Aldehyde dehydrogenase 1A1 and 1A3 isoforms - mechanism of activation and regulation in cancer.

In some types of human cancer, aldehyde dehydrogenases represent stemness markers and their expression is associated with advanced disease stages and poor prognosis. Although several biological functions are mediated by their product Retinoid acid, the molecular mechanism is tissue-dependent and only partially understood. In this review, we summarize the current knowledge about the role of ALDH in solid tumours, especially ALDH1A1 and ALDH1A3 isoforms, regarding the molecular mechanism of their transcription and regulation, and their crosstalk with main molecular pathways resulting in the excessive proliferation, chemoresistance, stem cells properties and invasiveness. The recent knowledge of the regulatory effect of lnRNA on ALDH1A1 and ALDH1A3 is discussed too.

Assessing the effect of RET transmembrane domain mutations in receptor self-association capability using the in vivo TOXCAT system.

Mutations of c-RET proto-oncogene with a unique localization within the human transmembrane receptor represent a challenge for contemporary molecular oncology techniques. RET transmembrane domain (TMD)-driven dimerization of the receptor leads to its permanent activation that eventually results in the development of medullary thyroid neoplasia. In this study, we describe the employment of the TOXCAT system which enables to investigate mutation-induced alterations in the strength of RET TMD dimerization in vivo. We suggest an improvement of the method by adding reporter gene quantification at the mRNA levels as a support to the commonly used reporter protein level. We have investigated possible changes in RET TMD dimerization in case of two germline RET TMD mutations found in in several individual cases and MEN2 families worldwide, p.Ala641Ser and p.Ser649Leu. According to our results, substitution of Ser-649 residue by leucine, found as a result of germline mutation, caused a significant decrease of RET TMD self-association in comparison to RET wild-type transmembrane domain. The impaired ability of self-association suggests a novel, yet unknown mechanism of tyrosine kinase domain activation, possibly independent of RET homodimerization.

Novel germline mutation in the transmembrane region of RET gene close to Cys634Ser mutation associated with MEN 2A syndrome.

Two mutations on the same allele of RET gene were revealed in a family with predisposition to multiple endocrine neoplasia (MEN) type 2A. The first mutation changes codon 634 from cysteine to serine. The second, a novel mutation in codon 641, changes alanine to serine in the transmembrane domain of the RET protein. Two mutations were present in close proximity in both the patients' germline and tumor DNA and were absent in DNA isolated from healthy family members and control blood donors. All MEN 2A affected family members suffered from medullary thyroid carcinoma and two of ten patients for pheochromocytoma. No parathyroid gland alterations were observed in patients with two RET gene mutations. Analysis of four genetic polymorphisms in the RET gene showed higher incidence of polymorphisms of exons 11 and 15. The observed allelic imbalance in favor of mutated allele in pheochromocytoma corresponded to higher expression of the RET gene. These observations confirm the multifactorial process leading to development of MEN 2A syndrome.

Cytotoxicity and mode of action of the potential cytostatic drug oracin.

Primary screening in vitro and study on the mode of action of oracin in Ehrlich ascites carcinoma cells have been performed. The measure of the cytotoxic effect was the degree of inhibition of 14C-adenine and 14C-valine incorporation into TCA insoluble fraction of Ehrlich ascites carcinoma (EAC) cells. The inhibitory effect was characterized by IC50 values. The biosynthesis of nucleic acides indicated by the incorporation of 14C-adenine was more sensitive (IC50 = 66 micromol/ l) than the biosynthesis of proteins indicated by the incorporation of 14C-valine (IC50 = 196 micromol/l). To elucidate the biochemical mode of action, the effect of oracin on dynamics of biosynthesis of macromolecules indicated by the incorporation rate of [14C] labeled precursors (adenine, thymidine, uridine, valine) into appropriate macromolecules of EAC cells was studied. Oracin inhibited incorporation of all four precursors into the trichloracetic acid - insoluble fraction of Ehrlich ascites cells. The extent of inhibition was dependent on both time and drug concentration. We found that oracin inhibited activity of topoisomerase II by 100% at concentration 5 to 15 micromol/l.

Germline mutation of the RET proto-oncogene in members of Slovak families with multiple endocrine neoplasia 2.

Detection of mutations in RET proto-oncogene in Slovak families from different localities and of different ethnic origin with MEN 2 syndrome is reported. Despite the fact that the same mutation of RET oncogene was found in different family members, the latency period of tumor appearance and their pathogenicity differed substantially. In addition, also different phenotypes of the disease were expressed in various family members having the same RET gene mutation. The data indicate that the mechanism of MEN2 syndrome is not only due to the RET gene mutation, and strongly support the conclusion that additional genetic events are involved in the disease formation.