Nicola Barnard

High expression of lymphocyte-associated genes in node-negative HER2+ breast cancers correlates with lower recurrence rates.

Gene expression analysis has identified biologically relevant subclasses of breast cancer. However, most classification schemes do not robustly cluster all HER2+ breast cancers, in part due to limitations and bias of clustering techniques used. In this article, we propose an alternative approach that first separates the HER2+ tumors using a gene amplification signal for Her2/neu amplicon genes and then applies consensus ensemble clustering separately to the HER2+ and HER2- clusters to look for further substructure. We applied this procedure to a microarray data set of 286 early-stage breast cancers treated only with surgery and radiation and identified two basal and four luminal subtypes in the HER2- tumors, as well as two novel and robust HER2+ subtypes. HER2+ subtypes had median distant metastasis-free survival of 99 months [95% confidence interval (95% CI), 83-118 months] and 33 months (95% CI, 11-54 months), respectively, and recurrence rates of 11% and 58%, respectively. The low recurrence subtype had a strong relative overexpression of lymphocyte-associated genes and was also associated with a prominent lymphocytic infiltration on histologic analysis. These data suggest that early-stage HER2+ cancers associated with lymphocytic infiltration are a biologically distinct subtype with an improved natural history.

Autophagy Opposes p53-Mediated Tumor Barrier to Facilitate Tumorigenesis in a Model of PALB2-Associated Hereditary Breast Cancer

Hereditary breast cancers stem from germline mutations in susceptibility genes such as BRCA1, BRCA2, and PALB2, whose products function in the DNA damage response and redox regulation. Autophagy is an intracellular waste disposal and stress mitigation mechanism important for alleviating oxidative stress and DNA damage response activation; it can either suppress or promote cancer, but its role in breast cancer is unknown. Here, we show that similar to Brca1 and Brca2, ablation of Palb2 in the mouse mammary gland resulted in tumor development with long latency, and the tumors harbored mutations in Trp53. Interestingly, impaired autophagy, due to monoallelic loss of the essential autophagy gene Becn1, reduced Palb2-associated mammary tumorigenesis in a Trp53-wild-type but not conditionally null background. These results indicate that, in the face of DNA damage and oxidative stress elicited by PALB2 loss, p53 is a barrier to cancer development, whereas autophagy facilitates cell survival and tumorigenesis.

Loss of types XV and XIX collagen precedes basement membrane invasion in ductal carcinoma of the female breast

Ductal and lobular carcinomas comprise most malignancies of the female breast and the morbidity and mortality associated with breast cancer. During the progression from in situ to invasive stages, tumour cells penetrate the epithelial and vascular basement membranes (BM) to realize full metastatic potential. While the definition of these structures has primarily resulted from analysis of laminin and type IV collagen, characterization of newly discovered BM/BM zone (BMZ) proteins will further elucidate the interactions between tumour cells and the host stroma. We have studied the expression of two non‐fibrillar BMZ collagens, the type XV proteoglycan and collagen XIX, in breast cancer where a linear, well‐formed BM becomes fragmented and even lost in the progression of epithelial malignancy. In the normal breast, types XV and XIX were found in all BMZ: epithelial, muscle, neural, endothelial, and fat. In in situ lesions, these two collagens, and particularly type XV, were often absent from the BM/BMZ displaying a continuous or just focally disrupted type IV/laminin staining pattern. In contrast, infiltrating ductal carcinomas showed only rare traces of laminin and collagen IV reactivity adjacent to the glands and tumour nests, and similarly there was little if any evidence of types XV and XIX collagen. All four molecules were, however, detected in the interstitium associated with some of the invasive carcinomas. The data suggest that types XV and XIX collagen are lost early in the development of invasive tumours, prior to penetration and eventual dissolution of the epithelial BM. Disappearance of these proteins from the BM/BMZ may signal remodelling of the extracellular matrix to promote tumour cell infiltration. Copyright

The Inverse Relationship Between Microvessel Counts and Tumor Volume in Breast Cancer

