Downregulation of Rab23 in Prostate Cancer Inhibits Tumor Growth In Vitro and In Vivo

MicroRNA-367-3p directly targets RAB23 and inhibits proliferation, migration and invasion of bladder cancer cells and increases cisplatin sensitivity

OBJECTIVES

This study investigated the biological role of miR-367-3p upregulation in bladder cancer and verified the mutual relation between miR-367-3p and RAB23.

MATERIALS AND METHODS

Expression levels of miR-367-3p were determined by RT-qPCR in bladder cancer cell lines and human bladder cancer tissues. The effects of miR-367-3p on proliferation, migration and invasion were evaluated by cell colony formation assays, wound healing assays and trans-well assays, respectively. The effects of miR-367-3p and RAB23 on cisplatin sensitivity of bladder cancer cells were assessed by CCK-8 assay. The expression of its target-RAB23 was determined by western blotting in T24, 5637. Plasmids used in dual-luciferase assays were constructed to confirm the action of miR-367-3p on downstream target-RAB23 in T24 cells. And also, the role of miR-367-3p in tumorigenesis was also confirmed in nude mouse models.

RESULTS

The downregulation of miR-367-3p was observed in human bladder cancer tissues. MiR-367-3p downregulation positively correlated with tumor stage and tumor grade. MiR-367-3p overexpression in T24, 5637 cells suppressed the proliferation, migration, and invasion of bladder cancer cells in vitro while decreasing IC50 values under T24 and 5637 cisplatin treatment conditions. RAB23 was shown to be upregulated in bladder cancer tissues and cell lines. MiR-367-3p directly bound to the 3' UTR of RAB23 in T24 cells. RAB23 was potentially accounted for the aforementioned functions of miR-367-3p. Tumor formation experiments in nude mouse models confirmed that overexpression of miR-367-3p could inhibit tumor growth and invasion in vivo.

CONCLUSIONS

miR-367-3p acts as a tumor suppressor in bladder cancer by downregulating RAB23 signaling. We conjecture that miR-367-3p-mediated downregulation of RAB23 expression may be a new therapeutic strategy for bladder cancer treatment.

Hedgehog signaling in tissue homeostasis, cancers, and targeted therapies

The past decade has seen significant advances in our understanding of Hedgehog (HH) signaling pathway in various biological events. HH signaling pathway exerts its biological effects through a complex signaling cascade involved with primary cilium. HH signaling pathway has important functions in embryonic development and tissue homeostasis. It plays a central role in the regulation of the proliferation and differentiation of adult stem cells. Importantly, it has become increasingly clear that HH signaling pathway is associated with increased cancer prevalence, malignant progression, poor prognosis and even increased mortality. Understanding the integrative nature of HH signaling pathway has opened up the potential for new therapeutic targets for cancer. A variety of drugs have been developed, including small molecule inhibitors, natural compounds, and long non-coding RNA (LncRNA), some of which are approved for clinical use. This review outlines recent discoveries of HH signaling in tissue homeostasis and cancer and discusses how these advances are paving the way for the development of new biologically based therapies for cancer. Furthermore, we address status quo and limitations of targeted therapies of HH signaling pathway. Insights from this review will help readers understand the function of HH signaling in homeostasis and cancer, as well as opportunities and challenges of therapeutic targets for cancer.

Bone Marrow Mesenchymal Stem Cells (BMSCs)-Derived miR-206 Promotes Breast Cancer Development by Activating Hedgehog Gene Signaling

Bone marrow-derived mesenchymal stem cells (BMSCs) are an integral part of the tumor microenvironment and involved in tumor evolution. Our aim is to further illuminate the relationship of exosomes of BMSC origin and breast cancer cells in breast cancer. Differential diagnosis was performed by identifying exosomal miR-206 secreted by BMSCs, and RT-PCR detected miR-206 expression in tumor tissues. Transwell assayed cell function and Target scan analyzed the regulatory relationship between Rab23 and miR-206. Rab23 expression was examined by western-blot after the addition of Rab23 and the effect of Rab23 on hedgehog was further verified. We demonstrated that exosomal miR-206 from BMSCs is expressed in tumor tissues and miR-206 mimics significantly inhibited tumor cell invasion and proliferation. miR-206 targets Rab23 and negatively regulates its expression. Further results showed that the addition of Rab23 could activate hedgehog signaling and promote the development of breast cancer. In conclusion, our study reveals that BMSC-derived miR-206 activates hedgehog gene signaling and promotes the breast carcinogenesis development by regulating Rab23 expression.

