INXS, um longo RNA não codificador de proteínas mediador da apoptose / INXS, a long noncoding RNA that mediates apoptosis

O splicing alternativo do pré-mRNA de BCL-X produz duas isoformas de mRNAs com funções antagônicas, a pró-apoptótica BCL-XS e a anti-apoptótica BCL-XL, cujo balanço regula a homeostasia celular. Entretanto, o mecanismo que regula esse processamento ainda é desconhecido. Nesse trabalho, nós identificamos e caracterizamos um longo RNA não codificador de proteínas (lncRNA) nomeado INXS, que é transcrito a partir da fita oposta do locus genômico de BCL-X, sendo menos abundante em linhagens celulares tumorais e tecidos tumorais de pacientes quando comparados com os respectivos pares não tumorais. INXS é um RNA unspliced de 1903 nts, é transcrito pela RNA Polimerase II, possui cap 5', está enriquecido na fração nuclear das células e se liga à proteína Sam68 do complexo modulador de splicing. O tratamento de células tumorais 786-O com cada um de três agentes indutores de apoptose aumentou a expressão endógena do INXS, levando ao aumento expressivo da proporção entre os mRNAs de BCL-XS / BCL-XL, e ativação das caspases 3, 7 e 9. Estes efeitos foram anulados na presença do knockdown do INXS. Da mesma forma, a superexpressão ectópica do INXS causou uma mudança no splicing favorecendo a isoforma BCL-XS e ativação das caspases, aumentando os níveis da proteína BCL-XS e conduzindo as células à apoptose. Utilizando um modelo in vivo, cinco injeções intra-tumorais do INXS durante 15 dias causaram uma regressão acentuada no volume dos xenotumores. Portanto, INXS é um lncRNA que induz a apoptose, sugerindo que essa molécula seja um possível alvo a ser explorado na terapia contra o câncer

BCL-X mRNA alternative splicing generates pro-apoptotic BCL-XS or anti-apoptotic BCL-XL, whose balance regulates cell homeostasis. However, the mechanism that regulates the splice shifting is incompletely understood. Here, we identified and characterized a long noncoding RNA (lncRNA) named INXS, transcribed from the opposite genomic strand of BCL-X, that was less abundant in tumor cell lines and patient tumor tissues compared with non-tumors. INXS is an unspliced 1903 nt-long RNA, is transcribed by RNA Polymerase II, 5'-capped, nuclear enriched and binds Sam68 splicing-modulator. The treatment of tumor cell line 786-O with each of three apoptosis-inducing agents increased endogenous INXS lncRNA, increased BCL-XS / BCL-XL mRNA ratio, and activated caspases 3, 7 and 9. These effects were abrogated in the presence of INXS knockdown. Similarly, ectopic INXS overexpression caused a shift in splicing towards BCL-XS and activation of caspases, increasing the levels of BCL-XS protein and then leading the cells to apoptosis. In a mouse xenograft model, five intra-tumor injections of INXS along 15 days caused a marked regression in tumor volume. INXS is an lncRNA that induces apoptosis, suggesting that INXS is a possible target to be explored in cancer therapies

Expression of TRF2 and its prognostic relevance in advanced stage cervical cancer patients

BACKGROUND: Telomeres are protective caps consisted of specific tandem repeats (5'-TTAGGG-3'). Shortening of telomeres at each cell division is known as "mitotic clock" of the cells, which renders telomeres as important regulators of lifespan. TRF2 is one of the critical members of shelterin complex, which is a protein complex responsible from the preservation of cap structure, and loss or mutation of TRF2 results in DNA damage, senescence or apoptosis. Since cancer is frequently associated with aberrant cell cycle progression, defective DNA repair or apoptosis pathways, TRF2 could be one likely candidate for cancer therapy. Here we investigated the prognostic role of TRF2 levels in cervical cancer patients. Fold-induction rates were evaluated with respect to median values after real-time PCR analysis. Overall survival, distant disease-free and local recurrence-free survival rates were calculated using Kaplan-Meier long rank test. RESULTS: Both five year overall- and disease-free survival rates were longer in patients with higher TRF2 expression compared to lower expression, but results were not statistically significant (69.2% vs 28.9%, respectively). Mean local recurrence-free survivals (LRF) were very close ( 58.6, CI: 44.3-72.9 vs 54.5, CI: 32.1-76.9 months) for high and low expressions, respectively. Cumulative proportion of LRF at the end of five year period was 76.9% for high and 57.1% for low TRF2 expression (P = 0.75). Statistically significant difference was found between survival ratios and Bcl-xL and p53 gene expressions, but not with TRF2. A respectable correlation between TRF2 expression and apoptosis along with distant metastasis was noted (P = 0.045 and 0.036, respectively). Additionally, high TRF2 expression levels had a positive impact in five year survival rate of stage IIIB-IVA patients (P = 0.04). CONCLUSIONS: Our results support the role of TRF2 in apoptosis and imply a positive relation with distant metastases and survival in advanced stage patients. The remarkable difference in survival periods of patients with different TRF2 expressions suggest that TRF2 may be a candidate factor to estimate survival for cervical cancer, a preliminary observation which should further be verified with a larger cohort.