Ancient pathways of an apoptosis-like cell death have been identified in unicellular eukaryotes including protozoan parasites. Here, we examined programmed cell death in the apicomplexan Toxoplasma gondii which is a common intracellular pathogen of humans and warm-blooded animals. Treatment of extracellular T. gondii with various pro-apoptotic stimuli significantly induced DNA strand breaks as revealed by TUNEL and flow cytometry. Using staurosporine or miltefosine as pro-apoptotic stimuli, parasites also presented a reduced cell size, i.e. pyknosis and externalized phosphatidylserine while the plasma membrane remained intact. Importantly, staurosporine also induced DNA strand breaks in intracellular T. gondii. Data mining of the Toxoplasma genome resource identified 17 putative cell death-associated genes encoding proteases, a nuclease and several apoptosis regulators. Staurosporine-treated parasites but not controls strongly up-regulated several of these genes in a time-dependent fashion with a putative PDCD2 protein being more than 100-fold up-regulated. However, the mitochondrial membrane potential (ΔΨm) remained intact and caspase-like activity increased only slightly during staurosporine-triggered cell death. As compared to staurosporine, the transcriptional response of parasites to miltefosine was more restricted but PDCD2 was again strongly induced. Furthermore, T. gondii lost their ΔΨm and rapidly presented strong caspase-like activity during miltefosine treatment. Consequently, protease inhibitors abrogated miltefosine-induced but not staurosporine-induced Toxoplasma cell death. Finally, toxoplasmacidal drugs triggered DNA strand breaks in extracellular T. gondii. Interestingly, clindamycin also induced markers of an apoptosis-like cell death in intracellular parasites. Together, the data indicate that T. gondii possesses ancient apoptosis-like cell death machinery which can be triggered by chemotherapeutic agents.

Mutations in the KRAS (Kirsten rat sarcoma viral oncogene homolog gene) and BRAF (v‐Raf murine sarcoma viral oncogene homolog B1) gene play a significant role in primary resistance to colorectal cancer therapy. Around 85‐90% of KRAS mutations in colorectal cancer occur in exon 2 (codon 12 and 13), whereas approximately 96% of BRAF mutations occur in exon 15 codon 600 (V600E). This study aimed to determine the prevalence and mutation characteristics of the KRAS and BRAF genes in colorectal cancer patients in Bali. The DNA was isolated from 44 formalin‐fixed paraffin‐embedded colorectal cancer samples which were stored in the Department of Pathology, Sanglah General Hospital in 2017. Detection of mutation was carried out by polymerase chain reaction (PCR) and direct sequencing. Out of 44 samples, only 27 were successfully amplified and sequenced. Our findings showed six samples (22.2%) with mutated KRAS at codons 12 and 13 (including two samples with G12D, one sample with G12V, and three samples with G13D). Interestingly, we found three samples (11.1%) of BRAF mutation, including two samples with V600E mutation and one with V600L mutation. Taken together, our results showed that KRAS and BRAF mutations were identified and occurred exclusively. Further studies are essential to identify the correlation of these mutations with colorectal cancer prognosis and response to chemotherapy

Kanker kolorektal merupakan masalah kesehatan di dunia. Perkembangan kanker kolorektal memerlukan waktu panjang dan berkaitan dengan faktor lingkungan, genetik dan epigenetik. Patogenesis kanker kolorektal melibatkan tiga jalur yang seringkali tumpang tindih yaitu chromosomal instability (CIN), microsatellite instability (MSI) dan CpG island methylator phenotype (CIMP). Dalam tulisan ini dibahas mengenai kanker kolorektal herediter dan sporadik serta aspek genetiknya. Pemahaman mengenai aspek genetik kanker kolorektal sangat berperan dalam manajemen penyakit ini.

No abstract