A patient is described with acute myelocytic leukemia refractory to conventional therapy, who also became highly resistant to methotrexate (MTX) after repeated courses of this drug. Leukemia cells from this patient were found to contain an elevated level of dihydrofolate reductase (DHFR) activity, with no change in the affinity of the enzyme for MTX. A sensitive "dot blot" assay revealed a fourfold increase in the gene copy number of DHFR. Southern blot analysis with a human DHFR cDNA probe confirmed this increase in the gene copy number, and demonstrated a similar restriction pattern with Eco R1, Hind III, and Pst 1 as seen with a highly amplified human leukemia cell line, K562. Additional DHFR fragments were detected, not seen in the K562 blot, suggesting the presence of pseudogenes, or a result of gene rearrangements occurring as part of the amplification process. Resistance to MTX in this patient was therefore ascribed to gene amplification and overproduction of DHFR.
Pharmacology, Toxicology and Pharmaceutical Science
1
11%
Nursing and Health Professions
1
11%
Earth and Planetary Sciences
1
11%
Other
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Unknown
1
11%
Attention Score in Context
Attention Score in Context
This research output has an Altmetric Attention Score of 3. This is our high-level measure of the quality and quantity of online attention that it has received. This Attention Score, as well as the ranking and number of research outputs shown below, was calculated when the research output was last mentioned on 06 November 2013.
All research outputs
#12,347,312
of 34,372,222 outputs
Outputs from Journal of Clinical Oncology
#20,086
of 32,344 outputs
Outputs of similar age
#10,514
of 48,394 outputs
Outputs of similar age from Journal of Clinical Oncology
#4
of 8 outputs
Altmetric has tracked 34,372,222 research outputs across all sources so far. This one is in the 38th percentile – i.e., 38% of other outputs scored the same or lower than it.
So far Altmetric has tracked 32,344 research outputs from this source. They typically receive a lot more attention than average, with a mean Attention Score of 20.4. This one is in the 17th percentile – i.e., 17% of its peers scored the same or lower than it.
Older research outputs will score higher simply because they've had more time to accumulate mentions. To account for age we can compare this Altmetric Attention Score to the 48,394 tracked outputs that were published within six weeks on either side of this one in any source. This one is in the 19th percentile – i.e., 19% of its contemporaries scored the same or lower than it.
We're also able to compare this research output to 8 others from the same source and published within six weeks on either side of this one. This one has scored higher than 4 of them.