Advances in glioma-associated oncogene (GLI) inhibitors for cancer therapy

The Hedgehog/Glioma-associated oncogene homolog (HH/GLI) signaling pathway regulates self-renewal of rare and highly malignant cancer stem cells, which have been shown to account for the initiation and maintenance of tumor growth as well as for drug resistance, metastatic spread and relapse. As an important component of the Hh signaling pathway, glioma-associated oncogene (GLI) acts as a key signal transmission hub for various signaling pathways in many tumors. Here, we review direct and indirect inhibitors of GLI; summarize the abundant active structurally diverse natural GLI inhibitors; and discuss how to better develop and utilize GLI inhibitors to solve the problem of drug resistance in tumors of interest. In summary, GLI inhibitors will be promising candidates for various cancer treatments.

Molecular interactions of miR-338 during tumor progression and metastasis

Background

Cancer, as one of the main causes of human deaths, is currently a significant global health challenge. Since the majority of cancer-related deaths are associated with late diagnosis, it is necessary to develop minimally invasive early detection markers to manage and reduce mortality rates. MicroRNAs (miRNAs), as highly conserved non-coding RNAs, target the specific mRNAs which are involved in regulation of various fundamental cellular processes such as cell proliferation, death, and signaling pathways. MiRNAs can also be regulated by long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs). They are highly stable in body fluids and have tumor-specific expression profiles, which suggest their suitability as efficient non-invasive diagnostic and prognostic tumor markers. Aberrant expression of miR-338 has been widely reported in different cancers. It regulates cell proliferation, migration, angiogenesis, and apoptosis in tumor cells.

Main body

In the present review, we have summarized all miR-338 interactions with other non-coding RNAs (ncRNAs) and associated signaling pathways to clarify the role of miR-338 during tumor progression.

Conclusions

It was concluded that miR-338 mainly functions as a tumor suppressor in different cancers. There were also significant associations between miR-338 and other ncRNAs in tumor cells. Moreover, miR-338 has a pivotal role during tumor progression using the regulation of WNT, MAPK, and PI3K/AKT signaling pathways. This review highlights miR-338 as a pivotal ncRNA in biology of tumor cells.

Dietary Fructose Promotes Prostate Cancer Growth

Clinical localization of primary tumors and sites of metastasis by PET is based on the enhanced cellular uptake of 2-deoxy-2-[¹⁸F]-fluoro-D-glucose (FDG). In prostate cancer, however, PET-FDG imaging has shown limited clinical applicability, suggesting that prostate cancer cells may utilize hexoses other than glucose, such as fructose, as the preferred energy source. Our previous studies suggested that prostate cancer cells overexpress fructose transporters, but not glucose transporters, compared with benign cells. Here, we focused on validating the functional expression of fructose transporters and determining whether fructose can modulate the biology of prostate cancer cells in vitro and in vivo. Fructose transporters, Glut5 and Glut9, were significantly upregulated in clinical specimens of prostate cancer when compared with their benign counterparts. Fructose levels in the serum of patients with prostate cancer were significantly higher than healthy subjects. Functional expression of fructose transporters was confirmed in prostate cancer cell lines. A detailed kinetic characterization indicated that Glut5 represents the main functional contributor in mediating fructose transport in prostate cancer cells. Fructose stimulated proliferation and invasion of prostate cancer cells in vitro. In addition, dietary fructose increased the growth of prostate cancer cell line-derived xenograft tumors and promoted prostate cancer cell proliferation in patient-derived xenografts. Gene set enrichment analysis confirmed that fructose stimulation enriched for proliferation-related pathways in prostate cancer cells. These results demonstrate that fructose promotes prostate cancer cell growth and aggressiveness in vitro and in vivo and may represent an alternative energy source for prostate cancer cells. SIGNIFICANCE: This study identifies increased expression of fructose transporters in prostate cancer and demonstrates a role for fructose as a key metabolic substrate supporting prostate cancer cells, revealing potential therapeutic targets and biomarkers.

