A change in chromosome number, known as aneuploidy, is a common characteristic of cancer. Aneuploidy disrupts gene expression in human cancer cells and immortalized human epithelial cells, but not in normal human cells. However, the relationship between aneuploidy and cancer remains unclear. To study the effects of aneuploidy in normal human cells, we generated artificial cells of human primary fibroblast having three chromosome 8 (trisomy 8 cells) by using microcell-mediated chromosome transfer technique. In addition to decreased proliferation, the trisomy 8 cells lost contact inhibition and reproliferated after exhibiting senescence-like characteristics that are typical of transformed cells. Furthermore, the trisomy 8 cells exhibited chromosome instability, and the overall gene expression profile based on microarray analyses was significantly different from that of diploid human primary fibroblasts. Our data suggest that aneuploidy, even a single chromosome gain, can be introduced into normal human cells and causes, in some cases, a partial cancer phenotype due to a disruption in overall gene expression.

Ionizing radiation is one of a few well-characterized etiologic factors of human breast cancer. Laboratory rodents serve as useful experimental models for investigating dose responses and mechanisms of cancer development. Using these models, a lot of information has been accumulated about mammary gland cancer, which can be induced by both chemical carcinogens and radiation. In this review, we first list some experimental rodent models of breast cancer induction. We then focus on several topics that are important in understanding the mechanisms and risk modification of breast cancer development, and compare radiation and chemical carcinogenesis models. We will focus on the pathology and natural history of cancer development in these models, genetic changes observed in induced cancers, indirect effects of carcinogens, and finally risk modification by reproductive factors and age at exposure to the carcinogens. In addition, we summarize the knowledge available on mammary stem/progenitor cells as a potential target of carcinogens. Comparison of chemical and radiation carcinogenesis models on these topics indicates certain similarities, but it also indicates clear differences in several important aspects, such as genetic alterations of induced cancers and modification of susceptibility by age and reproductive factors. Identification of the target cell type and relevant translational research for human risk management may be among the important issues that are addressed by radiation carcinogenesis models.JRRS Incentive Award in 2009.

To better understand the molecular basis of radiation-induced osteosarcoma (OS), we performed global gene expression profiling of rat OS tumors induced by the bone-seeking alpha emitter 238 Pu, and the expression profiles were compared with those of normal osteoblasts (OB). The expressions of 72 genes were significantly differentially expressed in the tumors related to OB. These included genes involved in the cell adhesion (e.g., Podxl, Col18a1, Cd93, Emcn and Vcl), differentiation, developmental processes (e.g., Hhex, Gata2, P2ry6, P2rx5, Cited2, Osmr and Igsf10), tumorsuppressor function (e.g., Nme3, Blcap and Rrm1), Src tyrosine kinase signaling (e.g., Hck, Shf, Arhgap29, Cttn and Akap12), and Wnt/b-catenin signaling (e.g., Fzd6, Lzic, Dkk3 and Ctnna1) pathways. Expression changes of several genes were validated by quantitative real-time RT-PCR analysis. Notably, all of the identified genes involved in the Wnt/b-catenin signaling pathway were known or proposed to be negative regulators of this pathway and were downregulated in the tumors, suggesting the activation of bcatenin in radiation-induced OS. By using immunohistochemical and immunoblot analyses, constitutive activation of the Wnt/b-catenin signaling pathway in the tumors was confirmed by observing nuclear and/or cytoplasmic localization of b-catenin and a decrease in its inactive (phosphorylated) form. Furthermore, we found a significant reduction in the levels of glycogen synthase kinase 3b (GSK-3b) protein in the tumors relative to OB. Taken together, these findings provide new insights into the molecular basis of radiation-induced OS. ' UICCKey words: osteosarcoma; osteoblast; ionizing radiation; carcinogenesis; transcriptome Osteosarcoma (OS) is the most common primary tumor of bone in children and adolescents. The peak incidence of OS occurs in the second decade of life, with an additional smaller peak in the elderly population. This tumor is highly aggressive and is thought to arise primarily from osteoblasts (OB), boneforming cells. An increased risk for developing OS is known to be associated with some genetic disorders, such as hereditary retinoblastoma and Li-Fraumeni syndrome with germline mutations in the retinoblastoma (RB1) and TP53 genes, respectively. 1,2 In agreement with this, abnormalities of genes involved in the RB1 and TP53 tumor-suppressor pathways are often found in OS. 3,4 On the other hand, the association between ionizing radiation and the subsequent development of OS has been well documented in prior studies. For example, OS is known as one of the most frequent secondary malignant neoplasms occurring within the radiation field in patients, especially with retinoblastoma, treated with radiation therapy. 1,5 The risk of OS has been reported to be increased following the internal exposure to bone-seeking radioisotopes from occupational or medicinal use. 6-8 Interestingly, some studies have revealed the genetic and cytogenetic changes in radiation-induced OS and suggested the presence of additional tumor-associated genes. ...

(111)In-labeled trastuzumab modified with nuclear localizing signal (NLS) peptides ((111)In-trastuzumab-NLS) efficiently delivers an Auger electron (AE) emitter (111)In into the cell nucleus and is thus a promising radiopharmaceutical in AE radioimmunotherapy (AE-RIT) for targeted killing of HER2-positive cancer. However, further improvement of its therapeutic efficacy is required. In this study, the authors show a transcriptomic approach to identify potential targets for enhancing the cytotoxic effects of (111)In-trastuzumab-NLS. They generated two types of (111)In-trastuzumab-NLS harboring different numbers of NLS peptides, (111)In-trastuzumab-NLS-S and -L. These radioimmunoconjugates (230 and 460 kBq) showed a significant higher cytotoxicity to SKBR3 human breast cancer cells overexpressing HER2 compared to (111)In-trastuzumab. Microarray analysis revealed that NF-kB-related genes (38 genes) were significantly changed in transcription by (111)In trastuzumab-NLS-L (230 kBq) treatment. Quantitative reverse transcription polymerase chain reaction confirmed the microarray data by showing transcriptional alternation of selected NF-κB target genes in cells treated with (111)In-trastuzumab-NLS-L. Interestingly, bortezomib, a drug known as a NF-κB modulator, significantly enhanced the cytotoxicity of (111)In-trastuzumab-NLS-L in SKBR3 cells. Taken together, the transcriptome data suggest the possibility that the modulation of NF-kB signaling activity is a molecular signature of (111)In-trastuzumab-NLS and coadministration of bortezomib may be efficacious in enhancement of AE-RIT with (111)In-trastuzumab-NLS.

Previous studies have shown that induction of some genes by low-dose radiation has a different dependence on the time after irradiation than induction by high doses. To examine the mechanisms underlying this phenomenon, we investigated the changes in the time course of the rates of transcription of genes in cells of the human myeloblastic leukemia cell line ML-1 by a nuclear run-on assay. It is possible that the more rapid induction of the mRNA of the CDKN1A and GADD45 genes after exposure to 50 cGy of X rays than after 20 Gy is due to a lower level of stabilization of the mRNA of these genes after 50 cGy. In addition, our results show that 50 cGy of X rays increases the transcription rates of the CDKN1A and GADD45 genes, with a maximum induction at 0.5 to 1 h after irradiation, much earlier than the maximum accumulation of stabilized TP53 protein. We suggest the involvement of BRCA1 protein in the early induction of transcription of these two genes.