Charles M. Perou

The Beige/Chediak-Higashi Syndrome Gene Encodes a Widely Expressed Cytosolic Protein

The human autosomal recessive disorder Chediak-Higashi syndrome and its murine homologue beigeare associated with the formation of giant lysosomes that cluster near the perinuclear region of cells. We prepared a polyclonal antiserum against a glutathione S-transferase-Beige fusion protein and demonstrated by Western analysis that the beige gene encodes a protein of 400 kDa that is expressed in cultured murine fibroblasts as well as most mouse tissues. The protein was not detected in either cultured fibroblasts or mouse tissues from two differentbeige mutants. Cultured fibroblasts transformed with multiple copies of yeast artificial chromosomes that contain the full-length beige gene showed much higher levels of Beige protein than either wild type fibroblasts or mouse tissues. Subcellular fractionation experiments demonstrated that the Beige protein was cytosolic and, under the conditions of isolation, had no measurable membrane association. Cultured mouse fibroblasts in which the Beige protein was overexpressed had smaller than normal lysosomes that were more peripherally distributed than in control cells. These findings, coupled with earlier published results, suggest that the Beige protein regulates lysosomal fission.

Complementation analysis of Chediak-Higashi Syndrome: The same gene may be responsible for the defect in all patients and species

Chediak-Higashi Syndrome is an autosomal recessive disorder, characterized by the presence of large intracellular granules, particularly lysosomes and melanosomes. While the Chediak-Higashi Syndrome is a rare disorder in humans, phenotypically similar syndromes are found in other species. Fusion of normal fibroblasts to Chediak fibroblasts complements the Chediak disorder, restoring normal lysosome size and distribution. Fusion of wild-type with Chediak fibroblasts from human, mouse, or mink demonstrates that wild-type fibroblasts can complement any of the Chediak fibroblasts. Complementation was not observed in interspecific hybrids between Chediak fibroblasts from these species, suggesting that the same gene product is defective in humans, mice, and mink.

PAM50 gene signatures and breast cancer prognosis with adjuvant anthracycline- and taxane-based chemotherapy: correlative analysis of C9741 (Alliance)

PAM50 intrinsic breast cancer subtypes are prognostic independent of standard clinicopathologic factors. CALGB 9741 demonstrated improved recurrence-free (RFS) and overall survival (OS) with 2-weekly dose-dense (DD) versus 3-weekly therapy. A significant interaction between intrinsic subtypes and DD-therapy benefit was hypothesized. Suitable tumor samples were available from 1,471 (73%) of 2,005 subjects. Multiplexed gene-expression profiling generated the PAM50 subtype call, proliferation score, and risk of recurrence score (ROR-PT) for the evaluable subset of 1,311 treated patients. The interaction between DD-therapy benefit and intrinsic subtype was tested in a Cox proportional hazards model using two-sided alpha=0.05. Additional multivariable Cox models evaluated the proliferation and ROR-PT scores as continuous measures with selected clinical covariates. Improved outcomes for DD therapy in the evaluable subset mirrored results from the complete data set (RFS; hazard ratio=1.20; 95% confidence interval=0.99–1.44) with 12.3-year median follow-up. Intrinsic subtypes were prognostic of RFS (P<0.0001) irrespective of treatment assignment. No subtype-specific treatment effect on RFS was identified (interaction P=0.44). Proliferation and ROR-PT scores were prognostic for RFS (both P<0.0001), but no association with treatment benefit was seen (P=0.14 and 0.59, respectively). Results were similar for OS. The prognostic value of PAM50 intrinsic subtype was greater than estrogen receptor/HER2 immunohistochemistry classification. PAM50 gene signatures were highly prognostic but did not predict for improved outcomes with DD anthracycline- and taxane-based therapy. Clinical validation studies will assess the ability of PAM50 and other gene signatures to stratify patients and individualize treatment based on expected risks of distant recurrence.

Patterns of cell cycle checkpoint deregulation associated with intrinsic molecular subtypes of human breast cancer cells

