M. Ataka et al.

Table 1. Topoisomerase I expression and clinicopathological findings
Number of Topoisomerase I
patients
Negative Positive
Location of tumor		
Histopathology		
Dukes’ classification		

Colon
Rectum
Well-differentiated type
Moderately or poorly differentiated type
A or B
C

55
49
54
50
4163

2930
39
20
2930

26
191530
1233

P
0.383
0.001
0.020

patients with colorectal cancer or not, variables(histological type, Dukes’ classification, Topo I
protein expression) were analyzed by Cox’s proportional hazards regression model. Analysis
determined that Topo I protein expression was not
a prognostic factor independent from Dukes’ classification (Table 2).

Correlation with Topo I protein expression
and clinicopathological findings of patients
Topo I protein expression was detected in 45 of104 patients (43.2%). Topo I protein expression
was more frequently detected in moderately differentiated type or poorly differentiated type
colorectal carcinoma than in well-differentiatedcarcinoma (Table 1). Moreover, Topo I was positive in only 12 of 41 patients (29.3%) in Dukes’
A and B, while in 33 of 63 patients (52.4%) inDukes’ C (Table 1).

Topo I protein expression of tumors and effectiveness of adjuvant chemotherapy inpatients with Dukes’ C carcinoma
Out of the 63 Dukes’ C patients, 47 were treatedwith 5-fluorouracil-based chemotherapy postoperatively. An oral dose of 600 mg/day of
1-(2-tetrahydrofuryl)-5-fluorouracil/uracil (1:4)(UFT; Taiho Pharmaceutical, Tokushima, Japan)
was administered to these patients for at least 1year. Postoperative chemotherapy was not performed on 13 patients because of advanced age

Topo I protein expression and prognosis ofpatients
The overall and disease-free 5-year survival ratesof 104 patients with colorectal cancer were 64.9%
and 75.5%, respectively. The disease-free 5-year
survival rate of 50 patients with moderately differentiated or poorly differentiated carcinoma(63.6%) was lower than that of 54 patients withwell differentiated carcinoma (86.4%, P = 0.01).
And the disease-free 5-year survival rate of 63 patients in Dukes’ C (64.4%) was lower than that of
41 patients in Dukes’ A and B (94.3%, P = 0.002).
Moreover, when the 104 patients were dividedinto two sub-groups according to their immunohistochemical findings, the disease-free 5-year
survival rate of the 45 Topo I-positive patients(62.7%) was significantly lower than that of the 59
Topo I-negative patients (84.3%, P = 0.005, Fig. 3).
In order to understand whether Topo I protein expression is one of the prognostic factors ofFig. 3. The disease-free 5-year survival curve of 45
topoisomerase I (Topo I)-positive patients (dotted line)
is significantly lower than that of 59 Topo I-negative patients (solid line) (P = 0.005). [ ], number of patients.

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Topo I expression in colorectal cancer

Table 2. Multivariate survival analysis in patients with colorectal cancer
Variable

Hazard ratio

95% Confidential interval

P

1.379

0.548– 3.467

0.495

3.822

1.307–14.09

0.044

2.007

0.908– 4.937

0.083

Histological type of tumors
Moderately and poorly differentiated types
versus well-differentiated types
Dukes’ classification
C versus A and B
Topoisomerase I protein expression
Positive versus negative(over 75) and 3 patients refused postoperative
chemotherapy. At the end of 2006, 23 Dukes’
C patients died from cancer recurrence. Fifteen
were in the chemotherapy group (32%, 15/47)
and 8 were in the non-chemotherapy group (50%,8/16). Thus, 5-fluorouracil-based postoperative
chemotherapy reduced the percentage of cancer
recurrence from 50% to 32% in Dukes’ C patients(P = 0.2).
Among the 23 Dukes’ C patients who diedfrom cancer recurrence, 16 were treated with
Topo I inhibitor (CPT-11) just after detection of
the recurrence. We observed that among the 16,
12 had Topo I-positive primary tumors, while 4
had Topo I-negative primary tumors. The survival periods just after the start of CPT-11 chemotherapy ranged from 2 to 43 months. Of these16 patients, CPT-11 chemotherapy prolonged thesurvival of 12 patients who had Topo I-positive
primary tumors over the 4 patients who had TopoI-negative primary tumors (Table 3).

Discussion
It is known that Topo I expression is not observed in normal colon tissue, but we found TopoI-positive cells in basal cell layer of normal skinadjacent to rectal cancer. Bauman et al. (1997)and Hafian et al. (2004) reported that the expression of Topo I and Topo II protein were detectedin normal tissue with proliferating cells including
normal tonsil and normal skin. So, closed correlation between Topo I protein expression and cellproliferative activity is thought to be possible. In
this study, we demonstrated the frequent occurrence of Topo I expression in surgically resectedcolorectal cancer (43.2%). We found that thepercentage of patients who had Topo I-positive tumors was much higher in Dukes’ C than in Dukes’
A and B. Moreover, Topo I protein expression was
more frequently detected in moderately or poorly
differentiated adenocarcinomas than in well differentiated carcinomas. These findings indicate that
Topo I expression closely correlated with tumor
progression and histopathological differentiationin colorectal cancer. Also in human sarcomas, theincidence of detectable Topo I protein expression
increased with tumor progression (Caleman et al.,2002). However, Staley et al. (1999) reported nocorrelation between Topo I expression and Dukes’
classification in 29 patients with colorectal cancer.
But the number of patients in their study was too
small to elucidate a clear correlation between TopoI protein expression and tumor progression incolorectal cancer. Further investigation is needed.

Table 3. Survival time just after starting CPT-11
chemotherapy in 16 patients with recurrent
colorectal cancer		
50%
Number Survivalof
period†patients (month)Topoisomerase I-negative
Topoisomerase I-positive

4124
12P
0.041

† After starting chemotherapy.

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M. Ataka et al.

We found that the 5-fluorouracil-based postoperative chemotherapy prolonged the survival ofpatients with Dukes’ C colorectal cancer insteadof Topo I protein expression of tumors. Recently,
Topo I inhibitors have frequently been used in
the treatment of advanced or recurrent colorectal
cancers (Paradiso et al., 2004). But correlation
between clinical effectiveness of Topo I inhibitors
and tumor expression of Topo I protein has notbeen well studied in human colorectal cancer patients. In our study, we found that when CPT-11
chemotherapy had been used for patients withrecurrent tumors, the survival periods of patients
who had Topo I-positive primary tumors weresignificantly prolonged than those of patients who
had Topo I-negative primary tumors. In vitro, it
has been shown that tumors with a higher level ofTopo I protein responded to Topo I inhibitors, but
RNA expression was not predictive for the antiproliferative effect of Topo I inhibitors (Mcleodet al., 1996; Jansen et al., 1997). However, ATPbinding cassette transporters called ABCG2 orcarboxilesterases have been reported to correlatewith tumor sensitivity against Topo I inhibitors(Pavillard et al., 2002; Sanghani et al., 2003; Wierdl et al., 2003; Candeil et al., 2004). In order toprolong the survival of patients with advanced orrecurrent colorectal cancer or to prevent ineffective chemotherapy for such patients, clinical importance of Topo I protein expression in colorectal cancer, especially sensitivity of tumors to TopoI inhibitors, should be investigated extensively.

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Received August 24, 2007; accepted September 20, 2007
Corresponding author: Masahide Ikeguchi, MD

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