MUC16 Regulates TSPYL5 for Lung Cancer Cell Growth and Chemoresistance by Suppressing p53

Abstract

Purpose MUC16, a tumor biomarker and cell surface associated mucin, is overexpressed in various cancers; however, its role in lung cancer pathogenesis is unknown. Here, we have explored the mechanistic role of MUC16 in lung cancer. Experimental Design To identify the functional role of MUC16, stable knockdown was carried in lung cancer cells with two different shRNAs. Clinical significance of MUC16 was evaluated in lung cancer patient’s tissues using IHC. We have generated genetically engineered mouse model (KrasG12D; AdCre) to evaluate the preclinical significance of MUC16. Results MUC16 was overexpressed (P=0.03) in lung cancer as compared to normal. MUC16 knockdown (KD) in various lung cancer cell lines decreased the in vitro growth rate (P<0.05), migration (P<0.001), and in vivo tumor growth (P=0.007), while overexpression of MUC16-carboxyl terminal (MUC16-Cter) resulted in increased growth rate (P<0.001). Transcriptome analysis of MUC16 KD showed a downregulation (P=0.005) of TSPYL5 gene, which encodes for a testis-specific Y-like protein. Rescue studies via over-expression of MUC16-Cter in MUC16 KD cells showed activation of signaling proteins such as JAK2 (Y1007/1008), STAT3 (Y705) and glucocorticoid receptor (GR), which constitutes an important axis for the regulation of TSPYL5 for oncogenic process. Further, inhibition of STAT3 (Y705) led to decreased GR and TSPYL5 suggesting that MUC16 regulates TSPYL5 through the JAK2/STAT3/GR axis. Also, MUC16 overexpression induced cisplatin and gemcitabine resistance by down regulation of p53. Conclusions Our findings indicate a significant role of MUC16 in tumorigenesis and metastasis of lung cancer cells possibly via regulation of TSPYL5 through JAK2/STAT3/GR axis.

Targeting MUC16 in Cancer Therapy

“…As a large glycoprotein, it is able to form a chemical barrier to protect the epithelium against hostile environmental conditions and pathogens [1,9]. However, cancer cells have an aberrant expression of mucins, which confers a number of oncogenic properties such as increased cell proliferation, evasion of the immune system and metastasis [1,3,10]. …”

“…MUC16 also binds to mesothelin, a protein involved in peritoneal metastases of ovarian cancers. Other properties include inhibition of apoptosis, contributing to chemotherapy resistance [8,11,18] and activation of STAT3 through JAK2, which increases cell proliferation [3,13]. Additionally, MUC16 is implicated in reducing the immune system response by binding to inhibitory receptors on natural killer (NK) cells [1,19] and decreasing expression of CD16, a cytokine that stimulates NK cells [20,21].…”

“…Furthermore, it is also involved in mediating resistance to platinum based genotoxic drugs through increased expression of TSPYL5 (testis-specific Y-like protein). TSPL5 can subsequently bind to ubiquitin specific protease to inactivate p53, a tumour suppressor protein [3].…”

“…It is a well-established biomarker used to monitor the progression and recurrence of ovarian cancer. Furthermore, it is overexpressed in a range of human malignancies including ovarian, pancreatic, breast, cholangiocarcinoma, cervical, gastric and non-small cell lung cancer [1][2][3][4][5][6]. Mucins are a family of high molecular weight glycoproteins composed of oligosaccharides attached to a peptide core [7].…”

“…Several hundred oligosaccharides are attached to the N-terminal domain through O-linked glycosylation and N-linked glycosylation whilst the tandem repeat region (TRR) has approximately 60 repeats of a 156 amino acid sequence, with disulphide bonds that confers structural stability. Attached to the TRR is a smaller C-terminal domain that also contains a cytoplasmic tail involved in intracellular cell events ( Figure 1) [1,3,8].…”