Long Non-Coding RNA MEG3 Modifies Cell-Cycle, Migration, Invasion, and Proliferation Through AKAP12 by Sponging miR-29c in Meningioma Cells

Meningioma (MEN) is a common central nervous system disease. Accumulating evidence indicated that long non-coding RNA maternally expressed gene 3 (MEG3) participated in the progression of MEN. However, the potential mechanisms of MEG3 in altering the aggressive phenotypes of MEN need further exploration. Levels of MEG3, microRNA (miR)-29c, and A-kinase anchor protein 12 (AKAP12) were determined using quantitative real-time Polymerase Chain Reaction (qRT-PCR) assay. Dual-luciferase reporter and RNA immunoprecipitation (RIP) assays were performed to verify the relationship between miR-29c and MEG3 or AKAP12. The protein level of AKAP12 was detected by western blot. Moreover, cell-cycle arrest, migration, invasion, and proliferation were assessed by flow cytometry, wound healing, transwell assays, and CCK-8 assay, respectively. Levels of MEG3 and AKAP12 were downregulated, while miR-29c was effectively increased in MEN tissues and cell line. Mechanically, MEG3 was a sponge of miR-29c to regulate the expression of AKAP12. Functionally, increase of MEG3 diminished cell-cycle, migration, invasion, and proliferation in MEN cells, and reintroduction of miR-29c could eliminate these effects. In addition, AKAP12 depletion overturned the inhibitory effects of miR-29c absence on cell-cycle, migration, invasion, and proliferation in vitro. Also, AKAP12 was co-regulated by MEG3/miR-29c axis. MEG3 mediated the aggressive behaviors of MEN cells via miR-29c/AKAP12 axis, supporting that MEG3 served as a promising biomarker for the diagnosis and treatment of human MEN.

CircHIPK3 Promotes Thyroid Cancer Tumorigenesis and Invasion through the Mirna-338-3p/RAB23 Axis

Objective：Thyroid cancer is a common type of endocrine malignancy, and its incidence has been steadily increasing in many regions of the world. Numerous studies have found that the circRNAs in various cancer types are aberrantly expressed, which could be potential biological diagnostic markers and therapeutic targets. The purpose of this study was to investigate the role of circHIPK3 in the development and progression of thyroid cancer and its mechanism. Subject and Methods：qRT-PCR was used to detect the relative expression levels of circHIPK3 in thyroid cancer cell lines (K1, CAL-62, TPC1), human thyroid normal cells (Nthy-ori 3-1), 10 pairs of thyroid cancer tissues and corresponding adjacent normal tissues. CCK-8 and Transwell assays were used to detect the proliferation and metastasis ability of cells. The targeted relationships between circHIPK3-miR-338-3p and miR-338-3p-RAB23 were predicted by bioinformatics analysis and verified by dual-luciferase reporter assays. Results and Conclusion: The downregulation of circHIPK3 significantly reduced the migration, invasion and proliferation of thyroid carcinoma. Then, we demonstrated that circHIPK3 up-regulated the expression of its target gene RAB23 by sponging miR-338-3p to promote the tumorigenesis and invasiveness of thyroid cancer. This study is the first to find that circHIPK3 plays the role of oncogenetic circRNA in thyroid cancer, which may provide new insights into how circRNA affects the progression of thyroid cancer. Our study also showed that circHIPK3 could be a novel biomarker for thyroid cancer.

LINC00689 promotes prostate cancer progression via regulating miR-496/CTNNB1 to activate Wnt pathway

Background

Accumulating evidence has proved the significant influence of long non-coding RNAs (lncRNAs) in cancer formation and development, including PCa.

Methods

The role of LINC00689 in PCa was confirmed by RT-qPCR, MTT, colony formation, flow cytometry, western blot and transwell assays. Besides, the binding ability between LINC00689 and miR-496 was validated by using luciferase reporter assay. Then RT-qPCR, RIP and luciferase reporter and western blot assays were employed to verify the interactions among LINC00689, miR-496 and CTNNB1. Furthermore, the rescuing role of CTNNB1 in Wnt pathway was proved by RT-qPCR, TOP/FOP Flash and western blot assays.

Results

LINC00689 was upregulated in PCa tissues and cells as well as at the terminal stage. Further, knock down of LINC00689 repressed PCa cell proliferation, migration and invasion, and initiated PCa cell apoptosis. Additionally, miR-496 inhibitor and pcDNA3.1/CTNNB1 could neutralize the prohibitive effects of LINC00689 silencing on cell proliferation, migration and invasion, meanwhile, could offset the encouraging role of knocking down LINC00689 in cell apoptosis. Moreover, CTNNB1 upregulation exerted redemptive function in Wnt pathway inhibited by LINC00689 depletion.

Conclusions

To sum up, LINC00689 promotes PCa progression via regulating miR-496/CTNNB1 to activate Wnt pathway, which may contribute to research about new targets for PCa treatment.

