Targeting cancer with a bi-functional peptide: in vitro and in vivo results.

BACKGROUND: Current therapies to treat cancer, although successful for some patients, have significant side-effects and a high number of patients have disease that is either non-responsive or which develops resistance. Our goal was to design a small peptide that possesses similar functions to an antibody drug conjugate with regard to targeting and killing cancer cells, but that overcomes size restrictions. MATERIALS AND METHODS: We designed a novel cancer-specific killer peptide created by fusion of the toxic peptide (KLAKLAK)2 with the cancer recognition peptide LTVSPWY. RESULTS: This bi-functional peptide showed toxicity to breast cancer, prostate cancer, and neuroblastoma cell lines. Only low toxicity to non-cancer cells, colon cancer, lung cancer, and lymphoma cell lines was observed. In vivo injections of the bi-functional peptide caused tumor growth retardation compared to mice treated with control peptides. The bi-functional peptide caused retardation of MDA-MB-435S tumors in vivo and increased survival to 80% at day 100 after tumor implantation, whereas all control animals died at day 70. Previous reports showed that the recognition moiety LTVSPWY targets the tumor-associated antigen HER2. Here we found that our new peptide TP-Tox also excerts toxic effects on HER2-negative cell lines. Therefore, we searched for the molecular target of the bi-specific peptide using immunoprecipitation and mass spectrometry. Our data suggest a possible interaction with RAS GTPase-activating protein binding protein 1 (G3BP1). CONCLUSION: We designed a bi-functional peptide of 23 amino acids and demonstrated its ability to bind and kill several cancer cell lines in vitro and to strongly increase survival in breast cancer bearing mice in vivo. This novel toxin could be used in future cancer therapies and warrants further pre-clinical and clinical exploration.

Membrane protein interactions between different Arabidopsis thaliana MRS2-type magnesium transporters are highly permissive.

Membrane proteins of the Arabidopsis thaliana MRS2 (MGT) family have been characterised as magnesium transporters. Like their bacterial CorA homologues, the plant MRS2 proteins are characterised by an invariable GMN tripeptide motif terminating the first of two closely spaced transmembrane domains at the carboxy-termini. The functional Mg(2+) transport channel is assembled as a pentamer in the case of CorA. However, in contrast to the single CorA genes of bacteria, plant genomes encode up to 10 highly divergent MRS2 proteins. To elucidate structure-function relationships and the possibility of plant MRS2 hetero-pentamer formation, we performed protein-protein interaction studies in the yeast mating-based split-ubiquitin system (mbSUS) and concomitant protein modelling using I-TASSER. Despite very restricted sequence similarities and variable polypeptide insertions all AtMRS2 proteins feature the key structural elements determined for the CorA crystal structure. The mbSUS setup conclusively demonstrates protein-protein interactions of any given AtMRS2 protein not only with itself but also highly permissive interactions to varying degrees among all AtMRS2 proteins. AtMRS2-3 seems particularly prone to non-selective, strong interactions with the other homologues. Deletion constructs show that six amino acids may be deleted from the carboxy-terminus and 27 (but not 41) from the amino-terminus of AtMRS2-7 without impairment of homologous or heterologous protein interactions. Despite significant diversification, the plant MRS2 proteins have obviously retained an ancient CorA/MRS2 core structure and the capacity for protein-protein interactions. Plant magnesium homeostasis may be influenced by hetero-oligomer channel formation where different plant MRS2 proteins meet in the same membrane naturally or in transgenic approaches.

Efficacy of a proapoptotic peptide towards cancer cells.

BACKGROUND: Conventional cancer therapies are associated with severe side-effects and the development of drug resistance. Therefore, new strategies to specifically target tumor cells leaving healthy tissue unaffected are of great interest. MATERIALS AND METHODS: On this respect, we tested the antimicrobial peptide (KLAKLAK)(2). RESULTS: This peptide exhibits cytotoxicity against human breast cancer and other tumor cells, while healthy cells remain unaffected. Moreover, treatment with this cationic amphipathic peptide results in slower tumor growth and longer overall survival in vivo. CONCLUSION: Our data suggest a potential use of (KLAKLAK)(2) peptide for patients with breast and other types of cancer.

Influencing the Wnt signaling pathway in multiple myeloma.

Recent studies have implicated genetic and epigenetic aberrations resulting in aberrant activation of the Wingless-Int (Wnt) pathway and thus influencing the initiation and progression of multiple myeloma (MM). Of major importance, these findings may lead to novel treatment strategies exploiting targeted modulation of Wnt signaling. This review describes the current status of knowledge concerning the role of Wnt pathway alteration in MM and outlines future lines of research and their clinical perspectives.

A root-expressed magnesium transporter of the MRS2/MGT gene family in Arabidopsis thaliana allows for growth in low-Mg2+ environments.

The MRS2/MGT gene family in Arabidopsis thaliana belongs to the superfamily of CorA-MRS2-ALR-type membrane proteins. Proteins of this type are characterized by a GMN tripeptide motif (Gly-Met-Asn) at the end of the first of two C-terminal transmembrane domains and have been characterized as magnesium transporters. Using the recently established mag-fura-2 system allowing direct measurement of Mg(2+) uptake into mitochondria of Saccharomyces cerevisiae, we find that all members of the Arabidopsis family complement the corresponding yeast mrs2 mutant. Highly different patterns of tissue-specific expression were observed for the MRS2/MGT family members in planta. Six of them are expressed in root tissues, indicating a possible involvement in plant magnesium supply and distribution after uptake from the soil substrate. Homozygous T-DNA insertion knockout lines were obtained for four members of the MRS2/MGT gene family. A strong, magnesium-dependent phenotype of growth retardation was found for mrs2-7 when Mg(2+) concentrations were lowered to 50 microM in hydroponic cultures. Ectopic overexpression of MRS2-7 from the cauliflower mosaic virus 35S promoter results in complementation and increased biomass accumulation. Green fluorescent protein reporter gene fusions indicate a location of MRS2-7 in the endomembrane system. Hence, contrary to what is frequently found in analyses of plant gene families, a single gene family member knockout results in a strong, environmentally dependent phenotype.