Research
Using transcriptomics to identify and validate novel biomarkers of human skeletal muscle cancer cachexia
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* Corresponding authors: Iain J Gallagher iaingallagher@ed.ac.uk - James A Timmons Jamie.Timmons@gmail.com
- † Equal contributors
Genome Medicine 2010, 2:1 doi:10.1186/gm122
Role of ubiquitin-proteasome in cancer cachexia
Maurizio Bossola (2010-03-17 09:36) Catholic University
Sir,
we read with much interest the article by Sthepens et al recently published in Genome
Medicine (1) that shows, among other results, that the mRNA expression of the E3 ligases
MURF1 and MAFbx, examined by qRT-PCR, was not related with weight loss in the skeletal
muscle of patients with cancer of the upper gastrointestinal tract. According to the
authors, this result would suggest that the ubiquitin E3 ligases do not play the same
role in human cancer cachexia as that previously demonstrated in animal and cell studies
and that any support to the findings of previous human studies (2-4) could be found.
Indeed, few studies have investigated the ubiquitin-proteasome pathway in the skeletal
muscle of cancer patients (2-5), but none of these have assessed the expression of
E3 ligases. In our first study (2), northern blot analysis of the skeletal muscle
revealed a significant twofold increase of the mRNA levels for ubiquitin in gastric
cancer patients with respect to control subjects. The levels of ubiquitin mRNA did
not correlate with age, BMI, percent weight loss, serum albumin and total lymphocyte
count but were higher in stage IV than in stages I-II-III. In a second study (3),
we found that the three proteasome activities (chymotrypsin-like; trypsin-like and
peptidyl-glutamyl-peptidase) significantly increased in the skeletal muscle of gastric
cancer patients with respect to controls and that advanced tumor stage, poor nutritional
status, and age more than 50 years were associated with significantly higher chymotrypsin-like
activity but had no influence on trypsin-like and peptidyl-glutamyl-peptidase. The
results of the study of Khal et al (4) demonstrated that the expression of mRNA for
proteasome subunits C2 and C5 was three to five times higher in cancer patients with
weight loss than in control subjects. It seems that an increased expression and activity
of the ubiquitin-proteasome proteolytic pathway occurs in cancer patients when compared
with controls who are not affected by comorbidities. Thus, it could be interesting
to know if, in the study of Stephens et al, there were differences between cancer
patients and controls in the expression of E3 ligases, although we are aware that
the controls were few and significantly younger. It remains that the role of the
ubiquitin-proteasome pathway in skeletal muscle of cancer patients suffering weight
loss and/or cachexia needs to be further investigated and elucidated.
1. Stephens NA, Gallagher IJ, Rooyackers O, Skipworth RJ, Tan BH, Marstrand T, Ross
JA, Guttridge DC, Lundell L, Fearon KC, Timmons JA. . Using transcriptomics to identify
and validate novel biomarkers of human skeletal muscle cancer cachexia. Genome Med.
2010;2:1-12
2. Bossola M, Muscaritoli M, Costelli P, Grieco G, Bonelli G, Pacelli F, Rossi Fanelli
F, Doglietto GB, Baccino FM. Increased muscle proteasome activity correlates with
disease severity in gastric cancer patients. Ann Surg. 2003;237:384-389.
3. Bossola M, Muscaritoli M, Costelli P, Bellantone R, Pacelli F, Busquets S, Argilès
J, Lopez-Soriano FJ, Civello IM, Baccino FM, Rossi Fanelli F, Doglietto GB. Increased
muscle ubiquitin mRNA levels in gastric cancer patients. Am J Physiol Regul Integr
Comp Physiol. 2001;280:R1518-23
4. Greenhaff PL, Karagounis LG, Peirce N, Simpson EJ, Hazell M, Layfield R, Wackerhage
H, Smith K, Atherton P, Selby A, Rennie MJ. Disassociation between the effects of
amino acids and insulin on signaling, ubiquitin ligases, and protein turnover in human
muscle. Am J Physiol Endocrinol Metab. 2008;295:E595¿604.
5. Jagoe RT, Redfern CP, Roberts RG, Gibson GJ, Goodship TH. Skeletal muscle mRNA
levels for cathepsin B, but not components of the ubiquitin-proteasome pathway, are
increased in patients with lung cancer referred for thoracotomy. Clin Sci (Lond).
2002;102:353¿361
Competing interests
None declared
sample sizes
James Timmons (2010-04-19 10:29) Royal Veterinary College
I would like to thank Dr Bossola for their interesting comments. When studies using the same approach we did find strong evidence that ICU patients - patients with severe imobillity and inflammation - that the pathways mentioned by Dr Bossola were indeed activated as described. In contrast, using the same technology we did not find such pathways activated in this type of cancer related cachexia (Frederikson et al PLos One 2008). Thus we know the technology is valid.
Many molecular profiling studies in patients versus controls often use only a handful of patients. This has led to great confusion in the diabetes field, for example, with respect to gene changes in muscle insulin resistance. The same is true of cancer cachexia. the majority of studies using molecular profiling have relied on only small case-contorl sample sizes.
In our present study we utilise the relationship between modest and severe weight loss and not simply a case control analysis. Further, the sample size far exceeds previous studies and we profile 3 distinct muscle groups in humans, across two clinical centres, to find common mechanisms. I believe these reasons may explain the differences in the studies mentioned in the points made by Dr Bossola.
Competing interests
I am an author of the article discussed by Dr Bossola .
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