How germline genes promote malignancy in cancer cells

Abstract

Cancers often express hundreds of genes otherwise specific to germ cells, the germline/cancer (GC) genes. Here, we present and discuss the hypothesis that activation of a "germline program" promotes cancer cell malignancy. We do so by proposing four hallmark processes of the germline: meiosis, epigenetic plasticity, migration, and metabolic plasticity. Together, these hallmarks enable replicative immortality of germ cells as well as cancer cells. Especially meiotic genes are frequently expressed in cancer, implying that genes unique to meiosis may play a role in oncogenesis. Because GC genes are not expressed in healthy somatic tissues, they form an appealing source of specific treatment targets with limited side effects besides infertility. Although it is still unclear why germ cell specific genes are so abundantly expressed in cancer, from our hypothesis it follows that the germline's reproductive program is intrinsic to cancer development.

Higher Expression Levels of SSX1 and SSX2 in Patients with Colon Cancer: Regulated In Vitro by the Inhibition of Methylation and Histone Deacetylation

“…The current classification approach for CT genes was developed by Hoffman et al [ 8 ]. On the basis of an in silico pipeline, a subgroup of human meiotic genes was described as being composed of CT genes and presented a highly restricted cancer-specific marker [ 20 , 22 ].…”

A novel cancer-germline gene DAZL promotes progression and cisplatin resistance of non-small cell lung cancer by upregulating JAK2 and MCM8

“…Cancer cells usually express some germline genes known as cancer/germline (CG) or cancer/testis genes [7]. Under normal physiological conditions, CG genes are predominantly expressed in germ cells of adult testes and fetal ovaries, but they are aberrantly expressed in various cancers [8].…”

Somatic cancers: Hijacking germ cell immortality tools

“…[4] Bruggeman et al developed this idea into a more comprehensive induction of germline programme in somatic cancer cells that encompasses not only the activation of meiotic genes and epigenetic instability but also metabolic plasticity and propensity to invasion, which can be linked to embryonic migration of primordial germ cells. [1] The idea of the preferential germline-like transformation of somatic cancer cells contrasts with another currently discussed hypothesis stipulating that hypomethylated and 'unstable' chromatin promotes stochastic gene expression changes leading to its 'aggressiveness ' , increasing malignancy and spread of the tumour. [5] Bruggeman et al are experts in germ cell biology, hence, they argue eloquently for a non-random activation of meiotic genes in cancer, and provide a great deal of supporting evidence from their own bioinformatic analysis of hallmark germline features in several somatic cancers.…”

“…[5] Bruggeman et al are experts in germ cell biology, hence, they argue eloquently for a non-random activation of meiotic genes in cancer, and provide a great deal of supporting evidence from their own bioinformatic analysis of hallmark germline features in several somatic cancers. [1] The jury is still out which of the two concepts is most plausible, and detailed mechanistic studies of cancer cells in humans and other species are needed to establish which events -genomic rearrangements linked to induction of meiosis -or rather epigenetic adaptation -are the first events triggering malignant transformation of somatic cells.…”

“…This similarity is the topic of the ‘Hypothesis’ article in this issue of BioEssays , written by Bruggeman and colleagues. [ 1 ] The authors propose that malignancy is promoted primarily by the activation of a ‘germline programme’. This concept is not entirely new, as others have previously noticed germ cell features in somatic tumours.…”