The finite proliferative potential of normal human cells leads to replicative cellular senescence, which is a critical barrier to tumour progression in vivo1–3. We show that human p53 isoforms (Δ133p53 and p53β)4 constitute an endogenous regulatory mechanism for p53-mediated replicative senescence. Induced p53β and diminished Δ133p53 were associated with replicative senescence, but not oncogene-induced senescence, in normal human fibroblasts. The replicatively senescent fibroblasts also expressed increased levels of miR-34a, a p53-induced microRNA5–9, the antisense inhibition of which delayed the onset of replicative senescence. The siRNA-mediated knockdown of endogenous Δ133p53 induced cellular senescence, which was attributed to the regulation of p21WAF1 and other p53 transcriptional target genes. In overexpression experiments, while p53β cooperated with full-length p53 to accelerate cellular senescence, Δ133p53 repressed miR-34a expression and extended cellular replicative lifespan, providing a functional connection of this microRNA to the p53 isoform-mediated regulation of senescence. The senescence-associated signature of p53 isoform expression (i.e., elevated p53β and reduced Δ133p53) was observed in vivo in colon adenomas with senescent phenotypes10, 11. The increased Δ133p53 and decreased p53β isoform expression found in colon carcinoma may signal an escape from the senescence barrier during the progression from adenoma to carcinoma.

Although increased levels of both serum IL-6 and IL-8 are associated with lung cancer, only IL-8 levels are associated with lung cancer risk several years before diagnosis. Combination of IL-8 and CRP are more robust biomarkers than either marker alone in predicting subsequent lung cancer.

The bone marrow (BM) is a major organ of breast cancer (BC) dormancy and a common source of BC resurgence. Gap junctional intercellular communication (GJIC) between BC cells (BCCs) and BM stroma facilitates dormancy. This study reports on a hierarchy of BCCs with the most immature subset (Oct4hi/CD44hi/med/CD24−/+) demonstrating chemoresistance, dormancy, and stem cell properties: self-renewal, serial passaging ability, cycling quiescence, long doubling time, asymmetric division, high metastatic and invasive capability. In vitro and in vivo studies indicated that this subset was responsible for GJIC with BM stroma. Similar BCCs were detected in the blood of patients despite aggressive treatment and in a patient with a relatively large tumor but no lymph node involvement. In brief, these findings identified a novel BCC subset with stem cell properties, with preference for dormancy and in the circulation of patients. The findings establish a working cellular hierarchy of BCCs based on phenotype and functions.

The Notch signaling pathway is evolutionarily conserved and responsible for cell fate determination in the developing embryo and mature tissue. At the molecular level, ligand binding activates Notch signaling by liberating the Notch intracellular domain, which then translocates into the nucleus and activates gene transcription. Despite the elegant simplicity of this pathway, which lacks secondary messengers or a signaling cascade, Notch regulates gene expression in a highly context- and cell-type-dependent manner. Notch signaling is frequently dysregulated, most commonly by overactivation, across many cancers and confers a survival advantage on tumors, leading to poorer outcomes for patients. Recent studies demonstrate how Notch signaling increases tumor cell proliferation and provide evidence that active Notch signaling maintains the cancer stem-cell pool, induces epithelial-mesenchymal transition and promotes chemoresistance. These studies imply that pharmacological inhibition of Notch signaling may refine control of cancer therapy and improve patient survival. Gamma secretase inhibitors (GSIs) are drugs that inhibit Notch signaling and may be successful in controlling cancer cell growth in conjunction with standard chemotherapy, but substantial side effects have hampered their widespread use. Recent efforts have been aimed at the development of antibodies against specific Notch receptors and ligands with the hope of limiting side effects while providing the same therapeutic benefit as GSIs. Together, studies characterizing Notch signaling and modulation have offered hope that refined methods targeting Notch may become powerful tools in anticancer therapeutics.