Rab23 contributes to the progression of colorectal cancer via protein kinase B and extracellular signal-regulated kinase signaling pathways

The role of Ras-related protein Rab23 in tumors has attracted increasing attention in recent years; however, whether it can function as an oncogenic protein remains under debate, and its role in colorectal cancer (CRC) is currently unknown. In the present study, high expression of Rab23 in CRC tissues was confirmed using immunohistochemistry, and high expression of Rab23 in CRC cells (SW1116 and HT29) was confirmed using reverse transcription-polymerase chain reaction and western blot analysis. A positive association of Rab23 with tumor size and advanced clinical stage was confirmed by χ² analysis. In addition, the positive association of Rab23 with poor disease-free survival was confirmed by survival analysis. Cell experiments further demonstrated that overexpression of Rab23 increased the expression of the proliferation marker Ki-67 and the proliferative ability in SW1116 and HT29 cells. Molecular mechanism research revealed that the extracellular signal-regulated kinase (ERK) and protein kinase B (AKT) signaling pathways contributed to the high expression of Ki-67 and increased the proliferative ability induced by Rab23 in CRC cells. In conclusion, the study confirmed the high expression of Rab23 in CRC, and its positive association with CRC progression and poor prognosis. Furthermore, the data demonstrated that Rab23 increased the proliferation of CRC cells via the ERK and AKT signaling pathways. These results suggest that Rab23 may be used as a protein for diagnosis and prognosis prediction in patients with CRC, and is proposed to be a novel therapeutic target for improving the patient outcome.

Circular RNA MYLK promotes hepatocellular carcinoma progression by increasing Rab23 expression by sponging miR-362-3p

Background

CircRNA myosin light chain kinase (circRNA MYLK) has been shown to promote the progression of various tumor diseases. The purpose of this study was to explore the potential molecular mechanism of circMYLK in hepatocellular carcinoma (HCC).

Methods

The quantitative Real-Time PCR (qRT-PCR) was used to measure the expressions of circMYLK, miR-362-3p and Rab23 in HCC tissues and cell lines. Huh7 and Hep3B cells were selected to explore the role of circMYLK in proliferation, invasion and migration of HCC cells in vitro. The interaction among circMYLK, miR-362-3p and Rab23 was investigated by biological information and dual luciferase gene reporter assay. The effect of circMYLK on HCC tumor growth in vivo was studied in a tumor xenograft model in mice.

Results

CircMYLK was highly expressed in HCC tissues and cell lines, which was associated with poor prognosis in HCC patients. In addition, knockdown of circMYLK remarkably inhibited the proliferation, invasion, and migration of Huh7 and Hep3B cells. MiR-362-3p was a direct target of circMYLK, and Rab23 was a direct target gene of miR-362-3p. Meanwhile, circMYLK was negatively correlated with the expression of miR-362-3p and positively correlated with Rab23 expression. Moreover, either overexpressed miR-362-3p or silencing Rab23 could observably suppress the enhanced proliferation, invasion, and migration induced by circMYLK in Huh7 and Hep3B cells. Finally, knockdown of circMYLK and overexpressed miR-362-3p could suppress the expression of Rab23, thus inhibiting the growth and proliferation of Hep3B cells in vivo.

Conclusion

circMYLK promotes the occurrence and development of HCC by regulating the miR-362-3p/Rab23 axis, which provides a novel direction and theoretical basis for the early diagnosis and treatment of HCC.

Inhibiting geranylgeranyl diphosphate synthesis reduces nuclear androgen receptor signaling and neuroendocrine differentiation in prostate cancer cell models

BACKGROUND

Following androgen deprivation for the treatment of advanced adenocarcinoma of the prostate, tumors can progress to neuroendocrine prostate cancer (NEPC). This transdifferentiation process is poorly understood, but trafficking of transcriptional factors and/or cytoskeletal rearrangements may be involved. We observed the role of geranylgeranylation in this process by treatment with digeranyl bisphosphonate (DGBP), a selective inhibitor of geranylgeranyl pyrophosphate synthase which blocks the prenylation of small GTPases such as Rho and Rab family proteins, including Cdc42 and Rac1.

METHODS

We examined the therapeutic potential of DGBP in LNCaP, C4-2B4, and 22Rv1 cell culture models. Cell morphology and protein expression were quantified to observe the development of the neuroendocrine phenotype in androgen-deprivation and abiraterone-treated LNCaP models of NEPC development. Luciferase reporter assays were utilized to examine AR activity, and immunofluorescence visualized the localization of AR within the cell.

