Table 2.

Summary of piRNAs showing pan-cancer expression patterns.

piRNA	Cancer	Expression	Related gene	Mechanical points	Clinical Utility	Sample Type					Detection Technique	Reference
						TCGA	Tissue	cell	serum	mice
piR-651	Breast cancer	↑	Estrogen and Androgen	Modulated by estrogen and androgen hormone levels	Theraputic	no	no	yes	no	no	RT-PCR	114
		↑	–	–	Diagnostic	no	yes	yes	no	no	piRNA microarrayRT-PCR	115
	Cervical cancer	↑	–	–	Diagnostic	no	no	yes	no	no	piRNA microarrayRT-PCR	115
	Gastric cancer	↓	–	The piR-651 level in gastric adenocarcinoma was higher than that in gastric signet ring cell carcinoma.	Diagnostic Theraputic	no	no	no	yes	no	RT-PCR	116
		↑	–	Promote cancer cell growth	Diagnostic	no	no	yes	no	no	piRNA microarrayRT-PCR	115
	Hodgkin lymphoma	↓	–	–	Diagnostic	no	yes	yes	yes	no	RT-PCR	117
	Liver cancer	↑	–	–	Diagnostic	no	no	yes	no	no	piRNA microarrayRT-PCR	115
	Lung cancer	↑	Caspase-3-p17, cleaved-PARP-1, Bcl-2	piR651 inhibitor induced cell apoptosis, with caspase-3-p17 and cleaved-PARP-1 increased, whereas Bcl-2 expression decreased	Diagnostic	no	no	yes	no	no	RT-PCR	118
		↑	–	–	Diagnostic	no	no	yes	no	no	piRNA microarrayRT-PCR	115
		↑	Cyclin D1 and CDK4	piR-651 induces NSCLC progression through the cyclin D1 and CDK4 pathway	Diagnostic Theraputic	no	yes	yes	no	yes	RT-PCR	119
		↑	–	promote cell proliferation, apoptosis, migration and invasion	Theraputic	no	no	yes	no	no	RT-PCR	120
	Mesothelium	↑	–	–	Diagnostic	no	no	yes	no	no	piRNA microarrayRT-PCR	115
	Prostate cancer	↑	Estrogen and Androgen	Modulated by estrogen and androgen hormone levels	Theraputic	no	no	yes	no	no	RT-PCR	114
piR-823	Breast cancer	↑	Estrogen and Androgen	Modulated by estrogen and androgen hormone levels	Theraputic	no	no	yes	no	no	RT-PCR	114
	Colorectal cancer	↑	HSF1 (heat shock protein (HSP) 27, 60, 70)	Upregulate phosphorylation and transcriptional activity of HSF1	Theraputic	no	yes	yes	no	no	RT-PCR	121
	Gastric cancer	↓	–	The piR-823 level was positively associated with tumor-node-metastasis stage and distant metastasis.	Diagnostic Theraputic	no	no	no	yes	no	RT-PCR	116
		↓	–	Inhibited cell growth in vitro and in vivo.	Theraputic	no	yes	yes	no	yes	piRNA microarray RT-PCR	122
	Kidney cancer	↑/↓	–	piR-823 is down-regulated in tumor tissue, but positively correlated with worse outcome, indicating its complex role in RCC pathogenesis (↑blood serum and urine↓tumor tissue)	Diagnostic	no	yes	no	yes	no	RT-PCR	123
	Liver cancer	↑		Gradually increased from cirrhosis to low- and high-grade dysplastic nodules and to hepatocellular carcinoma (HCC)	Diagnostic	no	no	yes	no	no	RT-PCR	55
	Multiple myeloma	↑	VEGF, IL-6, ICAM-1, CXCR4, Bax, Bcl2	Promoted cell proliferation, tube formation, and invasion by enhancing VEGF, IL-6, ICAM-1, CXCR4 and attenuating apoptosis. (inhibition of Caspase-3 activation, downregulation of Bax, and upregulation of Bcl2) and production of ROS and NO	Prognostic Therapeutic	no	no	yes	yes	yes	RT-PCR	20
		↑	DNMT3B	Myeloid-derived suppressor cells confer stem-like qualities to multiple myeloma cells by upregulating piRNA-823 expression and activating DNMT3B activation	Theraputic	no	yes	yes	no	yes	RT-PCR	83
		↑	DNMT3A and 3B, p16INK4A	induce de novo DNA methyltransferases, DNMT3A and 3B and inhibit methylation-silenced tumor suppressor, p16INK4A.	Theraputic	no	yes	yes	no	no	RT-PCR	124
	Prostate cancer	↑	Estrogen and Androgen	Modulated by estrogen and androgen hormone levels	Theraputic	no	no	yes	no	no	RT-PCR	114
piR-4987	Breast cancer	↑	–	Up-regulated piR-4987 expression was associated with lymph node positivity	Prognostic	no	yes	no	no	no	piRNA microarray RT-PCR	88
	Multiple myeloma	↑	–	Upregulated in stage III MM patients compared with healthy individuals	Diagnostic	no	yes	no	no	no	RT-PCR	124
piR-Hep1	Liver cancer	↑	AKT	Promotes cell viability, motility, and invasiveness by activation of AKT phosphorylation	–	no	yes	yes	no	no	RT-PCR	97
	Multiple myeloma	↑	–	Upregulated in stage III MM patients compared with healthy individuals	Diagnostic	no	yes	no	no	no	RT-PCR	124
piR-39980	Fibrosarcoma	↓	RRM2	piR-39980 promotes apoptosis and inhibits proliferation by repressing RRM2 through direct targeting at its 3′-UTR through extensive sequence complementary binding	Therapeutic	no	no	yes	no	no	RT-PCR	108
	Neuroblastoma	↑	JAK3	Inhibition of piRNA induces NB cells senescence by modulating JAK3 through target binding. piR-39980 desensitizes the effect of doxorubicin and inhibit drug-induced apoptosis.	Theraputic	no	no	yes	no	no	piRNA profiling RT-PCR	127

Abbreviation: BCL2, BCL2 apoptosis regulator; CDK4, Cyclin dependent kinase 4; CXCR4, C-X-C motif chemokine receptor 4; DNMT, DNA methyltransferase; JAK3, Janus kinase 3; HSP, heat shock protein; HSF1, heat shock transcription factor 1; VEGF, vascular endothelial growth factor; IL6, interleukin 6; ICAM1, intercellular adhesion molecule 1; MM, Multiple myeloma; RRM2, ribonucleotide reductase regulatory subunit M2; RT-PCR, quantificational real time-polymerase chain reaction; TCGA, The Cancer Genome Atlas; UTR, untranslated region.