Analysis of oncogenic activities of protein kinase D1 in head and neck squamous cell carcinoma

Abstract

BackgroundHead and neck squamous cell carcinoma (HNSCC) is the sixth leading cause of cancer death in the US. The protein kinase D (PKD) family has emerged as a promising target for cancer therapy with PKD1 being most intensively studied; however, its role in HNSCC has not been investigated.MethodsThe expression of PKD was evaluated in human HNSCC by quantitative RT-PCR, Western blot and immunohistochemistry. Cell proliferation, wound healing, and matrigel invasion assays were performed upon siRNA-mediated knockdown of PKD1 in HNSCC cells, and subcutaneous xenograft mouse model was established by implantation of the stable doxycycline (Dox)-inducible PKD1 expression cell lines for analysis of tumorigenic activity in vivo.ResultsPKD1 was frequently downregulated in HNSCC cell lines at both transcript and protein levels. In human HNSCC tissues, PKD1 was significantly down-regulated in localized tumors and metastases, and in patient-paired tumor tissues as compared to their normal counterparts, which was in part due to epigenetic modification of the PRKD1 gene. The function of PKD1 in HNSCC was analyzed using stable doxycycline-inducible cell lines that express native or constitutive-active PKD1. Upon induction, the rate of proliferation, survival, migration and invasion of HNSCC cells did not differ significantly between the control and PKD1 overexpressing cells in the basal state, and depletion of endogenous PKD1 did not impact the proliferation of HNSCC cells. However, the median growth rate of the subcutaneous HNSCC tumor xenografts over time was elevated with PKD1 induction, and the final tumor weight was significantly increased in Dox-induced vs. the non-induced tumors. Moreover, induced expression of PKD1 promoted bombesin-induced cell proliferation of HNSCC and resulted in sustained ERK1/2 activation in response to gastrin-releasing peptide or bombesin stimulation, suggesting that PKD1 potentiates GRP/bombesin-induced mitogenic response through the activation of ERK1/2 in HSNCC cells.ConclusionsOur study has identified PKD1 as a frequently downregulated gene in HNSCC, and functionally, under certain cellular context, may play a role in GRP/bombesin-induced oncogenesis in HNSCC.Electronic supplementary materialThe online version of this article (10.1186/s12885-018-4965-6) contains supplementary material, which is available to authorized users.

State-Transition Analysis of Time-Sequential Gene Expression Identifies Critical Points That Predict Development of Acute Myeloid Leukemia

“…Prkd1 encodes a serine/threonine protein kinase and is part of all top three ranked GO terms enriched for persistent events. The specific role of PRKD1 in AML has not been described; however, it is known to promote invasion, cancer stemness, and drug resistance in several solid tumors (30)(31)(32). In addition to these genes, our approach identified many other genes showing a strong contribution to leukemia development (Supplemenatry Table S8-S11).…”

Deciphering the Role of Protein Kinase D1 (PKD1) in Cellular Proliferation

“…Consistently, the development of robust techniques allowing the direct and precise measurement of PKD1 activity would be a major breakthrough in the field of PKD1 studies. Moreover, a very recent study showed that a direct correlation cannot be automatically made between the relative PKD1 expression levels in normal and tumor tissues and its role in tumorigenesis (109). In fact, PKD1 is significantly downregulated in head and neck localized tumors and metastases compared with normal tissues due to epigenetic modifications, suggesting an antiproliferative role of this protein.…”

“…In fact, PKD1 is significantly downregulated in head and neck localized tumors and metastases compared with normal tissues due to epigenetic modifications, suggesting an antiproliferative role of this protein. However, its expression has been positively correlated with both the subcutaneous head and neck squamous cell carcinoma xenografts growth and a sustained bombesin-induced ERK1/2 activation demonstrating a proproliferative role of this protein (109). In addition, despite numerous studies concerning PKD1, most of the data come from experimental studies and very few information come from cohort ones.…”

State-Transition Analysis of Time-Sequential Gene Expression Identifies Critical Points That Predict Leukemia Development

“…Prkd1 encodes a serine/threonine protein kinase and is part of all top 3 ranked GO terms enriched for persistent events. The specific role of PRKD1 in AML has not been described, however, it is known to promote invasion, cancer stemness and drug resistence in several solid tumors (Döppler et al, 2016;Kim et al, 2016;Zhang et al, 2018). These results highlight the relevance of Page 22 of 40 biological insights provided by the geometry of the transcriptome state-space and critical points of state-transition theory.…”