Showing papers by "Johan Vallon-Christersson published in 2012"

Molecular Profiling Reveals Low- and High-Grade Forms of Primary Melanoma

Abstract: Purpose: For primary melanomas, tumor thickness, mitotic rate, and ulceration are well-laid cornerstones of prognostication. However, a molecular exposition of melanoma aggressiveness is critically missing. We recently uncovered a four-class structure in metastatic melanoma, which predicts outcome and informs biology. This raises the possibility that a molecular structure exists even in the early stages of melanoma and that molecular determinants could underlie histophenotype and eventual patient outcome. Experimental Design: We subjected 223 archival primary melanomas to a horizontally integrated analysis of RNA expression, oncogenic mutations at 238 lesions, histomorphometry, and survival data. Results: Our previously described four-class structure that was elucidated in metastatic lesions was evident within the expression space of primary melanomas. Because these subclasses converged into two larger prognostic and phenotypic groups, we used the metastatic lesions to develop a binary subtype-based signature capable of distinguishing between “high” and “low” grade forms of the disease. The two-grade signature was subsequently applied to the primary melanomas. Compared with low-grade tumors, high-grade primary melanomas were significantly associated with increased tumor thickness, mitotic rate, ulceration (all P Conclusions: We provide evidence for a molecular organization within melanomas, which is preserved across all stages of disease. Clin Cancer Res; 18(15); 4026–36. ©2012 AACR .

Characterisation of amplification patterns and target genes at chromosome 11q13 in CCND1-amplified sporadic and familial breast tumours.

Abstract: Amplification of chromosomal region 11q13, containing the cell cycle regulatory gene CCND1, is frequently found in breast cancer and other malignancies. It is associated with the favourable oestrogen receptor (ER)-positive breast tumour phenotype, but also with poor prognosis and treatment failure. 11q13 spans almost 14 Mb and contains more than 200 genes and is affected by various patterns of copy number gains, suggesting complex mechanisms and selective pressure during tumour progression. In this study, we used 32 k tiling BAC array CGH to analyse 94 CCND1-amplified breast tumours from sporadic, hereditary, and familial breast cancers to fine map chromosome 11q13. A set containing 281 CCND1-non-amplified breast tumours was used for comparisons. We used gene expression data to further validate the functional effect of gene amplification. We identified six core regions covering 11q13.1-q14.1 that were amplified in different combinations. The major core contained CCND1, whereas two cores were found proximal of CCND1 and three distal. The majority of the CCND1-amplified tumours were ER-positive and classified as luminal B. Furthermore, we found that CCND1 amplification is associated with a more aggressive phenotype within histological grade 2 tumours and luminal A subtype tumours. Amplification was equally prevalent in familial and sporadic tumours, but strikingly rare in BRCA1- and BRCA2-mutated tumours. We conclude that 11q13 includes many potential target genes in addition to CCND1.

The Retinoblastoma Gene Undergoes Rearrangements in BRCA1-Deficient Basal-like Breast Cancer

Abstract: Breast tumors from BRCA1 germ line mutation carriers typically exhibit features of the basal-like molecular subtype. However, the specific genes recurrently mutated as a consequence of BRCA1 dysfunction have not been fully elucidated. In this study, we utilized gene expression profiling to molecularly subtype 577 breast tumors, including 72 breast tumors from BRCA1/2 mutation carriers. Focusing on the RB1 locus, we analyzed 33 BRCA1-mutated, 36 BRCA2-mutated and 48 non-BRCA1/2-mutated breast tumors using a custom-designed high-density oligomicroarray covering the RB1 gene. We found a strong association between the basal-like subtype and BRCA1-mutated breast tumors and the luminal B subtype and BRCA2-mutated breast tumors. RB1 was identified as a major target for genomic disruption in tumors arising in BRCA1 mutation carriers and in sporadic tumors with BRCA1 promoter-methylation, but rarely in other breast cancers. Homozygous deletions, intragenic breaks, or microdeletions were found in 33% of BRCA1-mutant tumors, 36% of BRCA1 promoter-methylated basal-like tumors, 13% of non-BRCA1 deficient basal-like tumors, and 3% of BRCA2-mutated tumors. In conclusion, RB1 was frequently inactivated by gross gene disruption in BRCA1-related hereditary breast cancer and BRCA1-methylated sporadic basal-like breast cancer, but rarely in BRCA2-hereditary breast cancer and non-BRCA1-deficient sporadic breast cancers. Together, our findings demonstrate the existence of genetic heterogeneity within the basal-like breast cancer subtype that is based upon BRCA1-status.