Genomic instability is a hallmark of breast cancer, contributes to tumor heterogeneity, and influences chemotherapy resistance. Although Gap 2 and mitotic checkpoints are thought to prevent genomic instability, the role of these checkpoints in breast cancer is poorly understood. Here, we assess the Gap 2 and mitotic checkpoint functions of 24 breast cancer and immortalized mammary epithelial cell lines representing four of the six intrinsic molecular subtypes of breast cancer. We found that patterns of cell cycle checkpoint deregulation were associated with the intrinsic molecular subtype of breast cancer cell lines. Specifically, the luminal B and basal-like cell lines harbored two molecularly distinct Gap 2/mitosis checkpoint defects (impairment of the decatenation Gap 2 checkpoint and the spindle assembly checkpoint, respectively). All subtypes of breast cancer cell lines examined displayed aberrant DNA synthesis/Gap 2/mitosis progression and the basal-like and claudin-low cell lines exhibited increased percentages of chromatid cohesion defects. Furthermore, a decatenation Gap 2 checkpoint gene expression signature identified in the cell line panel correlated with clinical outcomes in breast cancer patients, suggesting that breast tumors may also harbor defects in decatenation Gap 2 checkpoint function. Taken together, these data imply that pharmacological targeting of signaling pathways driving these phenotypes may lead to the development of novel personalized treatment strategies for the latter two subtypes which currently lack targeted therapeutic options because of their triple negative breast cancer status.Cell cycle: Breast cancer subtypes exhibit distinct checkpoint dysfunctionsUnique subtypes of breast cancer display distinctive patterns of genomic instability that affect cell division. Jacquelyn J. Bower and colleagues at the University of North Carolina at Chapel Hill, USA, assessed the molecular function of several G2-M cell cycle checkpoints—which ensure that cells don’t begin mitotic cell division until DNA replication is complete and they have had a chance to repair any damaged DNA—in 24 breast cancer and mammary epithelial cell lines that collectively represent four of the six intrinsic molecular subtypes of breast cancer. The distinct patterns of cell cycle checkpoint deregulation that the researchers found suggest that pharmacological targeting of the dysfunction in each type of breast cancer could lead to personalized treatment strategies. The findings also point to diagnostic biomarkers that could help predict patient responses to novel drugs or existing chemotherapies.

Additional file 1: Table S1. of Response and survival of breast cancer intrinsic subtypes following multi-agent neoadjuvant chemotherapy

Cox model DRFS analyses including intrinsic subtype in all patients from the MDACC-based cohort (GSE25066). Table S2. Cox model DRFS analyses including ROR-P in all patients from the MDACC-based cohort (GSE25066). Table S3. Cox model DRFS analyses including intrinsic subtype in patients that achieved a pCR from the MDACC-based cohort (GSE25066). Table S4. Cox model DRFS analyses including ROR-P in patients that achieved a pCR from the MDACC-based cohort (GSE25066). Table S5. Cox model DRFS analyses including ROR-P in patients with residual disease from the MDACC-based cohort (GSE25066). Table S6. Distribution of the PAM50 subtypes within the TNBCtype groups and vice versa. Table S7. Association of the TNBCtype subtypes with chemotherapy response in triple-negative breast cancer. Figure S1. CONSORT diagram of the various cohorts evaluated in this study. Figure S2. Kaplan-Meier distant relapse-free survival analysis in MDACC-based (GSE25066 [13]) dataset set. (A) Survival outcomes of the ROR-P groups in all patients. (B) Survival outcomes of the ROR-P groups in patients with clinically node-negative disease. Figure S3. Levels of ESR1 across TNBCtype ESR1-low group, TNBCtype ESR1-high group and ER+ group. Median expression of ESR1 in the PAM50 training dataset reported in Parker et al. [24] has been set to zero. Figure S4. Distribution of the TNBCtype subtypes and ESR1-high group within the PAM50 subtypes in TNBC. Figure S5. Distribution of the TNBCtype subtypes and ESR1-high group within the PAM50u2009+u2009Claudin-low subtypes in TNBC. Figure S6. Training and testing gene expression-based models predictive of pCR in all patients. Figure S7. Training and testing gene expression-based models predictive of pCR in patients with Basal-like disease. Figure S8. Training and testing gene expression-based models predictive of pCR in patients with luminal (A/B) disease. (DOCX 819 kb)

Chédiak–Higashi Syndrome

Current Opinion in Hematology 2008, 15:22–29 Purpose of review Chediak-Higashi syndrome, a rare autosomal recessive disorder, was described ove 50 years ago. Patients show hypopigmentation, recurrent infections, mild coagulation defects and varying neurologic problems. Treatment is bone marrow transplant, which is effective in treating the hematologic and immune defects, however the neurologic problems persist. The CHS1/LYST gene was identified over 10 years ago and homologous CHS1/LYST genes are present in all eukaryotes. This review will discuss the advances made in understanding the clinical aspects of the syndrome and the function of CHS1/LYST/Beige. Recent findings Clinical reports of Chediak-Higashi syndrome have identified mutations throughout the CHS1/LYST gene. The nature of the mutation can be a predictor of the severity of the disease. Over the past decade the CHS1/LYST family of proteins has been analyzed using model organisms, two-hybrid analysis, overexpression phenotypes and dominan negatives. These studies suggest that the CHS1/LYST protein is involved in either vesicle fusion or fission. Summary Although CHS is a rare disease, the Chediak-like family of proteins is providing insigh into the regulation of vesicle trafficking. Understanding the basic mechanisms that govern vesicle trafficking will provide essential information regarding how loss of CHS1/ LYST affects hematologic, immunologic and neurologic processes.