Organismal and Cellular Stress Responses upon Disruption of Mitochondrial Lonp1 Protease.

Cells engage complex surveillance mechanisms to maintain mitochondrial function and protein homeostasis. LonP1 protease is a key component of mitochondrial quality control and has been implicated in human malignancies and other pathological disorders. Here, we employed two experimental systems, the worm Caenorhabditis elegans and human cancer cells, to investigate and compare the effects of LONP-1/LonP1 deficiency at the molecular, cellular, and organismal levels. Deletion of the lonp-1 gene in worms disturbed mitochondrial function, provoked reactive oxygen species accumulation, and impaired normal processes, such as growth, behavior, and lifespan. The viability of lonp-1 mutants was dependent on the activity of the ATFS-1 transcription factor, and loss of LONP-1 evoked retrograde signaling that involved both the mitochondrial and cytoplasmic unfolded protein response (UPRmt and UPRcyt) pathways and ensuing diverse organismal stress responses. Exposure of worms to triterpenoid CDDO-Me, an inhibitor of human LonP1, stimulated only UPRcyt responses. In cancer cells, CDDO-Me induced key components of the integrated stress response (ISR), the UPRmt and UPRcyt pathways, and the redox machinery. However, genetic knockdown of LonP1 revealed a genotype-specific cellular response and induced apoptosis similar to CDDO-Me treatment. Overall, the mitochondrial dysfunction ensued by disruption of LonP1 elicits adaptive cytoprotective mechanisms that can inhibit cancer cell survival but diversely modulate organismal stress response and aging.

PI3K/AKT pathway genetic alterations and dysregulation of expression in bladder cancer.

PURPOSE: To examine the involvement of specific components of the PI3K/AKT pathway in urinary bladder cancer development. METHODS: Samples from 65 tumors and 13 normal bladder tissues were collected. Genomic DNA isolation from snap-frozen and paraffin-embedded laser-microdissected tissues was followed by Sanger sequencing, whereas total RNA was purified for use in RT-PCR analyses. Immunohistochemistry was carried out on sections of paraffin-embedded biopsy material. RESULTS: Three pathogenic mutations (two missense and one frameshift) were identified in exon 20 of PIK3CA {c.3140A>G (p.His1047Arg), c.[3172A>T(;)3174C>T] (p.lle1058Phe), c.3203dupA (p.Asn1068Lysfs*5)} after laser capture microdissection, whereas PTEN mRNA expression was found to be downregulated in bladder cancer tissues compared to normal bladder urothelium. Upregulation of cytoplasmic and nuclear p-AKT expression was detected in low grade tumors, whereas in infiltrating carcinomas p-AKT was shown to be downregulated and confined to the cytoplasm. PTEN expression was weak and mainly cytoplasmic in superficial tumors, but stronger and nuclear in the infiltrating tumors. CONCLUSIONS: PI3K/AKT pathway activation is crucial for bladder cancer initiation and progression. In this context, PIK3CA, p-AKT and nuclear PTEN could be used along with other biomarkers for prognosis and selection of appropriate therapy in the clinical management of bladder cancer.

Gene-Specific Intron Retention Serves as Molecular Signature that Distinguishes Melanoma from Non-Melanoma Cancer Cells in Greek Patients.

BACKGROUND: Skin cancer represents the most common human malignancy, and it includes BCC, SCC, and melanoma. Since melanoma is one of the most aggressive types of cancer, we have herein attempted to develop a gene-specific intron retention signature that can distinguish BCC and SCC from melanoma biopsy tumors. METHODS: Intron retention events were examined through RT-sqPCR protocols, using total RNA preparations derived from BCC, SCC, and melanoma Greek biopsy specimens. Intron-hosted miRNA species and their target transcripts were predicted via the miRbase and miRDB bioinformatics platforms, respectively. Ιntronic ORFs were recognized through the ORF Finder application. Generation and visualization of protein interactomes were achieved by the IntAct and Cytoscape softwares, while tertiary protein structures were produced by using the I-TASSER online server. RESULTS: c-MYC and Sestrin-1 genes proved to undergo intron retention specifically in melanoma. Interaction maps of proteins encoded by genes being potentially targeted by retained intron-accommodated miRNAs were generated and SRPX2 was additionally delivered to our melanoma-specific signature. Novel ORFs were identified in MCT4 and Sestrin-1 introns, with potentially critical roles in melanoma development. CONCLUSIONS: The property of c-MYC, Sestrin-1, and SRPX2 genes to retain specific introns could be clinically used to molecularly differentiate non-melanoma from melanoma tumors.

Mutational analysis of TSC1 and TSC2 genes in Tuberous Sclerosis Complex patients from Greece.

Tuberous sclerosis complex (TSC) is a rare autosomal dominant disorder causing benign tumors in the brain and other vital organs. The genes implicated in disease development are TSC1 and TSC2. Here, we have performed mutational analysis followed by a genotype-phenotype correlation study based on the clinical characteristics of the affected individuals. Twenty unrelated probands or families from Greece have been analyzed, of whom 13 had definite TSC, whereas another 7 had a possible TSC diagnosis. Using direct sequencing, we have identified pathogenic mutations in 13 patients/families (6 in TSC1 and 7 in TSC2), 5 of which were novel. The mutation identification rate for patients with definite TSC was 85%, but only 29% for the ones with a possible TSC diagnosis. Multiplex ligation-dependent probe amplification (MLPA) did not reveal any genomic rearrangements in TSC1 and TSC2 in the samples with no mutations identified. In general, TSC2 disease was more severe than TSC1, with more subependymal giant cell astrocytomas and angiomyolipomas, higher incidence of pharmacoresistant epileptic seizures, and more severe neuropsychiatric disorders. To our knowledge, this is the first comprehensive TSC1 and TSC2 mutational analysis carried out in TSC patients in Greece.