The molecular classification of multiple myeloma

Area of Science:

• Oncology
• Genetics
• Molecular Biology

Background:

• Multiple myeloma (MM) is a hematologic malignancy characterized by the proliferation of plasma cells.
• Understanding the molecular heterogeneity of MM is crucial for developing targeted therapies and improving patient outcomes.

Purpose of the Study:

• To define the molecular subtypes of multiple myeloma (MM) using unsupervised hierarchic clustering of mRNA expression profiles.
• To correlate these molecular subtypes with genetic lesions, clinical features, and prognosis.

Main Methods:

• Unsupervised hierarchic clustering of mRNA expression profiles from CD138-enriched plasma cells of 414 newly diagnosed MM patients.
• Validation of identified disease subtypes based on known genetic lesions and gene signatures.
• Analysis of clinical features, including bone disease and relapse patterns, associated with each subtype.

Main Results:

• Seven validated MM subtypes were identified, strongly influenced by genetic lesions like c-MAF, MAFB, CCND1, CCND3, MMSET translocations, and hyperdiploidy.
• Common gene signatures were observed in subtypes with specific genetic activations (e.g., c-MAF/MAFB, CCND1/CCND3).
• A proliferation-associated gene signature was linked to disease progression and poor prognosis, dominating at relapse.
• Overexpression of genes on chromosome 1q characterized proliferation and MMSET-spike groups, associated with poor prognosis.
• A distinct subgroup with a myeloid gene expression signature showed favorable characteristics and prognosis.

Conclusions:

• Gene expression profiling reveals distinct molecular subtypes of multiple myeloma with varying clinical implications.
• The proliferation signature is a significant indicator of disease progression and poor prognosis in MM.
• Specific genetic lesions and chromosomal abnormalities define MM subtypes and influence patient outcomes.