Long Non-Coding Mitochondrial RNAs as Novel Molecular Target for Bladder Cancer Treatment

Bladder cancer (BC) is the sixth most common cause of cancer; BC risk increases with age and is more common among men than women. Upon diagnosis, the 5-year relative survival rate for patients is approximately 77%. The treatment options available for bladder cancer include chemotherapy, radiation therapy, immunotherapy, targeted therapy, and surgery. Despite the advances in therapeutically novel approaches, BC remains an important problem of public health. Long non-coding RNA (lncRNA) is defined as non-protein-coding RNA molecule longer than 200 nucleotides. Recent findings have highlighted that lncRNA contributes to the regulation of multiple signaling pathways in bladder cancer, suggesting that lncRNA exerts its roles during the biological processes of tumorigenesis, tumor proliferation, differentiation, apoptosis, invasion, migration, and stemness. In our laboratory, we described a family of mitochondrial long non-coding RNAs containing stem-loop structures, named sense and antisense. These transcripts are found outside the organelle, in the cytosol and nucleus in normal and tumor cells, and are differentially expressed according to proliferative status of cells. The antisense transcript seems to be a novel target for BC treatment based in modified antisense oligonucleotides. In this chapter, the novel biology and role of these RNAs as therapeutical targets will be discussed

Long Noncoding Mitochondrial RNAs (LncmtRNAs) as Targets for Cancer Therapy

Mitochondria are traditionally been viewed as the cell’s powerhouse, generating most of its ATP. However, besides this fundamental metabolic role, mitochondria are implicated in diverse other processes, including apoptosis, inflammation and metastasis. These functions are exerted in part by the growing class of long noncoding mitochondrial RNAs (lncmtRNAs). We found that normal human proliferating cells express a family of noncoding mitochondrial RNAs (ncmtRNAs), comprised of sense (SncmtRNA) and antisense (ASncmtRNA). However, tumor cells express only sense transcripts, suggesting that ASncmtRNA downregulation as a cancer new hallmark. The few ASncmtRNAs copies in tumor cells seem essential to tumor cell viability: knockdown of these transcripts with antisense oligonucleotides (ASO) causes massive apoptotic death of tumor cells, preceded by cell cycle arrest. Preclinical assays show that systemic administration of ASO delayed tumor growth in melanoma and renal cancer models and, caused total remission in subcutaneous renal cancer tumors. The same treatment, however, does not affect normal tissue, suggesting this approach for the development of an efficient and safe therapeutic strategy for several cancer types

Knockdown of Antisense Noncoding Mitochondrial RNA Reduces Tumorigenicity of Patient-Derived Clear Cell Renal Carcinoma Cells in an Orthotopic Xenograft Mouse Model

Clear cell renal cell carcinoma (ccRCC) is the most prevalent form of renal cancer and its treatment is hindered by a resistance to targeted therapies, immunotherapies and combinations of both. We have reported that the knockdown of the antisense noncoding mitochondrial RNAs (ASncmtRNAs) with chemically modified antisense oligonucleotides induces proliferative arrest and apoptotic death in tumor cells from many human and mouse cancer types. These studies have been mostly performed in vitro and in vivo on commercially available cancer cell lines and have shown that in mouse models tumor growth is stunted by the treatment. The present work was performed on cells derived from primary and metastatic ccRCC tumors. We established primary cultures from primary and metastatic ccRCC tumors, which were subjected to knockdown of ASncmtRNAs in vitro and in vivo in an orthotopic xenograft model in NOD/SCID mice. We found that these primary ccRCC cells are affected in the same way as tumor cell lines and in the orthotopic model tumor growth was significantly reduced by the treatment. This study on patient-derived ccRCC tumor cells represents a model closer to actual patient ccRCC tumors and shows that knockdown of ASncmtRNAs poses a potential treatment option for these patients

