What is 1p/19q codeletion?

The topic of “1p/19q codeletion” is covered under following subheadings:

Introduction and Important Points #

  • Genetic marker for Oligodendrogliomas (pathognomonic for oligodendroglioma)
  • Tie-breaker’ to distinquish oligo- from astrocytomas
  • It indicates favorable prognosis
  • It is associated with better chemosensitivity (increased response to chemotherapy)
  • It is due to Loss of one arm of a hybrid chromosome is called loss of heterozygosity (LOH)
  • This is tested using FISH (fluorescence in situ hybridization)
1p 19q codeletion

What is the Incidence of 1p/19q codeletion in Oligodendrogliomas? #

  • Codeletion of 1p and 19q occurs in up to 70% of oligodendrogliomas. [2] [3]
  • This genetic signature was first noted by Reifenberger et al [5]

How is it detected? #

  • Chromosome 1p/19q codeletion is demonstrated by fluorescence in situ hybridization (FISH) [1]
  • Demonstration of 1p/19q codeletion in addition to demonstration of IDH mutation, is now necessary for the diagnosis of oligodendroglioma,
  • FISH probes do not directly demonstrate complete deletion of the entire arms of chromosomes
  • Thus, alternative molecular testing methods that probe copy number changes along entire chromosomes (gene chip arrays for example) are preferred and will limit false positive results

Clinical Significance #

Gliomas that have lost the entire short arm of chromosome 1 (1p) and the entire long-arm of chromosome 19 (19q), have 2 distinct prognostic features [4]:

  1. they grow slowly, even those that are anaplastic,
  2. they respond to DNA damaging therapies

Acknowledgement

Article Written By: Dr Sandeep Moolchandani MS, MHA, DrNB Neurosurgery

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References

  1. Ferris, Sean P.; Hofmann, Jeffrey W.; Solomon, David A.; Perry, Arie (2017). Characterization of gliomas: from morphology to molecules. Virchows Archiv, (), –. doi:10.1007/s00428-017-2181-4 
  2. Jenkins RB, Blair H, Ballman KV, et al. A t(1;19)(q10;p10) mediates the combined deletions of 1p and 19q and predicts a better prognosis of patients with oligodendroglioma. Cancer Res. 2006;66:9852–9861
  3. Griffin CA, Burger P, Morsberger L, et al. Identification of der(1; 19)(q10;p10) in five oligodendrogliomas suggests mechanism of concurrent 1p and 19q loss. J Neuropathol Exp Neurol. 2006;65:988 –994.
  4. Cairncross, Gregory; Jenkins, Robert (2008). Gliomas With 1p/19q Codeletion:a.k.a. Oligodendroglioma. The Cancer Journal, 14(6), 352–357. doi:10.1097/ppo.0b013e31818d8178
  5. Reinfenberger J, Reinfenberger G, Liu L, et al. Molecular genetic analysis of oligodendroglial tumors shows preferential allelic deletions on 10q and 1p. Am J Pathol. 1994;145:1175–1190

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