Abstract
Enzymatic activation of irinotecan (CPT-11) is due to carboxylesterase (CES), and its pharmacological behavior is influenced by drug resistance-related proteins. We previously reported that the clinical response and prognosis of metastatic colorectal cancer (mCRC) patients did not differ in tumors with different thymidylate synthase (TS) or topoisomerase-I (Topo-I) expression. Using immunohistochemistry (IHC), we evaluated the biological role of CES2 and the expression of breast cancer resistance protein (BCRP/ABCG2) in 58 consecutive mCRC patients, who had undergone a first-line CPT-11/5-FU/leucovirin (FOLFIRI) regimen. The expression of these proteins was also examined in a group of synchronous lymph nodes and liver metastases. Furthermore, all samples were revaluated for TS and Topo-I expression. High expression of CES2, ABCG2, TS and Topo-I was observed in 55%, 56%, 38% and 49% of patients, respectively. There was a significant association between high TS and high ABCG2 expression (p = 0.049). Univariate analysis showed that only TS expression significantly impacted on time to progression (p = 0.005). Moreover, Cox’ multivariate analysis revealed that TS expression was significantly associated with overall survival (p = 0.01). No significant correlation was found between investigated markers expression and clinical response. Topo-I expression resulted in being significantly higher in liver metastases with respect to the corresponding primary tumors (p < 0.0001), emphasizing the role of Topo-I expression in metastatic cancer biology. In primary tumor tissues, CES2 expression tended to be higher than that observed in liver metastasis tissues (p = 0.05). These preliminary data may suggest CES2 over-expression as a potential marker of malignant phenotype. In light of these findings, we suggest that Topo-I expression together with TS expression could be associated with metastatic progression of CRC. Further studies are warranted with the aim of evaluating the potential predictive and prognostic role of CES2 and ABCG2 in larger series of patients.
Highlights
IntroductionIrinotecan (CPT-11) belongs to the camptothecin class of topoisomerase I (Topo-I) inhibitors [1]
Irinotecan (CPT-11) belongs to the camptothecin class of topoisomerase I (Topo-I) inhibitors [1].It is activated by 7-ethyl-10-hydroxy-camptothecin (SN-38), which is approximately 100- to 1000-fold more cytotoxic than the parent drug
We examined the subcellular expression of carboxylesterase 2 (CES2) and ABCG2 by immunohistochemistry in a well-selected consecutive series of metastatic colorectal cancer (mCRC) patients treated with the FOLFIRI regimen and investigated their relation to clinical outcome
Summary
Irinotecan (CPT-11) belongs to the camptothecin class of topoisomerase I (Topo-I) inhibitors [1]. It is activated by 7-ethyl-10-hydroxy-camptothecin (SN-38), which is approximately 100- to 1000-fold more cytotoxic than the parent drug. Mechanisms of resistance to CPT-11 have been identified as decreased Topo-I levels, reduced drug activation via carboxylesterase 2 (CES2) and increased efflux of CPT-11 and SN38 out of the cell by ATP-binding cassette (ABC) transporters [3]. Expression of drug pathway proteins is independent of tumor type. Few data are available on the relative expression of these proteins in CRC [4,5,6]
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