A putative RNA editing from U to C in a mouse mitochondrial transcript

Recently, we isolated and characterized a new mouse mitochondrial RNA molecule containing the mitochondrial 16S RNA plus 121 nt joined to the 5′ end of the RNA. This fragment arises from the L strand of the same gene and we have named this transcript chimeric RNA. At position 121 of the RNA there is a C, which, according to the sequence of the mitochondrial 16S RNA gene, should be a U. We hypothesized that this RNA is synthesized having a U at position 121, which is later substituted to a C by a putative editing reaction. Based on the presence of sites for the restriction endonucleases RsaI and Fnu4HI around position 121, both forms of the RNA were detected in mouse tissues. To confirm the presence of the non-edited and putative edited RNA, a fragment containing the first 154 nt of the RNA was amplified by RT–PCR and cloned. The substitution of U for C was demonstrated by sequencing these clones. In vitro transcription experiments demonstrated that the substitution of U for C is not due to artifact of amplification or cloning. Moreover, in mitochondria from testis only the non-edited form was found. This, together with other experimental evidence, demonstrated that the base substitution was not due to polymorphism of the mitochondrial 16S RNA gene. This is the first demonstration of a substitution reaction from U to C in a mammalian mitochondrial transcript

HPV-18 E2 protein downregulates antisense noncoding mitochondrial RNA-2, delaying replicative senescence of human keratinocytes

© Villota et al. Human and mouse cells display a differential expression pattern of a family of mitochondrial noncoding RNAs (ncmtRNAs), according to proliferative status. Normal proliferating and cancer cells express a sense ncmtRNA (SncmtRNA), which seems to be required for cell proliferation, and two antisense transcripts referred to as ASncmtRNA-1 and -2. Remarkably however, the ASncmtRNAs are downregulated in human and mouse cancer cells, including HeLa and SiHa cells, transformed with HPV-18 and HPV-16, respectively. HPV E2 protein is considered a tumor suppressor in the context of high-risk HPV-induced transformation and therefore, to explore the mechanisms involved in the downregulation of ASncmtRNAs during tumorigenesis, we studied human foreskin keratinocytes (HFK) transduced with lentiviral-encoded HPV-18 E2. Transduced cells displayed a significantly extended replicative lifespan of up to 23 population doublings, compared to 8 in control cells, together with downregulatio

Immunoresponse of Coho salmon immunized with a gene expression library from Piscirickettsia salmonis

We have used the expression library immunization technology to study the protection of Coho salmon Oncorhynchus kisutch to the infection with Piscirickettsia salmonis. Purified DNA from this bacterium was sonicated and the fragments were cloned in the expression vector pCMV-Bios. Two libraries were obtained containing 22,000 and 28,000 colonies and corresponding to approximately 8 and 10 times the genome of the pathogen, respectively. On average, the size of the inserts ranged between 300 and 1,000 bp. The plasmid DNA isolated from one of these libraries was purified and 20 µg were injected intramuscularly into 60 fish followed by a second dose of 10 µg applied 40 days later. As control, fish were injected with the same amount of DNA of the vector pCMV-Bios without insert. The titer of IgM anti-P. salmonis of vaccinated fish, evaluated 60 days post-injection, was significantly higher than that of the control group injected with the vector alone. Moreover, this response was specific against P. salmonis antigens, since no cross reaction was detected with Renibacterium salmoninarum and Yersinia ruckeri. The vaccinated and control fish were challenged 60 days after the second dose of DNA with 2.5 x 10(7) P. salmonis corresponding to 7.5 times the LD50. At 30 days post-challenge, 100% mortality was obtained with the control fish while 20% of the vaccinated animals survived. All surviving fish exhibited a lower bacterial load in the kidney than control fish. The expression library was also tested in Balb/c mice and it was found that the humoral immune response was specific to P. salmonis and it was dependent on the amount of DNA injecte

Production and immune response of recombinant Hsp60 and Hsp70 from the salmon pathogen Piscirickettsia salmonis

We have isolated and sequenced the genes encoding the heat shock proteins 60 (Hsp60) and 70 (Hsp70) of the salmon pathogen Piscirickettsia salmonis. The sequence analysis revealed the expected two open reading frames that encode proteins with calculated molecular weights of 60,060 and 70,400. The proteins exhibit a 70-80% homology with other known prokaryotic Hsp60 and Hsp70 sequences. The coding regions have been expressed in E. coli as thioredoxin fusion proteins. Both recombinant proteins were shown to elicit a humoral response when injected intraperitoneally in Atlantic salmon and also conferred protection to fish challenged with P. salmonis. The present data will facilitate further studies on the involvement of heat shock proteins in protective immunity of fish to infection by P. salmonis and their potential use in recombinants vaccines against this intracellular pathogen