The in vitro influences of epidermal growth factor and heregulin-β1 on the efficacy of trastuzumab used in Her-2 positive breast adenocarcinoma

Abstract

BackgroundHuman epidermal growth factor receptor-2 (Her-2) is over expressed in approximately 25-30% of all primary breast tumors resulting in a distinctive breast cancer subtype associated with a poor prognosis and a decrease in overall survival. Trastuzumab (Herceptin®), an anti-Her-2 monoclonal antibody, has dramatically altered the prognosis of Her-2 positive breast cancer. Trastuzumab is, however, associated with primary and acquired resistance.Aim and methodsTo investigate the in-vitro effects of trastuzumab on cell viability (tetrazolium conversion assay), cell cycling (propidium iodide staining), apoptosis (executioner caspases and annexin-V) and relative surface Her-2 receptor expression (anti-Her-2 affibody molecule) in Her-2-positive (SK-Br-3) and oestrogen receptor positive (MCF-7) breast adenocarcinoma cells and to determine potential augmentation of these effects by two endogenous ligands, epidermal growth factor (EGF) and heregulin-β1 (HRG- β1).ResultsCell viability was decreased in SK-Br-3 cells by exposure to trastuzumab. This was associated with G1 accumulation and decreased relative surface Her-2 receptor density, supporting the cytostatic nature of trastuzumab in vitro. SK-Br-3 cells exposed to EGF and heregulin-β1 produced differential cell responses alone and in combination with trastuzumab, in some instances augmenting cell viability and cell cycling. Relative surface Her-2 receptor density was reduced substantially by trastuzumab, EGF and heregulin-β1. These reductions were amplified when ligands were used in combination with trastuzumab.ConclusionCell type specific interactions of endogenous ligands appear to be dependent on absolute Her-receptor expression and cross activation of signaling pathways. This supports the notion that receptor density of Her-family members and multiplicity of growth ligands are of mutual importance in breast cancer cell proliferation and therefore also in resistance associated with trastuzumab.

Targeted therapies in breast cancer: New challenges to fight against resistance

“…The efficacy of trastuzumab in inhibiting proliferation of breast cancer cells might be dependent on the presence of endogenous HER-receptor activating ligands EGF and heregulin-β1; the receptor density of HER-family members and growth ligands are key players in the development of resistance mechanisms to trastuzumab therapy, which interfers with cell cycle kinetics by inducing a G1 accumulation in HER-2 positive breast adenocarcinomas[78]. …”

Gemcitabine‐(5′‐phosphoramidate)‐[anti‐IGF‐1R]: molecular design, synthetic organic chemistry reactions, and antineoplastic cytotoxic potency in populations of pulmonary adenocarcinoma (A549)

“…Similar to monoclonal anti‐HER2/ neu (Herceptin) and anti‐EGFR (cetuximab) immunoglobulin fractions on neoplastic adenocarcinoma and carcinoma cell types, both anti‐CD20 (rituximab, ofatumumab) and anti‐CD52 (alemtuzumab) disrupt growth and vitality of leukemia and lymphoma cell types. Both anti‐CD20 (rituximab, ofatumumab) and anti‐CD52 (alemtuzumab) are effective against B‐cell chronic lymphocytic leukemia (B‐CLL) cell populations. Simultaneous anti‐CD20 (rituximab) in combination with cyclophosphamide–doxorubicin–vincristine–prednisone (CHOP) increases survival over CHOP alone in conditions of high‐grade lymphomas .…”

“…Monoclonal IgG binding at these sites can serve as a molecular strategy for suppressing the biological integrity and function of neoplastic cell populations. [29] Most notable in this regard is neoplastic cell viability, [30,31] proliferation rate, [31,32] local invasiveness, [33] metastatic potential, [34,35] and chemotherapeutic resistance (e.g., P-glycoprotein co-expression). [33,36,37] Endogenous trophic receptors or cell-differentiating antigens that are uniquely or highly overexpressed on the exterior surface membrane of neoplastic populations can also be utilized to facilitate the selective 'targeted' delivery of chemotherapeutic moieties.…”

“…Monoclonal IgG binding at these sites can serve as a molecular strategy for suppressing the biological integrity and function of neoplastic cell populations . Most notable in this regard is neoplastic cell viability, proliferation rate, local invasiveness, metastatic potential, and chemotherapeutic resistance (e.g., P‐glycoprotein co‐expression) …”

Fludarabine- (C2-methylhydroxyphosphoramide)- [anti-IGF-1R]: Synthesis and Selectively Targeted Anti-Neoplastic Cytotoxicity against Pulmonary Adenocarcinoma (A549)

“…Significant advances have been made in identifying trophic membrane receptors over-expression in many adenocarcinoma and carcinoma affecting the breast, prostate, intestine, ovary or kidney and the implications of this phenomenon on cancer cell biological phenomenon [36] as it pertains to viability [37,38] proliferation rate [38,39], local invasiveness [40] metastatic potential [41,42] and chemotherapeutic resistance (e.g. P-glycoprotein co-expression) [40,43,44].…”