, 2011; Meyerson et al., 2004; Tamasi and Muller, 2011; Walenkamp et al., 2009). However, SCLCs differ significantly from NSCLCs in specific genetic alterations that occur. Moreover, smoking-damaged bronchial epithelia accompanying SCLCs appears to have undergone significantly more acquired genetic damage than is frequently found in NSCLCs. Two subtypes of SCLC exist: homogeneous small cell carcinoma and combined SCLC (mixture of any non-small cell type) (Meyerson et al., 2004; Tamasi and Muller, 2011). SCLC in its advanced stage has an aggressive clinical course and is commonly accompanied by paraneoplastic syndromes. Autocrine growth factors, such as neuroendocrine regulatory peptides (e.g. bombesin/gastrin-releasing peptide), are prominent in SCLC. SCLC is categorized as limited stage disease (LS) when confined to the ipsilateral hemithorax and within a single radiation port, while extensive stage disease (ES) includes metastatic disease outside the ipsilateral hemithorax (Blackhall & Faivre-Finn, 2011; Meyerson et al., 2004; Tamasi and Muller, 2011; Walenkamp et al., 2009). SCLC is sensitive to chemotherapy; response rates to front-line agents are often in the range of 60%, with approximately 10% of patients achieving a complete response, even in the setting of metastatic disease (Brambilla et al., 2009 Jemal et al., 2006). Despite this, the relapse rates are quite high and survival with currently available salvage therapy is quite modest. With current therapy, patients with LSSCLC have a median survival of 17 months and a 5-year overall survival rate of 12% , while patients with ES-SCLC have a median survival of 8.9 months, and a 5-year survival rate of approximately 2%. (Brambilla et al., 2009 Jemal et al., 2006; Tamasi and Muller, 2011). This article will review the molecular targeted agents, the genetic abnormalities, and therapeutic efficacy in SCLC.

Summary The transcription factor Dmp1 is a Ras/HER2-activated haplo-insufficient tumor suppressor that activates the Arf/p53 pathway of cell cycle arrest. Recent evidence suggests that Dmp1 may activate p53 independently of Arf in certain cell types. Here we report findings supporting this concept with the definition an Arf-independent function for Dmp1 in tumor suppression. We found that Dmp1 and p53 can interact directly in mammalian cells via the carboxyl-terminus of p53 and the DNA-binding domain of Dmp1. Expression of Dmp1 antagonized ubiquitination of p53 by Mdm2 and promoted nuclear localization of p53. Dmp1-p53 binding significantly increased the level of p53, independent of Dmp1’s DNA-binding activity. Mechanistically, p53 target genes were activated synergistically by co-expression of Dmp1 and p53 in p53−/−; Arf−/−cells and genotoxic responses of these genes were hampered more dramatically in Dmp1−/− and p53−/− cells than in Arf−/− cells. Together, our findings identify a robust new mechanism of p53 activation mediated through by direct physical interaction between Dmp1 and p53.

Cancer is caused by multiple genetic alterations leading to uncontrolled cell proliferation through multiple pathways. Malignant cells arise from a variety of genetic factors, such as mutations in tumor suppressor genes (TSGs) that are involved in regulating the cell cycle, apoptosis, or cell differentiation, or maintenance of genomic integrity. Tumor suppressor mouse models are the most frequently used animal models in cancer research. The anti-tumorigenic functions of TSGs, and their role in development and differentiation, and inhibition of oncogenes are discussed. In this review, we summarize some of the important transgenic and knockout mouse models for TSGs, including Rb, p53, Ink4a/Arf, Brca1/2, and their related genes.

Cancer is caused by multiple genetic alterations leading to uncontrolled cell proliferation through multiple pathways. Malignant cells arise from a variety of genetic factors, such as mutations in tumor suppressor genes (TSGs) that are involved in regulating the cell cycle, apoptosis, or cell differentiation, or maintenance of genomic integrity. Tumor suppressor mouse models are the most frequently used animal models in cancer research. The anti-tumorigenic functions of TSGs, and their role in development and differentiation, and inhibition of oncogenes are discussed. In this review, we summarize some of the important transgenic and knockout mouse models for TSGs, including Rb, p53, Ink4a/Arf, Brca1/2, and their related genes.

The use of biomarkers ensures breast cancer patients receive optimal treatment. Established biomarkers such as estrogen receptor (ER) and progesterone receptor (PR) have been playing significant roles in the selection and management of patients for endocrine therapy. HER2 is a strong predictor of response to trastuzumab. Recently, the roles of ER as a negative and HER2 as a positive indicator for chemotherapy have been established. Ki67 has traditionally been recognized as a poor prognostic factor, but recent studies suggest that measurement of Ki67-positive cells during treatment will more effectively predict treatment efficacy for both anti-hormonal and chemotherapy. p53 mutations are found in 20–35% of human breast cancers and are associated with aggressive disease with poor clinical outcome when the DNA-binding domain is mutated. The utility of cyclin D1 as a predictor of breast cancer prognosis is controversial, but cyclin D1b overexpression is associated with poor prognosis. Likewise, overexpression of the low molecular weight form of cyclin E1 protein predicts poor prognosis. Breast cancers from BRCA1/2 carriers often show high nuclear grades, negativity to ER/PR/HER2, and p53 mutations, and thus, are associated with poor prognosis. The prognostic values of other molecular markers, such as p14ARF, TBX2/3, VEGF in breast cancer are also discussed. Careful evaluation of these biomarkers with current treatment modality is required to determine whether their measurement or monitoring offer significant clinical benefits.