Loss of Leucine Zipper Putative Tumor Suppressor 1 (LZTS1) Expression Contributes to Lymph Node Metastasis of Breast Invasive Micropapillary Carcinoma

Breast invasive micropapillary carcinoma (IMPC) is a rare subtype of breast cancer with a high potential of lymph node metastasis, aggressive clinical behavior, and poor disease-free or overall survival. Expression of leucine zipper putative tumor suppressor 1 (LZTS1) was frequently lost or reduced in breast cancer tissues. This study investigated the expression of LZTS1 protein in breast IMPC tissues using immunohistochemistry. In addition, somatic LZTS1 mutations and promoter methylation were assessed to determine an association with clinicopathological data from IMPC patients. LZTS1 protein was downregulated in 62 (62 %) of 100 IMPC tissue samples and was significantly associated with lymph node metastasis (P < 0.05). A LZTS1 exon mutation occurred in one of the 53 IMPC cases analyzed, whereas a LZTS1 intron mutation occurred in 26 of 53 cases. Moreover, LZTS1 promoter was frequently methylated in IMPC samples and was associated with reduced LZTS1 expression levels in IMPC tissues. These data demonstrated that the loss of LZTS1 expression was associated with lymph node metastasis in patients with IMPC, and LZTS1 promoter methylation could be responsible for the loss of LZTS1 expression.