Login to Access Video or Poster Abstract: MP98-07
Sources of Funding: McIntyre

Introduction

The mechanisms of bladder cancer metastasis are incompletely understood. To this end, we performed gene expression profiling comparing matched primary tumors to lymph node metastases. LimD2, a gene previously implicated in papillary thyroid cancer metastasis through modulation of integrin signaling, was found to be upregulated in bladder cancer lymph node (LN) metastases. We sought to further characterize the relationship of LimD2 and bladder cancer metastasis.

Methods

RNA from both primary tumor and lymph node metastases from 29 patients with pN+ disease at cystectomy was collected and used for gene expression profiling. Immunohistochemistry was performed to confirm the results at the cellular and protein level. LimD2 expression in primary tumors was evaluated in silico in several cohorts including the TCGA. LimD2 expression in urothelial cancer cell lines of both basal and luminal molecular phenotypes was evaluated by western blot. Constructs resulting in LimD2 overexpression and knockdown were stably transfected in urothelial cancer cell lines which will then be used for in vitro and in vivo metastatic assays.

Results

In patient-matched cystectomy/lymphadenectomy samples, LimD2 RNA expression was 4.7 fold higher in lymph node metastases compared to primary tumors (paired t-test p< 0.0001). These results were confirmed at the cellular and protein level by immunohistochemistry in a subset of the same patient samples. In silico analysis in several cohorts showed that LimD2 expression in the primary tumor was higher in basal and TCGA cluster IV molecular phenotypes, compared with luminal phenotypes (p=0.039, p=0.002 respectively). This pattern was confirmed in urothelial cancer cell lines, as cells with a basal phenotype (T24, J82, TCCSUP) showed much higher expression of LimD2 protein compared with luminal phenotype cells (UC14, RT112, UC6).

Conclusions

LimD2 expression is upregulated during bladder cancer metastasis and is correlated with aggressive basal molecular phenotypes. Given its ability to modulate integrin signaling, LimD2 is mechanistically heavily implicated in bladder cancer metastasis.

Funding

McIntyre