Abstract 3711: Regulation of oncogenic targets by miR-99a-3p (the passenger strand of the miR-99a-duplex) in head and neck squamous cell carcinoma
Authors: Okada Reona , Koshizuka Keiichi , Yamada Yasutaka , Moriya Shogo , Kikkawa Naoko , Kinoshita Takashi , Hanazawa Toyoyuki , Seki Naohiko 
Published: September 2020

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer, with approximately 650,000 new cases diagnosed annually and 400,000 HNSCC-related deaths worldwide each year. HNSCC is typically diagnosed when already at an advanced stage. Despite advancements in surgery, radiation therapy, and chemotherapy, patients with advanced HNSCC have a poor prognosis. The median overall survival time for patients with recurrence and metastasis is 10-13 months in the setting of first-line chemotherapy and 6 months in the second-line setting.

Many studies have shown that noncoding RNAs encoded by the human genome are functional and play critical roles in various cellular processes, e.g., cell growth, migration, invasion, and apoptosis. Among noncoding RNAs, microRNAs (miRNAs) are endogenous single-stranded RNA molecules comprising 19-22 nucleotides that function as fine-tuners of RNA expression. A single miRNA regulates many RNA transcripts, and bioinformatics studies have shown that more than half of protein-coding genes are controlled by miRNAs. Aberrantly expressed miRNAs are closely associated with cancer pathogenesis via the disruption of RNA networks within cancer cells.

To identify novel oncogenic targets in head and neck squamous cell carcinoma (HNSCC), we have analyzed antitumor microRNAs (miRNAs) and their controlled molecular networks in HNSCC cells. Based on our miRNA signature in HNSCC, both strands of the miR-99a-duplex (miR-99a-5p: the guide strand, and miR-99a-3p: the passenger strand) are downregulated in cancer tissues. Moreover, low expression of miR-99a-5p and miR-99a-3p significantly predicts poor prognosis in HNSCC, and these miRNAs regulate cancer cell migration and invasion. We previously showed that passenger strands of miRNAs have antitumor functions.

Here, we screened miR-99a-3p-controlled oncogenes involved in HNSCC pathogenesis. Thirty-two genes were identified as miR-99a-3p-regulated genes, and 10 genes (STAMBP, TIMP4, TMEM14C, CANX, SUV420H1, HSP90B1, PDIA3, MTHFD2, BCAT1, and SLC22A15) significantly predicted 5-year overall survival. Notably, among these genes, STAMBP, TIMP4, TMEM14C, CANX, and SUV420H1 were independent prognostic markers of HNSCC by multivariate analyses. We further investigated the oncogenic function of STAMBP in HNSCC cells using knockdown assays. Our data demonstrated that the aggressiveness of phenotypes in HNSCC cells was attenuated by siSTAMBP transfection. Moreover, aberrant STAMBP expression was detected in HNSCC clinical specimens by immunochemistry.

Our strategy, i.e., identification of antitumor miRNAs and their targets, maybe an attractive tool to reveal novel prognostic and therapeutic targets in HNSCC.

Citation Format: Reona Okada, Keiichi Koshizuka, Yasutaka Yamada, Shogo Moriya, Naoko Kikkawa, Takashi Kinoshita, Toyoyuki Hanazawa, Naohiko Seki. Regulation of oncogenic targets by miR-99a-3p (the passenger strand of the miR-99a-duplex) in head and neck squamous cell carcinoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3711.