Abstract: Angiogenesis has emerged as an indicator of metastatic potential in invasive breast cancer. Exponential tumor growth and the appearance of metastasis are observed as new microvessels form. We postulated that the relevance of angiogenesis would be enhanced if analyzed as a function of tumor volume rather than greatest diameter alone and that microvessel counts would proportionately increase as does volume. Since tumors are three‐dimensional solids, volume was calculated using the formula for an ellipsoid, V = π/6 (a×b×c). Sixty‐four tumors 2.5 cm were studied and analyzed in 5 mm incremental ranges. Mean microvessel counts did not vary significantly among these tumor size groups. However, analysis of microvessel counts as a function of tumor volume decreased from 947.1/cm3 (0–0.5 cm) to 18.1/cm3 (2.1–2.5 cm), a greater than 50‐fold difference. High microvessel density in small cancers supports the notion of metastasis as an early event, making these small tumors perhaps ideal targets for antiangiogenic agents.

Autophagy Regulates Keratin 8 Homeostasis in Mammary Epithelial Cells and in Breast Tumors

Autophagy is activated in response to cellular stressors and mediates lysosomal degradation and recycling of cytoplasmic material and organelles as a temporary cell survival mechanism. Defective autophagy is implicated in human pathology, as disruption of protein and organelle homeostasis enables disease-promoting mechanisms such as toxic protein aggregation, oxidative stress, genomic damage, and inflammation. We previously showed that autophagy-defective immortalized mouse mammary epithelial cells are susceptible to metabolic stress, DNA damage, and genomic instability. We now report that autophagy deficiency is associated with endoplasmic reticulum (ER) and oxidative stress, and with deregulation of p62-mediated keratin homeostasis in mammary cells, allograft tumors, and mammary tissues from genetically engineered mice. In human breast tumors, high phospho(Ser73)-K8 levels are inversely correlated with Beclin 1 expression. Thus, autophagy preserves cellular fitness by limiting ER and oxidative stress, a function potentially important in autophagy-mediated suppression of mammary tumorigenesis. Furthermore, autophagy regulates keratin homeostasis in the mammary gland via a p62-dependent mechanism. High phospho(Ser73)-K8 expression may be a marker of autophagy functional status in breast tumors and, as such, could have therapeutic implications for breast cancer patients. Mol Cancer Res; 8(6); 873–84. ©2010 AACR.

A 2D Mechanistic Model of Breast Ductal Carcinoma in Situ (DCIS) Morphology and Progression

Ductal carcinoma in situ (DCIS) of the breast is a non-invasive tumor in which cells proliferate abnormally, but remain confined within a duct. Although four distinguishable DCIS morphologies are recognized, the mechanisms that generate these different morphological classes remain unclear, and consequently the prognostic strength of DCIS classification is not strong. To improve the understanding of the relation between morphology and time course, we have developed a 2D in silico particle model of the growth of DCIS within a single breast duct. This model considers mechanical effects such as cellular adhesion and intra-ductal pressure, and biological features including proliferation, apoptosis, necrosis, and cell polarity. Using this model, we find that different regions of parameter space generate distinct morphological subtypes of DCIS, so elucidating the relation between morphology and time course. Furthermore, we find that tumors with similar architectures may in fact be produced through different mechanisms, and we propose future work to further disentangle the mechanisms involved in DCIS progression.

TESTICULAR GERM CELL TUMORS : MOLECULAR UNDERSTANDING AND CLINICAL IMPLICATIONS

It was recognized in the 1960s that testicular germ cell tumors were curable with chemotherapeutic drugs. Since that time, newer drugs including cisplatin have increased the cure rate of these tumors to over 80%, even in patients with metastatic disease. Germ cell tumors also exhibit a unique biology and genetics that distinguish them from other solid tumors and might contribute to their routine curability.

