Association of augmented immune-staining of G-quadruplex tertiary DNA structure in chemo-tolerant TNBC with downregulation of WNT/epidermal growth factor receptor pathway receptor genes a pilot clinicopathological study

The aim of the study is to understand the involvement of G-Quadruplex (G-Q) structures in altering the expression profile of WNT/epidermal growth factor receptor (EGFR) pathway receptor genes in chemo-tolerant Triple Negative Breast Cancer (TNBC) samples. At first, Gene Expression Omnibus datasets were mined where the expression profile of WNT/EGFR pathway genes in TNBC samples and MDA-MB-231, a TNBC cell line, were checked in response to doxorubicin, a chemotherapeutic drug. Next, to unveil the probable mechanism of regulation, the presence of G-Q structure was checked in in silico study and later validated by immunohistochemical analyses in our pool of sample. These observed results were correlated with patient's demography and survival status. Expression of the receptors (FZD7, LRP6, EGFR) of the WNT/EGFR pathway were found to be differentially expressed in TNBC samples; further emphasized in our samples (n = 61). Notably, these G-Q structures were found in the promoter region of the WNT pathway receptor genes (FZD7, LRP6, and EGFR). Validating in our patient sample pool, a significant increase in G-Q immunostaining was observed in samples, after neoadjuvant chemotherapy (NACT) samples (n = 17) than the pretherapeutic samples (n = 44). Similar pattern of G-Q immunostaining was noticed in doxorubicin-treated MDA-MB-231 cell line. Intriguingly, low staining of G-Q among the pretherapeutic samples, but NACT TNBC samples, was found to be significantly correlated with lymph node metastasis. This study showed that the augmented immunostaining of G-Q structure might have an important involvement in regulating the expression pattern of the WNT/EGFR pathway genes in response to doxorubicin treatment of TNBC