A B S T R A C T PurposeChronic inflammation could play a role in lung carcinogenesis, underscoring the potential for lung cancer prevention and screening. We investigated the association of circulating high-sensitivity C-reactive protein (CRP, an inflammation biomarker) and CRP single nucleotide polymorphisms (SNPs) with prospective lung cancer risk. Patients and MethodsWe conducted a nested case-control study of 592 lung cancer patients and 670 controls with available prediagnostic serum and 378 patients and 447 controls with DNA within the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (N ϭ 77,464). Controls were matched to patients on age, sex, entry year, follow-up time, and smoking. We measured CRP levels in baseline serum samples and genotyped five common CRP SNPs. ResultsElevated CRP levels were associated with increased lung cancer risk (odds ratio [OR], 1.98; 95% CI, 1.35 to 2.89; P-trend Ͻ .001 for fourth quartile [Q4, Ն 5.6 mg/L] v Q1 [Ͻ 1.0 mg/L]). The CRP association did not differ significantly by histology, follow-up time, or smoking status, but was most apparent for squamous cell carcinomas (OR, 2.92; 95% CI, 1.30 to 6.54), 2 to 5 years before lung cancer diagnosis (OR, 2.33; 95% CI, 1.24 to 4.39), and among former smokers (OR, 2.48; 95% CI, 1.53 to 4.03) and current smokers (OR, 1.90; 95% CI, 1.06 to 3.41). Although CRP SNPs and haplotypes were associated with CRP levels, they were not associated with lung cancer risk. Ten-year standardized absolute risks of lung cancer were higher with elevated CRP levels among former smokers (Q4: 2.55%; 95% CI, 1.98% to 3.27% v Q1: 1.39%; 95% CI, 1.07% to 1.81%) and current smokers (Q4: 7.37%; 95% CI, 5.81% to 9.33% v Q1: 4.03%; 95% CI, 3.01% to 5.40%). ConclusionElevated CRP levels are associated with subsequently increased lung cancer risk, suggesting an etiologic role for chronic pulmonary inflammation in lung carcinogenesis.

Normal tissue homeostasis is maintained through asymmetric cell divisions that produce daughter cells with differing self-renewal and differentiation potentials. Certain tumor cell subfractions can self-renew and repopulate the heterogeneous tumor bulk, suggestive of asymmetric cell division, but an equally plausible explanation is that daughter cells of a symmetric division subsequently adopt differing cell fates. Cosegregation of template DNA during mitosis is one mechanism by which cellular components are segregated asymmetrically during cell division in fibroblast, muscle, mammary, intestinal, and neural cells. Asymmetric cell division of template DNA in tumor cells has remained elusive, however. Through pulsechase experiments with halogenated thymidine analogs, we determined that a small population of cells within human lung cancer cell lines and primary tumor cell cultures asymmetrically divided their template DNA, which could be visualized in single cells and in real time. Template DNA cosegregation was enhanced by cell-cell contact. Its frequency was density-dependent and modulated by environmental changes, including serum deprivation and hypoxia. In addition, we found that isolated CD133+ lung cancer cells were capable of tumor cell repopulation. Strikingly, during cell division, CD133 cosegregated with the template DNA, whereas the differentiation markers prosurfactant protein-C and pan-cytokeratins were passed to the opposing daughter cell, demonstrating that segregation of template DNA correlates with lung cancer cell fate. Our results demonstrate that human lung tumor cell fate decisions may be regulated during the cell division process. The characterization and modulation of asymmetric cell division in lung cancer can provide insight into tumor initiation, growth, and maintenance.cancer stem cell | CD133 | immortal DNA | template DNA

