Bríd M. Ryan

Genetic variation in microRNA networks: the implications for cancer research.

Many studies have highlighted the role that microRNAs have in physiological processes and how their deregulation can lead to cancer. More recently, it has been proposed that the presence of single nucleotide polymorphisms in microRNA genes, their processing machinery and target binding sites affects cancer risk, treatment efficacy and patient prognosis. In reviewing this new field of cancer biology, we describe the methodological approaches of these studies and make recommendations for which strategies will be most informative in the future.

Survivin: A new target for anti-cancer therapy

Survivin is one of the most cancer-specific proteins identified to date, being upregulated in almost all human tumors. Biologically, survivin has been shown to inhibit apoptosis, enhance proliferation and promote angiogenesis. Because of its upregulation in malignancy and its key role in apoptosis, proliferation and angiogenesis, survivin is currently attracting considerable attention as a new target for anti-cancer therapies. In several animal model systems, downregulation of survivin or inactivation of its function has been shown to inhibit tumor growth. Strategies under investigation to target survivin include antisense oligonucleotides, siRNA, ribozymes, immunotherapy and small molecular weight molecules. The translation of these findings to the clinic is currently ongoing with a number of phase I/II clinical trials targeting survivin in progress. These include use of the antisense oligonucleotide LY2181308, the low molecular weight molecule inhibitor YM155 and survivin-directed autologous cytotoxic T lymphocytes. The optimum use of survivin antagonists in the treatment of cancer is likely to be in combination with conventional cancer therapies.

Microenvironmental modulation of asymmetric cell division in human lung cancer cells

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 pulse-chase 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.

ADAM-17 expression in breast cancer correlates with variables of tumor progression.

The ADAMs are a family of membrane proteins possessing a disintegrin and metalloprotease domain. One of their main functions is shedding of membrane proteins. The aim of this study was to test the hypothesis that ADAM-17 (also known as tumor necrosis factor-α converting enzyme) is involved in breast cancer progression. Overexpression of ADAM-17 in MCF-7 breast cancer cells increased in vitro invasion and proliferation, whereas down-regulation of ADAM-17 expression in MDA-MB-435 cells decreased invasion and proliferation. At both mRNA and protein levels, ADAM-17 expression was significantly up-regulated in breast cancer compared with normal breast tissue. Using Western blotting, ADAM-17 protein in breast cancer was shown to exist in two forms migrating with approximate molecular masses of 100 and 120 kDa. Based on their known molecular mass, these bands were taken to represent the active and precursor forms of ADAM-17, respectively. The proportion of active to total ADAM-17 increased progressively from normal breast tissue to primary breast cancer to lymph node metastases (P = 0.017, Kruskal-Wallis test). In primary cancers, the active form was expressed more frequently in node-positive compared with node-negative tumors (P = 0.034, χ2 test). Furthermore, in primary carcinomas, both forms of ADAM-17 correlated significantly (Spearman correlation analysis) with levels of urokinase plasminogen activator (precursor form: r = 0.246, P = 0.032, n = 83 and active form: r = 0.428, P = 0.0001, n = 83) and proliferating cell nuclear antigen (precursor form: r = 0.524, P < 0.0001, n = 73 and active form: r = 0.365, P = 0.002, n = 73). Our results support the hypothesis that ADAM-17 is involved in breast cancer progression.

ADAM-17 predicts adverse outcome in patients with breast cancer

ADAM-17 is a matrix metalloproteinase-like enzyme involved in the release of several ligands that have been shown to promote both cancer formation and progression. These ligands include transforming growth factor-alpha, amphiregulin, heparin-binding epidermal growth factor, epiregulin and tumor necrosis factor-alpha. In this investigation, we measured the expression of total ADAM-17 by enzyme-linked immunosorbent assay in 153 invasive breast cancers. We also measured the precursor and active forms by western blotting in 140 invasive breast cancers. Expression of ADAM-17 was significantly increased in high-grade compared with low-grade tumors and was independent of tumor size, lymph node metastasis and estrogen receptor status. Patients with high expression of ADAM-17 had a significantly shorter overall survival compared with those with low expression. Significantly, the prognostic impact of ADAM-17 was independent of conventional prognostic factors for breast cancer. Our results are further evidence that ADAM-17 is involved in breast cancer progression and thus provides further impetus for exploiting ADAM-17 as new target for cancer treatment.

rs4919510 in hsa-mir-608 Is Associated with Outcome but Not Risk of Colorectal Cancer

Background Colorectal cancer is the third most incident cancer and cause of cancer-related death in the United States. MicroRNAs, a class of small non-coding RNAs, have been implicated in the pathogenesis and prognosis of colorectal cancer, although few studies have examined the relationship between germline mutation in the microRNAs with risk and prognosis. We therefore investigated the association between a SNP in hsa-mir-608, which lies within the 10q24 locus, and colorectal cancer. Methods and Results A cohort consisting of 245 cases and 446 controls was genotyped for rs4919510. The frequency of the GG genotype was significantly higher in African Americans (15%) compared to Caucasians (3%) controls. There was no significant association between rs4919510 and colorectal cancer risk (African American: ORGG vs. CC 0.89 [95% CI, 0.41–1.80]) (Caucasian: ORGG vs. CC 1.76, ([95% CI, 0.48–6.39]). However, we did observe an association with survival. The GG genotype was associated with an increased risk of death in Caucasians (HRGG vs. CC 3.54 ([95% CI, 1.38–9.12]) and with a reduced risk of death in African Americans (HRGG vs. CC 0.36 ([95% CI 0.12–1.07). Conclusions These results suggest that rs4910510 may be associated with colorectal cancer survival in a manner that is dependent on race.

