Photodynamic therapy (PDT) is a valuable treatment method for vulvar intraepithelial neoplasia (VIN). It allows for the treatment of a multifocal disease with minimal tissue destruction. 5-Aminolevulinic acid (5-ALA) is the most commonly used prodrug, which is converted in the heme pathway to protoporphyrin IX (PpIX), an actual photosensitizer (PS). Unfortunately, not all patients treated with PDT undergo complete remission. The main cause of their failure is resistance to anticancer therapy. In many cancers, resistance to various anticancer treatments is correlated with increased activity of the DNA repair protein apurinic/apyrimidinic endonuclease 1 (APE1). Enhanced activity of drug pumps may also affect the effectiveness of therapy. To investigate whether multidrug resistance mechanisms underlie PDT resistance in VIN, porphyrins were isolated from sensitive and resistant vulvar cancer cells and their culture media. APE1 activity was measured, and survival assay after PDT combined with APE1 inhibitor was performed. Our results revealed that resistant cells accumulated and effluxed less porphyrins than sensitive cells, and in response to PDT, resistant cells increased APE1 activity. Moreover, PDT combined with inhibition of APE1 significantly decreased the survival of PDT-resistant cells. This means that resistance to PDT in vulvar cancer may be the result of alterations in the heme synthesis pathway. Moreover, increased APE1 activity may be essential for the repair of PDT-mediated DNA damage, and inhibition of APE1 activity may increase the efficacy of PDT.

Cellular functions are largely performed by proteins. Defects in the production, folding, or removal of proteins from the cell lead to perturbations in cellular functions that can result in pathological conditions for the organism. In cells, molecular chaperones are part of a network of surveillance mechanisms that maintains a functional proteome. Chaperones are involved in the folding of newly synthesized polypeptides and assist in refolding misfolded proteins and guiding proteins for degradation. The present review focuses on the molecular co-chaperone prefoldin. Its canonical function in eukaryotes involves the transfer of newly synthesized polypeptides of cytoskeletal proteins to the tailless complex polypeptide 1 ring complex (TRiC/CCT) chaperonin which assists folding of the polypeptide chain in an energy-dependent manner. The canonical function of prefoldin is well established, but recent research suggests its broader function in the maintenance of protein homeostasis under physiological and pathological conditions. Interestingly, non-canonical functions were identified for the prefoldin complex and also for its individual subunits. We discuss the latest findings on the prefoldin complex and its subunits in the regulation of transcription and proteasome-dependent protein degradation and its role in neurological diseases, cancer, viral infections and rare anomalies.

No abstract

Translation is a core process of cellular protein homeostasis and, thus, needs to be tightly regulated. The production of newly synthesized proteins adapts to the current needs of the cell, including the response to conditions of oxidative stress. Overall protein synthesis decreases upon oxidative stress. However, the selective production of proteins is initiated to help neutralize stress conditions. In contrast to higher eukaryotes, fungi require three translation elongation factors, eEF1, eEF2, and eEF3, for protein synthesis. eEF1 and eEF2 are evolutionarily conserved, but they alone are insufficient for the translation elongation process. eEF3 is encoded by two paralogous genes, YEF3 and HEF3. However, only YEF3 is essential in yeast, whereas the function of HEF3 remains unknown. To elucidate the cellular function of Hef3p, we used cells that were depleted of HEF3 and treated with H2O2 and analyzed the growth of yeast, global protein production, and protein levels. We found that HEF3 is necessary to withstand oxidative stress conditions, suggesting that Hef3p is involved in the selective production of proteins that are necessary for defense against reactive oxygen species.

No abstract

No abstract

Glioblastoma is the most aggressive primary brain tumor. Treatment regimens for glioblastoma tumors, such as surgery, radiotherapy, and chemotherapy, are very invasive and can only prolong the median patient life to several months. It was shown that 5-aminolevulinic acid (5-ALA)-based photodynamic therapy (PDT) is a promising and less aggressive adjuvant modality for diagnosis and treatment of glioblastoma. Limiting point of PDT outcome is appearing of cells with intrinsic or acquired PDT resistance that finally results in repopulating the tumor and short-term survival of glioma patients. Therefore, our study was designed to determine therapy resistance markers in PDT resistant glioblastoma cell line. Potential markers subsequently can be used for sensitization of glioblastoma to PDT. Glioblastoma (U-87) cell line resistant to PDT (U-87R) was isolated from parental, sensitive line (U-87P) by applying several cycles of ALA-PDT, and further growing of surviving cells. U-87R cells subsequently were characterized from different aspects such as epigenetic markers, cell cycle events, oxidative stress and DNA repair capacity. Assessment of nucleotide modifications and epigenetic marks in PDT resistant glioblastoma and its parental cell line showed significant higher level of two epigenetic marks including 5-methylcytosine (5-mC) and 5-hydroxymethylcytosine (5-hmC) in U-87R compare to U-87P, before and after PDT. Doubling time of U-87R cells was considerably longer than that of U-87P. Cell cycle analysis showed longer G1 phase in U-87R cells compare to U-87P. Moreover, accumulation in G2 phase following PDT was observed earlier in resistant cells than in parental line. That suggests the role of early activation of DNA damage response in resistant cells. Resistant glioblastoma cells were then sensitized to PDT by applying inhibitor of one of the main kinases of DNA damage response, ATM kinase. In comparison with parental cells, U-87R cells also showed higher activity of some DNA base excision repair (BER) enzymes including glycosylases and AP-endonuclease1 (APE1). Studies of the whole protein profile of PDT resistant and parental cells demonstrated that the level of superoxide dismutase (SOD) was considerably higher in U-87R than in U-87P. That data was then confirmed by detecting lower oxidative stress in U-87R following PDT. PDT resistant glioblastoma cells as a model of resistant cells in glioblastoma tumor population demonstrated the significant role of epigenetic mark profile, cell cycle alteration, higher DNA repair capacity, and antioxidant defense in conferring resistance to photodynamic therapy. This work was supported by the Polish National Science Centre (NCN) grants: DEC-2012/07/B/NZ1/00008, UMO-2014/15/B/NZ5/01444, UMO-2014/13/N/NZ3/00863 Note: This abstract was not presented at the meeting. Citation Format: Somayeh Shahmoradi Ghahe, Karolina Kopania, Agata Ciuba, Marek Foksinski, Ryszard Oliński, Barbara Tudek. The role of epigenetic mark profile, cell cycle alteration and DNA repair in resistance of glioblastoma cells to photodynamic therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2049. doi:10.1158/1538-7445.AM2017-2049

No abstract