Zinc-finger nucleases hone tumor cell
therapy
Engineering a patient’s own T cells to express tumor-targeting heterodimeric
T-cell receptors (TCRs) is a promising therapeutic strategy.
Even so, development of this method has been undermined by
unintended dimerization of endogenous and exogenous TCR chains,
resulting in hybrid receptors that lead to off-target effects and autoimmunity,
and by suboptimal expression of the introduced tumor-specific
TCR. Provasi et al. overcome these obstacles by first disrupting
the endogenous TCR a and b chains using zinc-finger nucleases.
Subsequent expression of tumor-targeting TCR chains delivered by
lentiviral vectors produced high levels of expression of the expected
antigen-specific TCRs. Tested in a series of experimental mouse models,
the engineered cells did not set off an auto-immune response
and protected the mice against leukemia. (Nat. Med. advance online
publication, doi:10.1038/nm.2700, 1 April 2012) JK
Drug lead for osteoarthritis
Osteoarthritis occurs when synovial joints fail. Drugs that alter
the course of this disease, rather than simply alleviate symptoms,
are in clinical trials, but none have been approved yet in the
United States or the European Union. Johnson et al. describe the
discovery and characterization of a small molecule, kartogenin,
that improves joint function and promotes the regeneration of
cartilage in vivo in two rodent models of chronic and acute joint
injury. In vitro experiments indicated that kartogenin induces
the differentiation of mesenchymal stem cells into cartilage cells
(chondrocytes) and protects existing chondrocytes under pathophysiological
conditions. The authors found that kartogenin binds
filamin A, a protein that crosslinks actin filaments, through which
it regulates the nuclear localization of a transcription factor complex
of CBFb and RUNX2. Knockdown of either CBFb or RUNX2
with short-hairpin RNAs blocked the effect of kartogenin on cellular
differentiation. Kartogenin is the first drug reported to target
filamin A and as such may complement other osteoarthritis
drugs under development. (Science published online, doi:10.1126/
science.1215157, 5 April 2012) CM
Pharmacogenomic profiling of cancer
drugs
Most cancer drugs are effective in only a fraction of the patients who
take them. If this responsive subset could be identified in advance,
patients would be spared useless, cytotoxic treatments, and the regulatory
pathway for new agents would be simplified. For a handful
of drugs, efficacy is known to track closely with the presence of
particular mutations, but, overall, the use of tumor genotype data
to predict optimal drug regimens is still at an early stage. Two new
reports have addressed this problem by pharmacological screening
on human cancer cell lines at a larger scale than has been carried out
previously. Garnett et al. tested 130 drugs on 639 cell lines, whereas
Barretina et al. collected sequence, chromosomal copy number and
transcriptional data on 947 cell lines and measured the activity of 24
drugs on 479 of these lines. Both studies uncovered known markers
of drug sensitivity as well as novel candidate markers. Moreover,
established correlations between drug efficacy and genotype were
found to be invalid in some cases. (Nature 483, 570–575 and 603–
607, 2012)