Cellular senescence contributes to aging and decline in tissue function. p53 isoform switching regulates replicative senescence in cultured fibroblasts and is associated with tumor progression. Here, we found that the endogenous p53 isoforms Δ133p53 and p53β are physiological regulators of proliferation and senescence in human T lymphocytes in vivo. Peripheral blood CD8 + T lymphocytes collected from healthy donors displayed an age-dependent accumulation of senescent cells (CD28 -CD57 + ) with decreased Δ133p53 and increased p53β expression. Human lung tumor-associated CD8 + T lymphocytes also harbored senescent cells. Cultured CD8 + blood T lymphocytes underwent replicative senescence that was associated with loss of CD28 and Δ133p53 protein. In poorly proliferative, Δ133p53-low CD8 + CD28 -cells, reconstituted expression of either Δ133p53 or CD28 upregulated endogenous expression of each other, which restored cell proliferation, extended replicative lifespan and rescued senescence phenotypes. Conversely, Δ133p53 knockdown or p53β overexpression in CD8 + CD28 + cells inhibited cell proliferation and induced senescence. This study establishes a role for Δ133p53 and p53β in regulation of cellular proliferation and senescence in vivo. Furthermore, Δ133p53-induced restoration of cellular replicative potential may lead to a new therapeutic paradigm for treating immunosenescence disorders, including those associated with aging, cancer, autoimmune diseases, and HIV infection.

The t(1;19) translocation yields a fusion between E2A and PBX1 genes and occurs in 5% of acute lymphoblastic leukemia in children and adults. We used chromosomal translocations and Ig heavy chain (IGH)͞T cell antigen receptor (TCR) rearrangements to develop an understanding of the etiology and natural history of this subtype of leukemia. We sequenced the genomic fusion between E2A and PBX1 in 22 preB acute lymphoblastic leukemias and two cell lines. The prenatal origin of the leukemia was assessed in 15 pediatric patients by screening for the clonotypic E2A-PBX1 translocation in neonatal blood spots, or Guthrie cards, obtained from the children at the time of birth. Two patients were determined to be weakly positive for the fusion at the time of birth, in contrast to previously studied childhood leukemia fusions, t(12;21), t(8;21), and t(4;11), which were predominantly prenatal. The presence of extensive N-nucleotides at the point of fusion in the E2A-PBX1 translocation as well as specific characteristics of the IGH͞TCR rearrangements provided additional evidence for a postnatal, preB cell origin. Intriguingly, 16 of 24 breakpoints on the 3.2-kb E2A intron 14 were located within 5 bp, providing evidence for a site-specific recombination mechanism. Breakpoints on the 232-kb PBX1 intron 1 were more dispersed but highly clustered proximal to exon 2. In sum, the translocation breakpoints displayed evidence of unique temporal, ontological, and mechanistic formation than the previously analyzed pediatric leukemia translocation breakpoints and emphasize the need to differentiate cytogenetic and molecular subgroups for studies of leukemia causality. P ediatric leukemias are a group of diverse diseases at the chromosome level, with various subtypes recognizable by recurrent translocations and aneuploidies. Although these genetic abnormalities help to categorize leukemias for treatment strategy and prognosis, they also may delineate specific causal pathways to malignancy. The consideration of individual molecular subtypes is providing clarity to epidemiological and biological studies. The best characterized example of this approach is the infant leukemias with MLL translocations (MLL ϩ ), for which epidemiologic associations and molecular analysis of breakpoints point to an in utero origin of the translocations, with reactive metabolites of genotoxic chemicals playing a potential key role (1-5). The MLL ϩ leukemias, along with the hyperdiploid subtype (leukemia clones with Ͼ50 chromosomes), also display significant associations with variants in genes encoding functional metabolic enzymes, thus implying a risk of leukemia imparted by the enzymes' substrates or products (6-8). Childhood leukemias with TEL-AML1 translocations, representing Ϸ25% of common acute lymphoblastic leukemia (cALL), share the in utero timing of translocation formation with MLL ϩ leukemias (9); however, there is currently no etiological mechanism for the formation of this translocation, apart from the nonhomologous end-joining processes that rejoin br...