TLR4 has a TP53-dependent dual role in regulating breast cancer cell growth

Abstract

Breast cancer is a leading cause of cancer-related death, and it is important to understand pathways that drive the disease to devise effective therapeutic strategies. Our results show that Toll-like receptor 4 (TLR4) drives breast cancer cell growth differentially based on the presence of TP53, a tumor suppressor. TP53 is mutationally inactivated in most types of cancer and is mutated in 30-50% of diagnosed breast tumors. We demonstrate that TLR4 activation inhibits growth of TP53 wild-type cells, but promotes growth of TP53 mutant breast cancer cells by regulating proliferation. This differential effect is mediated by changes in tumor cell cytokine secretion. Whereas TLR4 activation in TP53 mutant breast cancer cells increases secretion of progrowth cytokines, TLR4 activation in TP53 wild-type breast cancer cells increases type I IFN (IFN-γ) secretion, which is both necessary and sufficient for mediating TLR4-induced growth inhibition. This study identifies a novel dichotomous role for TLR4 as a growth regulator and a modulator of tumor microenvironment in breast tumors. These results have translational relevance, demonstrating that TP53 mutant breast tumor growth can be suppressed by pharmacologic TLR4 inhibition, whereas TLR4 inhibitors may in fact promote growth of TP53 wild-type tumors. Furthermore, using data generated by The Cancer Genome Atlas consortium, we demonstrate that the effect of TP53 mutational status on TLR4 activity may extend to ovarian, colon, and lung cancers, among others, suggesting that the viability of TLR4 as a therapeutic target depends on TP53 status in many different tumor types.reast cancer has one of the highest incidence rates of cancer in women worldwide, with more than 1.5 million women diagnosed with the disease in 2012. Owing to its high incidence, breast cancer is also one of the leading causes of cancer-related deaths, with 40,000 women predicted to die of the disease in 2014 in the US alone. The diagnosis and treatment of breast cancer has been significantly improved by the identification of three major subtypes of the disease based on receptor expression: estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-positive, and triple-negative [tumors lacking ER, progesterone receptor (PR), and HER2]. Of these subtypes, ER-positive breast cancer accounts for 70-80% of all diagnosed breast tumors.ER-positive breast cancer is largely responsive to endocrine therapy; however, intrinsic or acquired resistance occurs in onethird of cases and contributes significantly to breast cancerassociated mortality. Therefore, identifying therapeutic targets to prevent ER-positive breast cancer mortality is a major focus of scientific investigation. ER-positive breast tumors with a high mutation load are associated with poor patient survival, and a high mutation load likely affects the response to endocrine therapy (1). Because known drivers of endocrine resistance (e.g., PR negativity and HER2 amplification) are not enriched in this subset, the identification of no...

Retracted: Effects of RNA interference‐mediated silencing of toll‐like receptor 4 gene on proliferation and apoptosis of human breast cancer MCF‐7 and MDA‐MB‐231 cells: An in vitro study

“…The experiment was repeated three times. NC, negative control; TLR4, toll-like receptor 4; RT-qPCR, reverse transcription quantitative polymerase chain reaction; CDK4, Cyclin-dependent kinase4 antibody; c-FLIP, FLICE-inhibitoryprotein cancer could be induced on disruption of TLR4 gene function in some breast tumors (Haricharan & Brown, 2015). A high expression of TLR4 has been observed in human breast cancer tissues, compared to its minimal expression in normal breast tissues (Yang et al, 2014).…”

Loss of MutL Disrupts CHK2-Dependent Cell-Cycle Control through CDK4/6 to Promote Intrinsic Endocrine Therapy Resistance in Primary Breast Cancer

“…Cell lines were obtained from American Type Culture Collection (ATCC, 2015) and maintained and validated as previously reported (44) Mycoplasma tests were performed on parent cell lines and stable cell lines every 6 months (latest test: 05/17) with the Lonza Mycoalert Plus kit (cat# LT07-710) as per manufacturer’s instructions. Cell lines were discarded at <25 passages, and fresh vials were thawed out.…”

“…Transfection and validation of CRISPR and shRNA plasmids was conducted as previously 23 . Transient transfection with siRNA against CHEK2 was conducted as previously(44), and siRNA pools were purchased from Sigma Aldrich. Stable cell lines were established in the presence of specified antibiotics at recommended concentrations.…”

“…Stable cell lines were established in the presence of specified antibiotics at recommended concentrations. Growth assays were conducted in triplicate and repeated independently as previously using Alamar blue to identify cell viability(44). Growth assay results were plotted as fold change in growth from Day1 to Day7, and normalized to vehicle control where specified.…”

Molecularly targeted therapies for p53-mutant cancers

“…Therefore, TLR4 appears to be a promising target for immune-based therapeutic options and is the focus of many drugs currently in development. However, a recent study demonstrated that TLR4 activation promotes cell growth in p53-mutant breast cancers, but inhibits cell growth in p53 wildtype breast cancers (129). The differential effects appear to be mediated by tumor cell cytokine secretions upon TLR4 activation.…”