Breast Cancer Research and Treatment 83: 109–117, 2004. © 2004 Kluwer Academic Publishers. Printed in the Netherlands. Report Calcitonin receptor gene and breast cancer: quantitative analysis with laser capture microdissection Xiaojuan Wang 1 , Misa Nakamura 1 , Ichiro Mori 1 , Koichi Takeda 1 , Yasushi Nakamura 1 , Hirotoshi Utsunomiya 1 , Goro Yoshimura 2 , Takeo Sakurai 2 , and Kennichi Kakudo 1 1 Department of Pathology, 2 Affiliated Kihoku Hospital, Wakayama Medical University, Wakayama City, Wakayama, Japan Key words: breast cancer, calcitonin receptor, laser capture microdissection, metastasis, real-time RT-PCR Summary There is a growing body of evidence indicating that calcitonin (CT) and its receptor (CTR) is involved in cell growth, differentiation and tissue development. Using laser capture microdissection (LCM) and real-time reverse transcription polymerase chain reactions (RT-PCR), we have investigated CTR mRNA expression in 60 primary breast cancers, including 14 pairs of matched cancers and unaffected ductal epithelia from the same patients. Our results demonstrate that CTR mRNA was constantly expressed in normal ductal epithelium and in breast cancer. In the 14 cases where matched samples were available, a decrease in CTR mRNA expression was found in 9 breast cancers (64.3%), an increased CTR expression in 2 cases (14.3%) and no significant change in 3 cases (21.4%). In 60 cases of primary breast cancers, decreased CTR expression was found in 44 (73.3%), increased CTR expression was detected in 10 cases (16.7%) and no change was observed in 6 cases (10%). Decreased CTR expression was found more often in cases with lymph node metastasis (p = 0.0498) and lymphatic invasion (p = 0.0179). Also there was a decreased CTR expression in cases with an extensive intraductal component (p = 0.0543) and a high nuclear grade (p = 0.1934), although this was not statistically significant. Overall, we conclude that CTR mRNA was constantly expressed in unaffected ductal epithelium, whereas decreased CTR mRNA expression was frequently found in breast cancers, particularly in cases with lymph node metastasis and lymphatic invasion. These results suggest that CTR might be of great potential significance in breast cancer progression. Introduction Calcitonin (CT) is a 32 amino acid peptide hormone secreted by C cells of the thyroid gland. The main physiological roles of CT are to regulate calcium metabolism to inhibit bone resorption via osteoclast and to increase Ca 2+ excretion via the kidney [1]. However, both CT and its receptor (CTR) have been identified in a large number of unrelated tissues and cells [2–4], suggesting that CT/CTR may have alter- native additional functions. There is a growing body of evidence that CT is involved in cell growth, differ- entiation, and tissue development [5, 6]. It has been shown that, cell proliferation was inhibited when hu- man breast cancer cells in culture were treated with CT [7–9]. Taken together with reports of the mito- genic action of CT in certain prostate cancer cell lines [10, 11], this suggests that CT may have a role in the modulation of cell proliferation. A transient ex- pression of CT in the pre-implantation phase uterus is critical for blastocyst differentiation and implantation via receptor-mediated Ca 2+ signaling [5, 6]. There is also evidence that CT is involved in cell survival and is able to induce apoptosis [12–14]. Jagger et al. [3, 15] reported that embryonic expression of mouse CTR and of a lacZ construct were driven by the CTR promoter, suggesting that CTR may play an important role in morphogenesis of mammary tissue. Autoradiographic and radioligand-binding tech- niques with iodinated CT have identified high-affinity CTRs in the human breast cancer cell lines, T47D and MCF-7 [7–9, 16], and in other human tissues