pfeRNAs-A Novel Class of Small Non-coding RNAs With Real Translational Potential

Small non-coding RNAs (sncRNAs) are defined by being less than 200 nucleotides (nt) in length, and consequently, have been divided into many different subclasses including mature microRNA (miRNA), small interfering RNA (siRNA), piwi-interacting RNA (piRNA), protein functional effector sncRNA (pfeRNA), precursor miRNA (pre-miRNA), small nucleolar RNA (snoRNA), 5S ribosome RNA (5SrRNA), 5.8SrRNA, and small nuclear RNA (snRNA). Except for the class of pfeRNAs, the discovery, identification, biogenesis, characterization, and function of other sncRNAs have been well documented. Herein, we provide a review, written especially for clinicians, of the least understood class of functional sncRNAs, the pfeRNAs, focusing on their initial discovery, identification, unique features, function, as well as their exciting clinical translational potential.

Abstract 271: Monitoring of CCR2 and CCR5 expression on circulating myeloid derived suppressor cells (MDSCs) in non-small cell lung cancer as a correlate of minimum residual disease

Objectives: Myeloid derived suppressor cells (MDSCs) are immature cells that aid in cancer progression and dissemination via immune system suppression. Previous work has shown that CCR 2 (C-C chemokine receptor) and CCR 5 expression on MDSCs is increased in non-small cell lung cancer (NSCLC). We hypothesized that patients with lung cancer will have detectable peripheral MDSCs with CCR2 and CCR5 expression preoperatively, that it would decrease immediately postoperatively, and then increase longitudinally if tumor recurs.

Materials & Methods: As part of a prospective longitudinal study, whole blood samples were obtained from patients suspected to have primary lung cancer prior to surgery. Patients were excluded if they were minors, could not provider consent, had malignancy within the past 10 years or any immunosuppressive condition. Blood samples were obtained prior to surgery or at follow-up in clinic and processed within 1 hour of acquisition. We stained samples via 2 different methods: 1) whole blood and 2) peripheral blood mononuclear cells (PBMC) extracted from Ficoll density gradient and determined that whole blood staining had superior results. Samples were analyzed via flow cytometer and gated after defining MO (monocytic)-MDSCs as CD33+HLADRlow/-CD14+ and PMN-MDSCs as CD33+HLADR-CD15+. MDSCs were reported as a percentage of live leukocytes and means were reported with T-test performed for statistical analysis.

Results: A total of 18 patients were recruited with a median age of 69 years (63.8-75) and 61% (11/18) females. Adenocarcinoma was present in 16, carcinoid tumor in 1 and both adenocarcinoma and carcinoid tumor in 1 patient. Stage I and Stage II were the most common (66.7% and 22.2%, respectively). Majority of the tumors were in the right upper lobe (55.6%). There were 7 healthy controls with a median age of 29 years (28-43) and 71% females. There was a significantly increased proportion of MO-MDSCs in NSCLC patients preoperatively compared to healthy controls (11.64% versus 5.02%, p = 0.02). CCR2+CCR5+ MO-MDSCs were 0.85% in patients versus 0.06% in controls (p=0.04). No differences were noted with PMN-MDSCs. Five patients had post-operative follow up (mean 152 days) with an average decrease of 63% in MO-MDSCs, 68% in CCR2+CCR5+ MO-MDSCs and no recurrence of tumor on CT scans.

Conclusion: Early results of this on-going study demonstrate the detection of circulating CCR2+CCR5+ MO-MDSCs in the preoperative whole blood of NSCLC patients compared to healthy controls. Resection of the tumor is associated with a decrease of these MO-MDSCs after treatment. We are evaluating if any increase in CCR2+CCR5+ MO-MDSC in long term will allow us to use it as an adjuvant tool along with CT monitoring as a biomarker of residual or recurrent disease.

Citation Format: Hamza Khan, Anas Awan, Maria Shishikura, Carley Blevins, Kristen Rodgers, Yuping Mei, Wasay Nizam, Shun Ishiyama, Yun Chen, Richard Battafarano, Errol Bush, Stephen Broderick, Stephen Yang, Hajime Orita, Peng Huang, Ada Tam, Jinny Ha, Franck Housseau, Malcolm Brock. Monitoring of CCR2 and CCR5 expression on circulating myeloid derived suppressor cells (MDSCs) in non-small cell lung cancer as a correlate of minimum residual disease [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 271.

Expression of receptor protein tyrosine phosphatase δ, PTPδ, in mouse central nervous system

Protein tyrosine phosphate δ (PTPδ), one of the receptor type IIa protein tyrosine phosphates, is known for its roles in axon guidance, synapse formation, cell adhesion, and tumor suppression. Alternative splicing of this gene generates at least four (A-D) isoforms; however, the major isoform in vivo is yet to be determined. The protein localization has neither been revealed. We have generated anti-mouse PTPδ-specific monoclonal antibody and analyzed the protein expression in wild-type and Ptpδ knockout mice. Immunoblot analysis of various organs revealed that neuronal tissues express both C-and D-isoforms of PTPδ, whereas non-neuronal tissues express only C-isoform. Immunohistochemistry of wild-type or Ptpδ heterozygous sections showed that olfactory bulb, cerebral cortex, hippocampus, cerebellum, and several nuclei in brain stem exhibit moderate to strong positive signals. These signals were absent in Ptpδ knockout specimens. Higher magnification revealed differences between expression patterns of PTPδ mRNA and its protein product. In hippocampus, weak mRNA expression in CA1 stratum pyramidale but strong immunostaining in the stratum lacunosum moleculare was observed, suggesting the axonal expression of PTPδ in the entorhinal cortical afferents. Olfactory mitral cells exhibited mRNA expression in cell bodies and protein localization in their dendritic fields, glomerular and external plexiform layers. Nissl staining showed that the external plexiform layer was reduced in Ptpδ knockout mice. Golgi-impregnation confirmed the poor dendritic growth of homozygous mitral cells. These results suggest that PTPδ may localize in axons as well as in dendrites to regulate their elaboration in the central nervous system.