Telomeres, telomerase and colorectal cancer

Table 2 Telomere lengths and colorectal cancer

Ref.	Cases	Main findings
Hastie et al[31], 1990	23 (20 CRCs, 3 adenomas) and patient-matched non-cancerous mucosa (frozen samples)	TL
		Decrease with age in non-cancerous cells (33 bp per year)
		Shorter in CRCs and adenomas than in normal mucosa
Engelhardt et al[32], 1997	80 (50 CRCs, 20 polyps, 10 colitis) and CRC patient-matched non-cancerous mucosa (frozen samples)	TL
		Shorter in CRCs than in normal mucosa
		Shorter in CRCs than in polyps and colitis
		Longer in late-stage cancer with higher telomerase activity
		Do not differ between colon and rectum cancer
Takagi et al[33], 1999	61 CRC (including 12 non-ulcerating and 39 ulcerating tumours, according to Borrmann's classification) and patient-matched non-cancerous mucosa (frozen samples)	TL
		Shorter in non-ulcerating CRCs than in normal mucosa
		Shorter in non-ulcerating than in ulcerating tumours
		Not correlated with tumour stage or grade
		Not correlated with telomerase activity
Katayama et al[34], 1999	35 (26 CRCs, 9 polyps) (frozen samples)	TL
		Do not differ between CRCs and polyps
Nakamura et al[35], 2000	124 CRC and patient-matched non-cancerous mucosa (frozen samples)	TL
		Shorter in CRCs than in normal mucosa
		Decrease with age in both cancer and non-cancerous cells (44 and 50 bp/yr)
Plentz et al[36], 2003	10 (adenoma-carcinoma transition) (paraffin-embedded samples)	TL
		Shorter in high-grade dysplastic areas than in the surrounding adenoma
Gertler et al[37], 2004	57 CRC and patient-matched non-cancerous mucosa (frozen samples)	TL
		Shorter in CRCs than in adjacent mucosa
		Decrease with age only in non-cancer cells (19 bp per year)
		Correlate with tumour stage, being longer in advanced tumours
		Correlate with TERT mRNA levels
		Lead to a poor prognosis if TL cancer/TL non-cancer > 0.9
		Do not differ between colon and rectum cancer
Garcia-Aranda et al[38], 2006	91 CRC (23 right-colon, 13 left-colon, 55 rectum) and patient-matched non-cancerous mucosa (frozen samples)	TL
		Shorter in CRC than in adjacent mucosa
		Shorter in right-colon cancers than in tumours located in other sites
		Shorter in poorly differentiated tumours
		Tend to be longer in telomerase-positive CRCs
		Have prognostic value (longer telomeres: poor clinical outcome)
		Correlated with the expression of TRF1 protein
O’Sullivan et al[39], 2006	38 (26 adenomas, 12 CRCs) (paraffin-embedded samples)	TL
		Shorter in adenomas than in adjacent and distant mucosa
		Similar in CRCs and adjacent and distant mucosa
Raynaud et al[40], 2008	15, each case with normal mucosa, low-grade dysplasia, high-grade dysplasia and carcinoma (paraffin-embedded samples)	TL
		Shorter in low-grade and high-grade dysplasia than in carcinoma
		Inversely correlated with activation of the DDR pathway
Rampazzo et al[41], 2010	118 CRC (53 right-colon, 30 left-colon, 35 rectum) and patient-matched non-cancerous mucosa (frozen samples)	TL
		Shorter in CRCs than in adjacent mucosa
		Shorter in right-colon cancers than in tumours located in other sites
		Shorter in MSI than in MSS tumours
		Decrease with age only in non-cancer cells
		Not correlated with tumour stage or grade
		Not correlated with TERT mRNA levels
Valls et al[42], 2011	147 CRC and patient-matched non-cancerous mucosa (frozen samples)	TL
		Shorter in CRCs than in adjacent mucosa
		In cancer correlate with TL in normal mucosa
		Do not differ between colon and rectum cancer
		Not correlated with tumor stage
		Have prognostic value (TL cancer/TL non-cancer ≤ 1: higher OS)
Roger et al[43], 2013	135 (85 polyps from 10 patients with FAP, 50 CRCs) (frozen samples)	TL
		Shorter in polyps than in normal mucosa
		Correlated with genomic rearrangement in polyps
		Independent of adenoma size
		In polyps may reflect the TL of the originating cells

TL: Telomere lengths; CRC: Colorectal cancer; DDR: DNA damage response; OS: Overall survival; FAP: Familial adenomatous polyposis.