KLF4 defines the efficacy of the epidermal growth factor receptor inhibitor, erlotinib, in triple-negative breast cancer cells by repressing the EGFR gene

Abstract

Background: Triple-negative breast cancer (TNBC) is characterized by high rates of recurrence and poor overall survival. This is due, in part, to a deficiency of targeted therapies, making it essential to identify therapeutically targetable driver pathways of this disease. While epidermal growth factor receptor (EGFR) is expressed in 60% of TNBCs and drives disease progression, attempts to inhibit EGFR in unselected TNBC patients have had a marginal impact on outcomes. Hence, we sought to identify the mechanisms that dictate EGFR expression and inhibitor response to provide a path for improving the utility of these drugs. In this regard, the majority of TNBCs express low levels of the transcription factor, Krüppel-like factor 4 (KLF4), while a small subset is associated with high expression. KLF4 and EGFR have also been reported to have opposing actions in TNBC. Thus, we tested whether KLF4 controls the expression of EGFR and cellular response to its pharmacological inhibition. Methods: KLF4 was transiently overexpressed in MDA-MB-231 and MDA-MB-468 cells or silenced in MCF10A cells. Migration and invasion were assessed using modified Boyden chamber assays, and proliferation was measured by EdU incorporation. Candidate downstream targets of KLF4, including EGFR, were identified using reverse phase protein arrays of MDA-MB-231 cells following enforced KLF4 expression. The ability of KLF4 to suppress EGFR gene and protein expression and downstream signaling was assessed by RT-PCR and western blot, respectively. ChIP-PCR confirmed KLF4 binding to the EGFR promoter. Response to erlotinib in the context of KLF4 overexpression or silencing was assessed using cell number and dose-response curves.

KLF4 transcription factor in tumorigenesis

“…The discrepancy maybe related to alterations in major signaling pathways caused by different cancer types/subtypes. KLF4 inhibited the breast cancer cells growth, metastasis, and invasion through inhibition of Snail, estrogen receptor, and epidermal growth factor receptor [ 67 – 69 ]. In contrast, knockdown of SIRT1 downregulated KLF4 and inhibited the stemness of breast cancer cells [ 70 ].…”

Exosomal targeting and its potential clinical application

“…Nucleic acid drugs have therapeutic potential to a certain extent, but their clinical application is limited by the lack of appropriate drug delivery carriers. Epidermal growth factor receptor (EGFR) is associated with the progression of a variety of cancers, including breast cancer [103], lung cancer [104,105], cervical cancer [106], and colorectal cancer [107]. The increased expression of EGFR in some epithelial tumors can be used as a receptor target for cancer drug delivery system [108].…”

A recent development of new therapeutic agents and novel drug targets for cancer treatment

“… 61 Trastuzumab, the humanized anti-human epidermal growth factor receptor 2 (HER2) monoclonal antibody, which activates the immune system and targets HER2 to block the physiologic function of the HER2-signaling network has been revealed a noticeable therapeutic value in patients with HER2-positive metastases breast cancer. 9 , 62 HER2 is overexpressed about 20% of all breast cancer. Trastuzumab and pertuzumab and antibody–drug conjugates (trastuzumab emtansine and trastuzumab druxtecan) have a clinical outcome for HER2-positive breast cancer.…”