Myeloma is a type of cancer affecting B-cells. B-cells are immune system cells that are made in the bone marrow and produce antibodies (immunoglobulins) to fight infections. Myeloma cells are transformed, activated B-cells that are malignant.

How do normal B-cells become malignant?

Normal B-cells produce specific antibodies that recognize foreign pathogens such as bacteria or viruses. The majority of B-cells have a finite life span that ranges from a month to a few months, after which they undergo a process called apoptosis, or programmed cell death. Small subsets of normal B-cells called memory B-cells live longer, lasting several years or even decades. These are necessary to launch a quick response to a second infection by the same pathogen.

Myeloma cells have acquired mutations or undergone chromosomal alterations as a result of exposure to toxic chemicals, radiation, viral infections, or immune disorders.

Genetic mutations that cause myeloma

Mutations in critical oncogenes or tumor suppressor genes in B-cells can cause myeloma.

Oncogenes are genes that have the potential to cause cancer. Mutations in these genes can cause them to become overactive, leading cells to grow out of control and survive beyond their normal lifespans.

Tumor suppressor genes are responsible for controlling or suppressing cell growth and triggering apoptosis. Mutations in these genes that cause them to be underactive can lead to cancer.

Other genetic alterations commonly observed in myeloma are:

  • Duplications resulting in multiple copies of a gene or a chromosomal segment
  • Deletions in which a chromosomal segment or gene is missing
  • Translocations in which part of a chromosome gets incorporated into a different chromosome or to a new site on the same chromosome

Duplications and translocation of chromosome 1 segments have been reported in myeloma patients.

Common translocations seen in patients with myeloma include those between chromosome 14 and chromosome 4, 6, 11, 16, or 20.

Deletions in chromosomes 1, 13, and 17 have also been reported in myeloma cells from various patients.

In all these cases, chromosomal alterations that result in switching on an oncogene or switching off a tumor suppressor gene cause myeloma.

Risk factors associated with myeloma

Several factors are associated with a greater risk of developing myeloma. These include:

 

Last updated: March 3, 2020

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