No abstract

Reliable approaches to identify stem cell mechanisms that mediate aggressive cancer could have great therapeutic value, based on the growing evidence of embryonic signatures in metastatic cancers. However, how to best identify and target stem-like mechanisms aberrantly acquired by cancer cells has been challenging. We harnessed the power of reprogramming to examine GRP78, a chaperone protein generally restricted to the endoplasmic reticulum in normal tissues, but which is expressed on the cell surface of human embryonic stem cells and many cancer types. We have discovered that (1) cell surface GRP78 (sGRP78) is expressed on iPSCs and is important in reprogramming, (2) sGRP78 promotes cellular functions in both pluripotent and breast cancer cells (3) overexpression of GRP78 in breast cancer cells leads to an induction of a CD24−/CD44+ tumor initiating cell (TIC) population (4) sGRP78+ breast cancer cells are enriched for stemness genes and appear to be a subset of TICs (5) sGRP78+ breast cancer cells show an enhanced ability to seed metastatic organ sites in vivo. These collective findings show that GRP78 has important functions in regulating both pluripotency and oncogenesis, and suggest that sGRP78 marks a stem-like population in breast cancer cells that has increased metastatic potential in vivo.

SUMMARY iPSCs show variable methylation patterns between lines, some of which reflect aberrant differences relative to ESCs. To examine whether this aberrant methylation results from genetic variation or non-genetic mechanisms, we generated human iPSCs from monozygotic twins to investigate how genetic background, clone, and passage number contribute. We found that aberrantly methylated CpGs are enriched in regulatory regions associated with MYC protein motifs and affect gene expression. We classified differentially methylated CpGs as being associated with genetic and/or non-genetic factors (clone, passage) and found that aberrant methylation preferentially occurs at CpGs associated with clone-specific effects. We further found that clone-specific effects play a strong role in recurrent aberrant methylation at specific CpG sites across different studies. Our results argue that a non-genetic biological mechanism underlies aberrant methylation in iPSCs, and that it is likely based on a probabilistic process involving MYC that takes place during or shortly after reprogramming.

Purpose: Testicular teratomas in adult patients are histologically diverse tumors that frequently coexist with other germ cell tumor (GCT) components. These mixed GCTs often metastasize to retroperitoneal lymph nodes where multiple GCT elements are frequently present in the same metastatic lesion. Neither the genetic relationships among the different components in metastatic lesions nor the relationships between primary and metastatic GCT components have been elucidated. Experimental Design: We examined metastases from 31 patients who underwent primary retroperitoneal lymph node dissection for metastatic testicular GCT. All patients had metastatic mature teratoma with one or more other GCTcomponents.This study included a total of 72 metastatic GCT components and 16 primary GCT components from 31 patients. Genomic DNA samples from each component were prepared from formalin-fixed, paraffin-embedded tissue sections using laser-assisted microdissection. Loss of heterozygosity (LOH) assays for seven microsatellite polymorphic markers on chromosomes 1p36 (D1S1646), 9p21 (D9S171and IFNA), 9q21 (D9S303), 13q22-q31 (D13S317), 18q22 (D18S543), and 18q21 (D18S60) were done to assess clonality. Results: Twenty-nine of 31 (94%) cases showed allelic loss in one or more components of the metastatic GCTs. Twenty-nine of 31mature teratomas showed allelic loss in at least one of seven microsatellite polymorphic markers analyzed. The frequency of allelic loss in informative cases of metastatic mature teratoma was 27% (8 of 30) with D1S1646, 34% (10 of 29) with D9S171, 37% (10 of 27) with IFNA, 27% (8 of 30) with D9S303, 46% (13 of 28) with D13S317, 26% (7 of 27) with D18S543, and 36% (10 of 28) with D18S60. Completely concordant allelic loss patterns between the mature teratoma and all of the other metastatic GCT components were seen in 26 of 29 cases in which the mature teratoma component showed LOH. Nearly identical allelic loss patterns were seen in the three remaining cases. In six cases analyzed, LOH patterns of each metastatic component were compared with each GCTcomponent of the primary testicular tumor. In all six cases, each primary and metastatic component showed an identical pattern of allelic loss. Conclusion: Our data support the common clonal origin of metastatic mature teratomas with other components of metastatic testicular GCTs and with each component of the primary tumor.Testicular germ cell tumors (GCT) are the most common solid malignancies in men between the ages of 20 and 45 years (1) and frequently metastasize to retroperitoneal lymph nodes. Teratomas show tremendous histologic diversity, containing a variety of tissue elements derived from all three embryonic germ cell layers. Mature teratomas are typically composed of differentiated tissues and may occur in the testes of both children and adults. However, the pathogenesis and behavior of these tumors are quite different in these two age groups with postpubertal patients having the potential for metastasis. Previous studies have shown that 22% to 4...

The heat shock protein GRP78 typically resides in the endoplasmic reticulum in normal tissues, but it has been shown to be expressed on the cell surface of several cancer cells, and some stem cells, where it can act as a signaling molecule by not-yet-fully defined mechanisms. Although cell surface GRP78 (sGRP78) has emerged as an attractive chemotherapeutic target, understanding how sGRP78 is functioning in cancer has been complicated by the fact that sGRP78 can function in a cell-context dependent manner, with a diverse array of reported binding partners, to regulate a variety of cellular responses. We had previously shown that sGRP78 was important in regulating pluripotent stem cell (PSC) functions, and hypothesized that embryonic-like mechanisms of GRP78 were critical to regulating aggressive breast cancer cell functions. Here, using proteomics we identify Dermcidin (DCD) as a novel sGRP78 binding partner common to both PSCs and breast cancer cells. We show that GRP78 and DCD cooperate to regulate stem cell and cancer cell migration that is dependent on the cell surface functions of these proteins. Finally, we identify Wnt/β-catenin signaling, a critical pathway in stem cell and cancer cell biology, as an important downstream intermediate in regulating this migration phenotype.