RESULTS

Essential genes in the isoprenoid pathway, such as HMGCR, MVK, GGPS1, and GGT1, were highly expressed in a subset of castration resistant prostate cancers reported by Beltran et al. Under treatment with DGBP, nuclear localization of AR decreased in LNCaP, 22Rv1, and C4-2B4 cell lines, luciferase reporter activity was reduced in LNCaP and 22Rv1, and AR target gene transcription also decreased in LNCaP. Conversely, nuclear localization of AR was enhanced by the addition of GGOH. Finally, induction of the NEPC structural and molecular phenotype via androgen deprivation in LNCaP cells was inhibited by DGBP in a GGOH-dependent manner.

CONCLUSIONS

DGBP is a novel compound with the potential to reduce AR transcriptional activity and inhibit PCa progression to NEPC phenotype. These results suggest that DGBP may be used to block cell growth and metastasis in both hormone therapy sensitive and resistant paradigms.

miR-338-3p targets RAB23 and suppresses tumorigenicity of prostate cancer cells

MicroRNA-338-3p (miR-338-3p) has been implicated in several cancers; however, its role in human prostate cancer remains unknown. In this study, we observed downregulation of miR-338-3p in prostate cancer tissues and cell lines. Forced expression of miR-338-3p suppressed prostate cancer cell proliferation, migration, and invasion in vitro and tumor growth in vivo, while apoptosis was induced. Further experiments revealed that RAB23 is a target of miR-338-3p because miR-338-3p bound directly to the 3'-untranslated region (3'-UTR) of RAB23 mRNA, thereby reducing both the mRNA and protein levels of RAB23. Reintroduction of RAB23 attenuated the inhibitory effects of miR-338-3p on proliferation, migration, and invasiveness of prostate cancer cells. In clinical samples, miR-338-3p levels negatively correlated with RAB23 expression, which was upregulated in prostate cancer. Collectively, these results indicate that miR-338-3p acts as a tumor suppressor in prostate cancer by directly targeting RAB23.

RAB31 Targeted by MiR-30c-2-3p Regulates the GLI1 Signaling Pathway, Affecting Gastric Cancer Cell Proliferation and Apoptosis

Background: Gastric cancer (GC), one of the most common cancers worldwide, is highly malignant and fatal. Ras-related protein in brain 31 (RAB31), a member of the RAB family of oncogenes, participates in the process of carcinogenesis and cancer development; however, its role in GC progression is unknown.

Methods: In our study, 90 pairs of tissue microarrays were used to measure the levels of RAB31 protein by immunochemistry, and 22 pairs of fresh tissue were used to measure the levels of RAB31 mRNA by quantitative PCR. We also investigated the effects of RAB31 on tumor growth both in vitro and in vivo.

Results: RAB31 was overexpressed in GC tissues, and its overexpression predicted poor survival in patients. In a nude mouse model, depletion of RAB31 inhibited tumor growth. In vitro, silencing of RAB31 suppressed cell viability, promoted cell cycle arrest, enhanced apoptosis, and affected the expression of cell cycle and apoptotic proteins; these effects were mediated by glioma-associated oncogene homolog 1 (GLI1). Co-immunoprecipitation and immunofluorescence assays confirmed that RAB31 interacted with GLI1. In addition, luciferase reporter assays and Western blotting showed that microRNA-30c-2-3p modulated the RAB31/GLI1 pathway by targeting the 3′-untranslated region of RAB31.

Conclusions: Collectively, these data show that RAB31 is regulated by microRNA-30c-2-3p, and functions as an oncogene in GC tumorigenesis and development by interacting with GLI1. Therefore, targeting the miR-30c-2-3p/RAB31/GLI1 axis may be a therapeutic intervention for gastric cancer.

Rab23 and developmental disorders

Rab23 is a conserved member of the Rab family of small GTPases that regulates membrane trafficking in eukaryotes. It is unique amongst the Rabs in terms of its implicated role in mammalian development, as originally illustrated by the embryonic lethality and open neural tube phenotype of a spontaneous mouse mutant that carries homozygous mutation of open brain, a gene encoding Rab23. Rab23 was initially identified to act as an antagonist of Sonic hedgehog (Shh) signaling, and has since been implicated in a number of physiological and pathological roles, including oncogenesis. Interestingly, RAB23 null allele homozygosity in humans is not lethal, but instead causes the developmental disorder Carpenter’s syndrome (CS), which is characterized by craniofacial malformations, polysyndactyly, obesity and intellectual disability. CS bears some phenotypic resemblance to a spectrum of hereditary defects associated with the primary cilium, or the ciliopathies. Recent findings have in fact implicated Rab23 in protein traffic to the primary cilium, thus linking it with the primary cellular locale of Shh signaling. Rab23 also has Shh and cilia-independent functions. It is known to mediate the expression of Nodal at the mouse left lateral plate mesoderm and Kupffer’s vesicle, the zebrafish equivalent of the mouse node. It is thus important for the left-right patterning of vertebrate embryos. In this review, we discuss the developmental disorders associated with Rab23 and attempt to relate its cellular activities to its roles in development.