A Combined Prognostic Serum Interleukin-8 and Interleukin-6 Classifier for Stage 1 Lung Cancer in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial

Background: The advent of low-dose helical computed tomography for lung cancer screening will likely lead to an increase in the detection of stage I lung cancer. Presently, these patients are primarily treated with surgery alone and approximately 30% will develop recurrence and die. Biomarkers that can identify patients for whom adjuvant chemotherapy would be a benefit could significantly reduce both patient morbidity and mortality. Herein, we sought to build a prognostic inflammatory–based classifier for stage I lung cancer. Methods: We performed a retrospective analysis of 548 European American lung cancer cases prospectively enrolled in the Prostate, Lung, Colorectal and Ovarian study. C-reactive protein, interleukin (IL)-6, IL-8, tumor necrosis factor-&agr;, and IL-1&bgr; were measured using an ultrasensitive electrochemiluminescence immunoassay in serum samples collected at the time of study entry. Results: IL-6 and IL-8 were each associated with significantly shorter survival (hazard ratio [HR], 1.33; 95% confidence interval [CI], 1.08–1.64; p = 0.007; and HR, 1.3; 95% CI, 1.09–1.67; p = 0.005, respectively). Moreover, a combined classifier of IL-6 and IL-8 were significantly associated with poor outcome in stage I lung cancer patients (HR, 3.39; 95% CI, 1.54–7.48, p = 0.002) and in stage 1 patients with more than or equal to 30 pack-years of smoking (HR, 3.15; 95% CI, 1.54–6.46, p = 0.002). Conclusions: These results further support the association between inflammatory markers and lung cancer outcome and suggest that a combined serum IL-6/IL-8 classifier could be a useful tool for guiding therapeutic decisions in patients with stage I lung cancer.

KRAS-LCS6 Genotype as a Prognostic Marker in Early-Stage CRC–Letter

In their recently published study (1), Smits and colleagues reported an association between rs61764370 and colorectal cancer (CRC) survival of early-stage tumors. Similarly, in our study of 678 (441 controls and 237 cases; [Table 1][1]), we found that rs61764370 was also associated with a reduced

MDM2 SNP285 does not antagonize the effect of SNP309 in lung cancer

Conflicting reports exist regarding the contribution of SNP309 in MDM2 to cancer risk. Recently, SNP285 was shown to act as an antagonist to SNP309 by overriding the effect of SNP309 on SP1‐mediated transcription. Moreover, SNP285 modified the relationship between SNP309 and risk of breast, ovarian and endometrial cancer. We assessed whether SNP285 confounded the effect of SNP309 in lung cancer in a cohort of 720 controls and 556 cases. Our cohort included both Caucasians and African Americans. Neither SNP309 nor SNP285 was associated with lung cancer risk or survival. In addition, removal of individuals who carried the variant C allele of SNP285 did not modify the association between SNP309 with either lung cancer risk or survival. Although an effect of SNP285 has been demonstrated in breast, ovarian and endometrial cancer, our findings do not support a role for this SNP in lung cancer and raise the possibility that the effect of SNP285 is restricted to cancers in women.

Mammaglobin a in breast cancer: Existence of multiple molecular forms

Existing serum‐based markers for breast cancer all lack organ specificity. Mammaglobin A (MGA) is a 93 amino acid protein expressed almost exclusively in breast tissue. The aim of our study was to investigate the different forms of MGA protein in fibroadenomas and breast carcinomas. MGA protein was measured by Western blotting in 132 breast cancers, 29 fibroadenomas and 14 nonbreast tissues. MGA protein in breast tissue was found to exist in 2 main forms. These forms migrated with approximate molecular masses of 18 and 25 kDa. Both forms of MGA were detected more frequently in breast carcinomas compared to fibroadenomas. The high molecular weight form of MGA but not the low molecular weight form was found more frequently in hormone receptor‐positive than in receptor‐negative cancers. Furthermore, an inverse relationship was found between the high molecular weight form of MGA and both tumour grade and proliferation index. No significant correlation was found between the MGA proteins and either tumor size or nodal status. Our results show that MGA protein exists in 2 main forms in breast tissue. As the high molecular weight form correlated positively with hormone receptors and negatively with tumor grade and proliferation rate, its presence is likely to be associated with a favourable prognosis for breast cancer. As expression of MGA is almost breast specific, it is a promising marker for breast cancer. Its most immediate use is likely to be in detecting micrometastases from breast cancer.