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Ciklooksigenaze su ključni enzimi u biosintezi prostanoida. Postoje dvije izoforme: COX-1 koja je povezana s održavanjem fizioloških uvjeta u sluznici debelog crijeva; te inducibilna izoforma COX-2 koja je uglavnom povezana s patološkim procesima uključujući karcinom debelog crijeva. Cilj ovog istraživanja bio je ispitati ulogu COX izoformi u razvoju i napredovanju sporadičnoga karcinoma debeloga crijeva, mehanizme njihove regulacije te povezanost regulatornih polimorfizama gena COX-1 i COX-2 sa sklonošću obolijevanju i ekspresijom mRNA i proteina. Naši rezultati su pokazali da COX-1 ima zaštitnu, a COX-2 tumorigenu ulogu u sluznici debelog crijeva. Gubitak COX-1 učestali je događaj u karcinogenezi, dok COX-2 pokazuje veću varijaciju između uzoraka. Porast COX-2 ekspresije povezan je s lošijim preživljenjem oboljelih. Dokazali smo povezanost regulatornih polimorfizama sa sklonošću obolijevanju i ekspresijom gena COX-2. Ekspresija proteina odgovara mRNA ekspresiji te nema povezanosti s ekspresijom miR-200 što pokazuje da je ekspresija gena COX-1 i COX-2 primarno regulirana na razini transkripcije. Cyclooxygenases are the key enzymes in prostanoid biosynthesis. Two isoforms exist: COX-1, associated with maintainance of physiological conditions in colon; and inducible COX-2 that is mainly related to various pathologies including colorectal cancer. The aim of our study was to examine the role of COX isoforms in development and progression of sporadic colorectal cancer, mechanisms of their regulation and whether regulatory polymorphisms in COX genes are related to cancer susceptibility, mRNA and protein expression. Our results show that COX-1 has protective, and COX-2 tumorigenic role in colorectal mucosa. Loss of COX-1 is very frequent in carcinogenesis, while COX-2 shows greater variation between samples. Higher COX-2 expression correlates to worse patient survival. We proved the role of regulatory polymorphisms in cancer susceptibility, and COX-2 expression. Protein expression correlates with mRNA expression, and there is no associtation with miR-200, which indicates transcriptional regulation as the key regulatory mechanism of COX expression.

Oko 15% sporadičnih karcinoma debelog crijeva nastaje mutatorskim putem karcinogeneze kojeg karakterizira nestabilnost mikrosatelitne DNA (MSI) uzrokovana promjenama u genima iz sustava popravka krivo sparenih baza (MMR). Ovi tumori imaju različite molekularne i kliničko-patološke karakteristike, te odgovor na terapiju u odnosu na tumore s intaktnim sustavom MMR. U ovom radu analiziran je gubitak heterozigotnosti (LOH) gena hMSH2, ključnog gena sustava MMR, te učestalost nestabilnosti mikrosatelitne DNA na uzorku od 100 oboljelih od sporadičnog karcinoma debelog crijeva te su rezultati korelirani s kliničko-patološkim karakteristikama. U ispitivanju statusa LOH i MSI korištena je analiza biljega VNTR D2S123 i D2S378 odnosno fragmentarna analiza 5 biljega panela Bethesda. Informativnim se pokazalo 85 uzoraka, LOH je bio prisutan u 9.4%, a visoka MSI u 8.2% analiziranih tumora. Nije bilo statistički značajne korelacije između učestalosti LOH/MSI i kliničko-patoloških značajki oboljelih, iako je LOH/MSI bio češći u većim, slabije diferenciranim i uznapredovalim tumorima. Approximately 15% of sporadic colorectal carcinomas (CRC) arise from mutator carcinogenic pathway which is characterized by microsatellite instability (MSI) caused by deficient mismatch repair system (MMR), secondary to defects in one of MMR genes. These tumors have distinct molecular and clinical-pathological features and different response to therapy. In this study we have examined the loss of heterozygosity (LOH) at the hMSH2 gene, a crucial gene in MMR system, by VNTR (D2S123 and D2S378) analysis and microsatellite instability (MSI) using the Bethesda panel of 5 microsatellite markers in 100 CRC patients. Results were compaired with clinico-pathological characteristics of patients and their tumors. LOH was detected in 9.4% and high MSI in 8.2% analysed tumors. There was no statictically significant correlation between the LOH/MSI and clinico-pathological characteristics, although LOH/MSI was more frequent in larger, poorly differentiated and advanced stage tumors.