Panoply™ Human TACSTD2 Knockdown Stable Cell Line

The DNA methyltransferase 1 inhibitor 5-aza-2′-deoxycytidine (5-Aza-dC) is a potential treatment for breast cancer. However, not all breast tumors respond similarly to 5-Aza-dC treatment, and little is known about the response of hormone-resistant breast cancer to 5-Aza-dC. One of the identified genes, tumor-associated calcium signaling transducer 2 (TACSTD2), is altered by DNA methylation, and there is evidence that reduced expression may lead to increased proliferation in some cancers. Analysis of DNA methylation of TACSTD2 and protein expression of its product, trophoblast antigen protein 2 (TROP2), was extended to primary (n = 34) and recurrent (n = 34) breast tumor cohorts. Stratification of tumors by recurrence and ER status revealed no significant relationship between TROP2 levels and TACSTD2 methylation. However, knockdown of TACSTD2 expression in MCF7 increased proliferation; re-expression of TACSTD2 in TMX2-28 did not inhibit proliferation, indicating that TACSTD2 re-expression alone is not sufficient to explain the decreased proliferation observed after treatment with 5-Aza-dC.

To investigate the role of TROP2 in regulating proliferation, researchers generated stable TACSTD2 knockdown cell lines (MCF7-TACSTD2-Kd) and TACSTD2 overexpression cell lines (TMX2-28-TACSTD2). Additionally, control cell lines were generated using vectors containing either a scrambled control shRNA (MCF7-Control) or lacking the TACSTD2 coding sequence (TMX2-28-Control) (Figure 1a). Immunohistochemistry (IHC) of stained cultures revealed decreased TROP2 expression in the TACSTD2 knockdown cell lines and increased expression in the TACSTD2 overexpression cell lines (Figure 1c and d). If TROP2 plays a major role in the phenotypes observed after 5-Aza-dC treatment, TMX2-28-TACSTD2 cells should exhibit decreased proliferation compared to TMX2-28-Control cells. Contrary to expectations, proliferation was not decreased in TMX2-28-TACSTD2 cells. Also surprisingly, knockdown of TACSTD2 in MCF7 resulted in a slight increase in proliferation (25%) compared with MCF7-Control (Figure 1b).

Figure 1. TACSTD2 expression and proliferation and stable expression of TROP2 in TMX2-28 and knockdown of TROP2 in MCF7. (Zimmers S M, et al., 2018)