Type I collagen turnover and cross-linking are increased in irradiated skin of breast cancer patients.
OBJECTIVE
The effects of radiation therapy on the turnover and structure of type I collagen were studied in irradiated and contralateral skin of 18 breast cancer patients without clinically evident fibrosis.


METHODS
The rates of on-going type I collagen synthesis and degradation were assessed by the aminoterminal propeptide of type I procollagen (PINP) and by two different assays (ICTP and SP4) for the carboxyterminal telopeptide of type I collagen in the soluble tissue extracts, respectively. Also, TIMP-1, TIMP-2 and the MMP-2/TIMP-2 complex were measured in the tissue extracts. Insoluble skin matrices, containing the cross-linked type I collagen fibres, were heat-denatured and digested with trypsin. Then, the variants of the carboxyterminal telopeptide of type I collagen were separated by high performance liquid chromatography (HPLC). The major histidinohydroxylysinonorleucine (HHL)-cross-linked variant was quantified by the SP4 assay, and the minor pyridinoline analogue (PA)-cross-linked telopeptide was quantified by the ICTP assay.


RESULTS
Both the synthesis and degradation of type I collagen were increased (r=0.906; P<0.001) on the irradiated side, whereas the concentration of the MMP-2/TIMP-2 complex was decreased. In the insoluble tissue digests, the HHL-cross-linked telopeptides of type I collagen, also, when expressed/tissue hydroxyproline, were increased in the irradiated skin. TIMP-1, TIMP-2 or PA-cross-linked telopeptides of type I collagen showed no differences between the two sides.


CONCLUSIONS
Radiotherapy induces a long-term increase in the turnover of type I collagen and leads to the accumulation of cross-linked type I collagen in skin.
Sassi
M
M
Department of Clinical Chemistry, University of Oulu, POB 5000, 90014 Oulu, Finland.
Jukkola
A
A
Riekki
R
R
Höyhtyä
M
M
Risteli
L
L
Oikarinen
A
A
Risteli
J
J
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000532:radiotherapy*; D003094:Collagen / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D024042:Collagen Type I; D004151:Dipeptides / Q000032:analysis; D005260:Female; D006639:Histidine / Q000031:analogs & derivatives* / Q000032:analysis; D006801:Humans; D020782:Matrix Metalloproteinases / Q000032:analysis; D008875:Middle Aged; D010446:Peptide Fragments / Q000032:analysis; D010455:Peptides / Q000032:analysis; D011347:Procollagen / Q000032:analysis; D012867:Skin / Q000378:metabolism / Q000528:radiation effects*; D019714:Tissue Inhibitor of Metalloproteinases / Q000032:analysis
D024042:Collagen Type I; D004151:Dipeptides; D010446:Peptide Fragments; D010455:Peptides; D011347:Procollagen; D019714:Tissue Inhibitor of Metalloproteinases; C052929:collagen type I trimeric cross-linked peptide; C075793:histidinohydroxylysinonorleucine; C047202:procollagen Type I N-terminal peptide; D006639:Histidine; D003094:Collagen; D020782:Matrix Metalloproteinases