The matrix-specific protein periostin (POSTN) is up-regulated in human cancers and associated with cancer growth, metastasis and angiogenesis. Although the stroma of cancer tissues is the main source of POSTN, it is still unclear how POSTN plays a role to facilitate the interplay between cancer cells and cancer-associated fibroblasts (CAFs) in head and neck cancer (HNC), thereby promoting tumorigenesis via modifying the tumor microenvironment. Herein, we have performed studies to investigate POSTN and its role in HNC microenvironment. Our results indicated that POSTN was significantly up-regulated in HNCs, especially in the tissues with lymph node metastasis. Moreover, POSTN was highly enriched in the stroma of cancer tissues and produced mainly by CAFs. More importantly, we have pinpointed TGF-β3 as the major upstream molecular that triggers the induction of POSTN in CAFs. As such, during the interaction between fibroblasts and cancer cells, the increased stromal POSTN induced by TGF-β3 directly accelerated the growth, migration and invasion of cancer cells. Hence, our study has provided a novel modulative role for POSTN on HNC progression and further reveals POSTN as an effective biomarker to predict metastasis as well as a potential cancer therapeutic target.

Cancer-associated fibroblasts (CAFs), a major component of cancer stroma, play an important role in cancer progression but little is known about how CAFs affect tumorigenesis and development. MicroRNAs (miRNAs) are small non-coding RNAs that can negatively regulate target mRNA expression at post-transcriptional levels. In head and neck cancer (HNC), our analysis of miRNA arrays showed that miR-7, miR-196 and miR-335 were significantly up-regulated in CAFs when compared with their paired normal fibroblasts (NFs). FAP, α-SMA and FSP, specific markers of CAFs, were significantly expressed in CAFs. Functionally, exogenous expression of miR-7 in NFs induced a functional conversion of NFs into CAFs. In contrast, inhibition of miR-7 expression in CAFs could induce a functional conversion of CAFs into NFs. Our study demonstrated that overexpression of miR-7 in NFs significantly increased the migration activity and growth rates of cancer cells in co-culture experiments. Mechanistically, we confirmed that the RASSF2-PAR-4 axis was mainly responsible for miR-7 functions in CAFs using bioinformatics methods. Overexpression of miR-7 in CAFs led to down-regulation of RASSF2, which dramatically decreased the secretion of PAR-4 from CAFs and then enhanced the proliferation and migration of the co-cultured cancer cells. Thus, these results reveal that the inactivation of the RASSF2-PAR-4 axis controlled by miR-7 may be a novel strategy for gene therapy in HNCs.

BackgroundIn our previous study, parathyroid hormone-like hormone (PTHLH) which encodes parathyroid hormone-related protein (PTHrP) was revealed to be up-regulated in oral squamous cell carcinoma (OSCC) compared with paired apparently normal surgical margins using microarray method. However, the function and prognostic indicators of PTHLH/PTHrP in OSCC remain obscure.MethodsThe mRNA levels of PTHLH and its protein levels were investigated in 9 OSCC cell lines and in 36 paired OSCC specimens by real-time PCR and western blotting. The biological function of PTHLH/PTHrP was investigated using small interfering RNA (siRNA) in 3 OSCC cell lines, and immunohistochemistry was used to estimate the prognostic value of PTHrP in 101 patients with head and neck squamous cell carcinoma (HNSCC), including OSCC and oropharyngeal squamous cell carcinoma. Cell cycle was tested by flow cytometry and cell cycle related genes were investigated by western blotting and immunocytochemistry assay.ResultsThis study showed that the mRNA and protein levels of PTHLH in 9 OSCC cell lines were much higher than that in normal epithelial cells (P < 0.0001). In 36 paired OSCC tissues, PTHLH mRNA expressions were found higher in 32 OSCC tissues than that of paired apparently normal surgical margins (P = 0.0001). The results revealed that the down-regulation of PTHLH/PTHrP by siRNAs could reduce cell proliferation and inhibit plate and soft agar colony formation as well as affect the cell cycle of OSCC cells. The key proteins related to the cell cycle were changed by anti-PTHLH siRNA. The results showed that cyclin D1 and CDK4 expressions were significantly reduced in the cells transfected with anti-PTHLH siRNA. On the other hand, the expression of p21 was increased. The results also showed that high PTHrP level was associated with poor pathologic differentiation (P = 0.0001) and poor prognosis (P = 0.0003) in patients with HNSCC.ConclusionsThis study suggests that PTHLH/PTHrP is up-regulated in OSCCs. Therefore, PTHLH/PTHrP could play a role in the pathogenesis of OSCC by affecting cell proliferation and cell cycle, and the protein levels of PTHrP might serve as a prognostic indicator for evaluating patients with HNSCCs.