Rab23 promotes the cisplatin resistance of ovarian cancer via the Shh-Gli-ABCG2 signaling pathway

As a novel member of the Rab GTPase family, the role of Rab23 has been reported in multiple types of tumor. However, to the best of our knowledge, the role of Rab23 in ovarian cancer (OC) has not yet been reported. In the present study, immunohistochemistry analysis demonstrated that Rab23 was upregulated in OC tissue; survival analysis indicated that Rab23 expression was associated with a reduced overall survival (OS) rate and disease-free survival (DFS) time. In vitro experiments also demonstrated the increased expression of Rab23 in the OC cells lines, A2780 and SKOV-3, compared with in the normal ovarian cell line, IOSE80. Following the silencing of ABCG2 in SKOV-3 cells, ATP-binding cassette sub-family G member 2 (ABCG2) expression was significantly downregulated both at the RNA and protein levels. The cisplatin (DDP) IC₅₀ declined from 43.09±7.12 µmol/l in control cells to 26.46±5.38 µmol/l in SKOV-3 cells with silenced Rab23. In contrast, in A2780 cells overexpressing Rab23 (A2780-Rab23), ABCG2 expression was significantly upregulated and the DDP IC₅₀ increased from 27.42±6.54 µmol/l in control cells to 45.92±5.23 µmol/l in A2780-Rab23. Investigation into the potential molecular mechanisms for this revealed that the expression of sonic hedgehog (Shh) and Gli family zinc finger 1 (Gli1) was increased in A2780-Rab23 cells, whereas silencing Rab23 in SKOV-3 cells significantly inhibited the expression of Shh and Gli1. The Gli1 inhibitor GANT-61 significantly abrogated the increased ABCG2 expression in A2780-Rab23 cells. Furthermore, the DDP IC₅₀ in A2780-Rab23 cells decreased significantly following the silencing of ABCG2 expression; the IC₅₀ declined from 51.66±8.32 µmol/l in A2780-Rab23 cells to 25.61±6.17 µmol/l in A2780-Rab23 cells with silenced ABCG2. Collectively, the results indicate that Rab23 promotes the DDP resistance of OC cells via the Shh-Gli1-ABCG2 pathway, providing the proof of principle for the further investigation of drug resistance therapy targeting Rab23.

microRNA-323 upregulation promotes prostate cancer growth and docetaxel resistance by repressing p73

Our previous work has demonstrated that miR-323 enhances tumor angiogenesis in prostate cancer. In the present study, we sought to determine the function of miR-323 in prostate cancer cell growth and response to docetaxel. The effects of miR-323 overexpression on prostate cancer cell proliferation, colony formation, and tumorigenesis were examined. We also investigated the impact of miR-323 knockdown on cell cycle progression and apoptosis. Ectopic expression of miR-323 promoted cell proliferation and colony formation in vitro and xenograft tumor growth in vivo. Depletion of miR-323 arrested PC-3 prostate cancer cells at the G0/G1 phase and caused significant apoptosis, which was coupled with increased expression of p21 and cleavage of caspase-9 and caspase-3 and reduced expression of cyclin D1. Compared to PC-3 parental cells, docetaxel-resistant PC-3-DR cells had 5.6-fold higher levels of miR-323. Overexpression of miR-323 increased the 50% inhibitory concentration (IC₅₀) value for docetaxel in PC-3 cells, while silencing of miR-323 exerted an opposite effect on PC-3-DR cells. Mechanistically, miR-323 repressed the expression of p73 in prostate cancer cells. Knockdown of p73 augmented cell proliferation and colony formation and blunted sensitivity to docetaxel in PC-3 cells. In addition, overexpression of p73 significantly suppressed cell proliferation and induced apoptosis and docetaxel sensitivity in PC-3-DR cells. In conclusion, miR-323 contributes to the aggressive phenotype of prostate cancer cells by targeting p73 and represents a potential therapeutic target for this malignancy.