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A low-dose hypersensitive keratinocyte loss in response to fractionated radiotherapy is associated with growth arrest and apoptosis
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Oncology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Oncology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Oncology, Radiology and Clinical Immunology, Oncology.
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2010 (English)In: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 94, no 1, 90-101 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND AND PURPOSE: The existence of a hypersensitive radiation response to doses below 0.5Gy is well established for many normal and tumour cell lines. There is also evidence for hypersensitive tissue responses in acute skin damage and kidney function in mice. Recently, we have identified that a hypersensitive gammaH2AX response exists in human epidermis. The aim of this study was to investigate the dose-response of basal clonogenic keratinocytes in normal skin to fractionated radiotherapy with low dose fractions. MATERIALS: Skin punch biopsies were taken before and during radiotherapy from prostate cancer patients undergoing radiotherapy with a curative intent. Areas of epidermis receiving daily fractions of approximately 0.1, 0.2, 0.45 and 1.1Gy were biopsied on the same occasion to determine dose-response for each individual patient. In total, 89 cases were assessed either at 1, 2.5, 3, 4, 5 or 6.5 weeks in the treatment course. Biopsy sampling of another 25 patients was performed from areas receiving 0.45 and 1.1Gy per fraction at regular intervals throughout the 7-week treatment period. The number of basal keratinocytes per mm of the interfollicular epidermis was determined. The DNA damage response of the basal keratinocytes was investigated by immunohistochemical staining for molecular markers of growth arrest, mitosis and cell death, using p21, phospho-H3 and gammaH2AX, respectively. The number of stained keratinocytes in the basal layer was counted manually. The p21 staining was also quantified by digital image analysis. RESULTS: The individual dose-response relationships revealed a low-dose hypersensitivity for reduction of basal keratinocytes throughout 7 weeks of radiotherapy (p<0.01). Growth arrest and cell proliferation assessed at 1 week and 6.5 weeks showed, in both cases, hypersensitive increase of p21 (p<0.01) and hypersensitive depression of mitosis (p<0.01). Manual counting and digital image analysis of p21 showed good agreement. Cell death was infrequent but increased significantly between 1 and 6.5 weeks and displayed a hypersensitive dose-response at the end of the treatment period. CONCLUSIONS: A low-dose hypersensitivity in basal skin keratinocyte reduction is present throughout 7 weeks of radiotherapy. A persistent hypersensitive growth arrest response and cell killing mediate this effect.

Place, publisher, year, edition, pages
2010. Vol. 94, no 1, 90-101 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-134593DOI: 10.1016/j.radonc.2009.10.007ISI: 000274889900014PubMedID: 19931928OAI: oai:DiVA.org:uu-134593DiVA: diva2:372921
Available from: 2010-11-29 Created: 2010-11-29 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Quantification of Radiation Induced DNA Damage Response in Normal Skin Exposed in Clinical Settings
Open this publication in new window or tab >>Quantification of Radiation Induced DNA Damage Response in Normal Skin Exposed in Clinical Settings
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The structure, function and accessibility of epidermal skin provide aunique opportunity to study the DNA damage response (DDR) of a normaltissue. The in vivo response can be examined in detail, at a molecularlevel, and further associated to the structural changes, observed at atissue level. We collected an extensive skin biopsy material frompatients undergoing fractionated radiotherapy for 5 to 7 weeks. Several end-points inthe DDR pathways were examined before, during and after the treatment.

Quantification of DNA double strand break (DSB) signalling focirevealed a hypersensitivity to doses below 0.3Gy. Furthermore, aconsiderable amount of foci persisted between fractions. The low dosehypersensitivity was observed throughout the treatment and was alsoobserved for several key parameters further downstream in the DDR-pathway, such as p21-associated checkpoint activation, apoptosisinduction and reduction in basal keratinocyte density (BKD).Furthermore, for dose fractions above 1.0 Gy, a distinct acceleration inDDR was observed half way into treatment. This was manifested as anaccelerated loss of basal keratinocytes, mirrored by a simultaneousincrease in DSBs and p21 expression.

Quantifications of mitotic events revealed a pronounced suppression ofmitosis throughout the treatment which was clearly low dosehypersensitive. Thus, no evidence of accelerated repopulation could beobserved for fraction doses ranging from 0.05 to 2Gy.

Our results suggest that the keratinocyte response primarily isdetermined by checkpoints, which leads to pre-mitotic cell elimination by permanent growth arrest and apoptosis.

A comparison between the epidermal and dermal sub-compartments revealsa consistent up-regulation of the DDR response during treatment. Adifference was however observed in the recovery phase after treatment,where miR-34a and p21 remain up-regulated in dermis more persistentlythan in epidermis. Our observations suggest that the recovery phaseafter treatment can provide important clues to understand clinicalobservations such as the early and late effects observed in normaltissues during fractionated radiotherapy.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 51 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 631
Keyword
DNA damage response, low-dose hypersensitivity, dose response, normal tissue, epidermis, dermis, keratinocyte, fractionated radiotherapy, DNA double strand break, DSB, foci, gamma-H2AX, 53BP1, p21, checkpoint, apoptosis, mitosis, micro-RNA, miR-34a
National Category
Cancer and Oncology
Research subject
Oncology
Identifiers
urn:nbn:se:uu:diva-134600 (URN)978-91-554-7969-5 (ISBN)
Public defence
2011-01-14, Hörsal Betty Pettersson, Blåsenhus, von Kraemers Allé 1, Uppsala, 09:00 (English)
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Supervisors
Available from: 2010-12-23 Created: 2010-11-29 Last updated: 2011-01-13Bibliographically approved

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