A genetic variant in a PP2A regulatory subunit encoded by the PPP2R2B gene associates with altered breast cancer risk and recurrence

A recent candidate gene association study identified a single nucleotide polymorphism (SNP) in the PPP2R2B gene (rs319217, A/G) that manifests allelic differences in the cellular responses to treatment with chemotherapeutic agents (Vazquez et al., Nat Rev Drug Discov 2008;7:979‐87). This gene encodes a regulatory subunit of protein phosphatase 2A (PP2A), one of the major Ser/Thr phosphatases implicated in the negative control of cell growth and division. Given the tumor suppressor activities of PP2A, here we evaluate whether this genetic variant associates with the age of diagnosis and recurrence of breast cancer in women. To investigate the linkage disequilibrium in the vicinity of this SNP, PPP2R2B haplotypes were analyzed using HapMap data for 90 Caucasians. It is found that the A variant of rs319217 tags a haplotype that appears to be under positive selection in the Caucasian population, implying that this SNP is functional. Subsequently, associations with cellular responses were investigated using data reported by the NCI anticancer drug screen and associations with breast cancer clinical variables were analyzed in a cohort of 819 Caucasian women. The A allele associates with a better response of tumor derived cell lines, lower risk of breast cancer recurrence, later time to recurrence, and later age of diagnosis of breast cancer in Caucasian women. Taken together these results indicate that the A variant of the rs319217 SNP is a marker of better prognosis in breast cancer.

Metabotropic glutamate receptor-1 contributes to progression in triple negative breast cancer.

TNBC is an aggressive breast cancer subtype that does not express hormone receptors (estrogen and progesterone receptors, ER and PR) or amplified human epidermal growth factor receptor type 2 (HER2), and there currently exist no targeted therapies effective against it. Consequently, finding new molecular targets in triple negative breast cancer (TNBC) is critical to improving patient outcomes. Previously, we have detected the expression of metabotropic glutamate receptor-1 (gene: GRM1; protein: mGluR1) in TNBC and observed that targeting glutamatergic signaling inhibits TNBC growth both in vitro and in vivo. In this study, we explored how mGluR1 contributes to TNBC progression, using the isogenic MCF10 progression series, which models breast carcinogenesis from nontransformed epithelium to malignant basal-like breast cancer. We observed that mGluR1 is expressed in human breast cancer and that in MCF10A cells, which model nontransformed mammary epithelium, but not in MCF10AT1 cells, which model atypical ductal hyperplasia, mGluR1 overexpression results in increased proliferation, anchorage-independent growth, and invasiveness. In contrast, mGluR1 knockdown results in a decrease in these activities in malignant MCF10CA1d cells. Similarly, pharmacologic inhibition of glutamatergic signaling in MCF10CA1d cells results in a decrease in proliferation and anchorage-independent growth. Finally, transduction of MCF10AT1 cells, which express c-Ha-ras, using a lentiviral construct expressing GRM1 results in transformation to carcinoma in 90% of resultant xenografts. We conclude that mGluR1 cooperates with other factors in hyperplastic mammary epithelium to contribute to TNBC progression and therefore propose that glutamatergic signaling represents a promising new molecular target for TNBC therapy.

Calcitonin-Negative Neuroendocrine Tumor of the Thyroid: A Distinct Clinical Entity

BACKGROUND Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor (NET) that arises from the parafollicular cells (C-cells) of the thyroid gland which produces calcitonin (CT) and is, therefore, a serum and immunohistochemical biomarker of MTC. Here, we describe a patient with another form of NET arising with the thyroid gland. PATIENT FINDINGS This is a forty-year-old woman who underwent total thyroidectomy for a thyroid nodule that had features of an NET on fine needle aspiration. Her serum CT and carcinoembryonic antigen were normal. Surgical pathology showed a well-differentiated NET with immunohistochemical stains positive for markers of follicular cells (thyroglobulin and synaptophysin), positive for neuroendocrine markers (neuron specific enolase and chromogranin A), but negative for CT, the defining marker of MTC. CONCLUSIONS We describe a rare case of a nonmedullary NET of the thyroid gland arising from thyroid follicular cells, not parafollicular cells. We suggest that calcitonin-negative neuroendocrine tumor of the thyroid gland (CNNETT) may be an entity that has not been recognized in the literature. This distinction between MTC and CNNETT may be important, as the treatment and prognosis may differ.