Rosario Sanguedolce

Difference in Ki67 and Thymidylate Synthase Expression in Primary Tumour Compared with Metastatic Nodes in Breast Cancer Patients

Breast cancer is a heterogeneous disease, so therapeutic predictive biological markers need to be identified. To date an accurate evaluation of predictive markers is mainly done at the primary site; however, the main goal of adjuvant therapy for breast cancer is the control of micrometastases. The aim of this study is to assess as therapeutic and/or prognostic marker, the proliferation status of primary tumors and involved nodes as measured by Ki67 and thymidylate synthase (TS) expression, in 30 breast cancer node positive patients. TS is the main target of 5-fluorouracil (5-FU) activity, and its overexpression is one of the mechanisms of 5-FU drug resistance; however, in some studies its absence is responsible for a worse response to 5-FU. Our results show that malignant cells of involved nodes were in a post mitotic phase of the cell cycle, and show a low proliferation index and TS expression, while the primary tumours and controls, were strongly positive. On these basis we can hypothesize that these cells could be less sensitive to 5-FU. Further studies are necessary to identify other mechanisms responsible for their metastasing capability and/or for their aggressiveness.

Relationship between thymidylate synthase and p53 and response to FEC versus taxane adjuvant chemotherapy for breast carcinoma.

Abstract Many drugs can be used for adjuvant therapy of breast cancer, including anthracyclines, cyclophosphamide, 5-fluorouracil (5-FU) and, recently, taxanes (TXT)have shown promising results. 5-FU blocks thymidylate synthase (TS) which cross-links p53 mRNA, inhibiting its synthesis. TS overexpression is one of the main mechanisms involved in 5-FU drug resistance. Enough p53 mutations can confer resistance to chemotherapy using anthracyclines and 5-FU, while are associated with improved responses to TXT. The aim of this study was to examine the TS and p53 levels in tumor samples and to compare the efficacy of FEC (5-FU, epirubicin, cyclophosphamide) and TXT chemotherapy in a group of patients with differing TS and p53 status. We examined 84 breast tumor samples using immunohistochemistry. TS and p53 levels were inversely related, and TS and p53 positivity was significantly associated with the failure of FEC treatment and with a good response to TXT therapy (p <0.001). This confirms the predictive role of these two markers, which should be considered when choosing the appropriate adjuvant therapy for breast cancer.

Thymidylate synthase polymorphism and microsatellite instability : association in colorectal cancer

5‐Fluorouracil (5FU) is the main drug used for the treatment of colorectal cancer (CRC) and Thymidilate Synthase (TS) is its target enzyme. TS gene has regulatory tandemly repeated sequences in its 5′ and 3′untraslated region (5′–3′ UTR). CRC often shows a kind of genomic instability called Microsatellite Instability (MSI) that is associated with TS levels and survival. Our data show that the genotype 2R/2R (homozygosity for 2 tandem repeat sequences in the 5′UTR) is more frequently associated with MSI + and lower TS levels. More over we did not find any significant association between the 2R/3R (heterozygosity for 2 and 3 tandem repeat sequences in the 5′UTR) and 3R/3R (homozygosity for 3 tandem repeat sequences in the 5′ UTR) genotypes with the MSI + and MSI −, while these genotypes were associated with a higher TS expression. As a consequence we can hypothesise that patients bearing CRC with the MSI +, the 2R/2R genotype and with low TS levels could have a better prognosis and they could not be drug resistant.