In Nature Reviews Cancer this week, Darren Burgess says genomic analysis of cancer is making researchers aware of how genetically complex and heterogeneous cancer is. Two recent studies published in Nature — one of which is discussed in more detail at our sister publication, Genome Technology — reveal that even the subpopulations of cells that initiate leukemia in patients are surprisingly heterogeneous. "Acute lymphoblastic leukaemia is particularly amenable to studies of genetic subpopulations owing to the ease of single-cell analyses, its limited genomic instability and its variety of well-characterized, recurrent mutations," Burgess says. "Another key question is whether the extent of genetic complexity seen for ALL-initiating cells will be mirrored in other cancers."
Also in Nature Reviews Cancer this week, Nicola McCarthy says that researchers need to work on finding how expression of the protein CD44 is connected to cancer stem cells. McCarthy says a recent article in Nature shows that CD44 is a target of microRNA miR-34a, which indicates that there may be a role for CD44 in cancer stem cell activity in prostate cancer. "Expression of miR-34a induces cell cycle arrest or senescence and is regulated by p53," McCarthy says. "Increasing the expression of miR-34a in human prostate cancer cells induced senescence, apoptosis or cell cycle arrest independently of the mutation status of p53 and suppressed the growth of various prostate cancer cells in non-obese diabetic–severe combined immunodeficient mice." MiR-34a is known to inhibit tumor growth, and that action was also seen in cancer stem cells expressing CD44, she adds, meaning, "CD44, a protein known to have many functions in cell biology, including the promotion of invasive growth, seems to be a key target for the miR-34a-mediated inhibition of prostate tumour progression."
And published online in advance this week, a team of researchers from Australia and China says that "corruption of chromosome cohesin" could lead to cancer. Cohesin is a complex protein with many different cellular roles, and it contributes to DNA damage response and chromatin regulation. Much has been known about cohesin's role in a physiological context, but emerging research shows it may also have an impact on tumor initiation or progression, the authors write.