ALR (MLL2) is a member of the human MLL family, which belongs to a larger SET1 family of histone methyltransferases. We found that ALR is present within a stable multiprotein complex containing a cohort of proteins shared with other SET1 family complexes and several unique components, such as PTIP and the jumonji family member UTX. Like other complexes formed by SET1 family members, the ALR complex exhibited strong H3K4 methyltransferase activity, conferred by the ALR SET domain. By generating ALR knockdown cell lines and comparing their expression profiles to that of control cells, we identified a set of genes whose expression is activated by ALR. Some of these genes were identified by chromatin immunoprecipitation as direct ALR targets. The ALR complex was found to associate in an ALR-dependent fashion with promoters and transcription initiation sites of target genes and to induce H3K4 trimethylation. The most characteristic features of the ALR knockdown cells were changes in the dynamics and mode of cell spreading/polarization, reduced migration capacity, impaired anchorage-dependent and -independent growth, and decreased tumorigenicity in mice. Taken together, our results suggest that ALR is a transcriptional activator that induces the transcription of target genes by covalent histone modification. ALR appears to be involved in the regulation of adhesion-related cytoskeletal events, which might affect cell growth and survival.

DAP kinase is a new type of calcium/calmodulin-dependent enzyme that phosphorylates serine/threonine residues on proteins. Its structure contains ankyrin repeats and the 'death' domain, and it is associated with the cell cytoskeleton. The gene encoding DAP kinase was initially isolated as a positive mediator of apoptosis induced by interferon-gamma, by using a strategy of functional cloning. We have now tested whether this gene has tumour-suppressive activity. We found that lung carcinoma clones, characterized by their highly aggressive metastatic behaviour and originating from two independent murine lung tumours, did not express DAP kinase, in contrast to their low-metastatic counterparts. Restoration of DAP kinase to physiological levels in high-metastatic Lewis carcinoma cells suppressed their ability to form lung metastases after intravenous injection into syngeneic mice, and delayed local tumour growth in a foreign 'microenvironment' Conversely, in vivo selection of rare lung lesions following injection into syngeneic mice of low-metastatic Lewis carcinoma cells or of DAP kinase transfectants, was associated with loss of DAP kinase expression. In situ TUNEL staining of tumour sections revealed that DAP kinase expression from the transgene raised the incidence of apoptosis in vivo. DAP-kinase transfectants also showed increased sensitivity in vitro to apoptotic stimuli, of the sort encountered by metastasizing cells at different stages of malignancy. We propose that loss of DAP kinase expression provides a unique mechanism that links suppression of apoptosis to metastasis.

Highlights d Novel mouse system to uncouple tumor mutational load and tumor heterogeneity d Lower tumor heterogeneity leads to decreased tumor growth because of immune rejection d Both clone numbers and their genetic diversity mediate tumor growth and rejection d Tumor heterogeneity is linked to patient survival and checkpoint blockade response

NK cells are able to kill virus-infected and tumor cells via a panel of lysis receptors. Cells expressing class I MHC proteins are protected from lysis primarily due to the interactions of several families of NK receptors with both classical and nonclassical class I MHC proteins. In this study we show that a class I MHC-deficient melanoma cell line (1106mel) is stained with several Ig-fused lysis receptors, suggesting the expression of the appropriate lysis ligands. Surprisingly, however, this melanoma line was not killed by CD16-negative NK clones. The lack of killing is shown to be the result of homotypic CD66a interactions between the melanoma line and the NK cells. Furthermore, 721.221 cells expressing the CD66a protein were protected from lysis by YTS cells and by NK cells expressing the CD66a protein. Redirected lysis experiments demonstrated that the strength of the inhibitory effect is correlated with the levels of CD66a expression. Finally, the expression of CD66a protein was observed on NK cells derived from patients with malignant melanoma. These findings suggest the existence of a novel class I MHC-independent inhibitory mechanism of human NK cell cytotoxicity. This may be a mechanism that is used by some of the class I MHC-negative melanoma cells to evade attack by CD66a-positive NK cells.

The high toxicity of most chemotherapeutic drugs and their inactivation by multidrug resistance phenotypes motivated extensive search for drugs with new modes of action. We designed a short cationic diastereomeric peptide composed of D-and L-leucines, lysines, and arginines that has selective toxicity toward cancer cells and significantly inhibits lung metastasis formation in mice (86%) with no detectable side effects. Its ability to depolarize the transmembrane potential of cancer cells at the same rate (within minutes) and concentration (3 M), at which it shows biological activity, suggests a killing mechanism that involves plasma membrane perturbation. Confocal microscopy experiments verified that the cells died as a result of acute injury, swelling, and bursting, suggesting necrosis. Biosensor binding experiments and attenuated total reflectance-Fourier transform infrared spectroscopy using model membranes have substantiated its high selectivity toward cancer cells. Although this is an initial study that looked at tumor formation rather than the ability of the peptides to reduce established tumors, the simple sequence of the peptide, its high solubility, substantial resistance to degradation, and inactivation by serum components might make it a good candidate for future anticancer treatment.Current anticancer chemotherapies that are based on alkylating agents, antimetabolites, and natural products respond incompletely; this is probably related to the development of drug resistance. Most chemotherapeutic agents also affect normal cells and consequently cause severe side effects (1). Thus, there is an urgent need to develop new classes of anticancer drugs with new modes of action that selectively target the cancer cells. A promising group under investigation includes cationic antimicrobial peptides, which are known to play an important role in the innate immunity of a diverse range of organisms, including insects, amphibians, and mammals (2). Most of these peptides have an amphipathic structure, and they preferentially bind and insert into negatively charged cell membranes. Consequently, destabilization of the membrane disturbs the electrolyte balance and induces the intracellular contents to leak, leading to cell death. In contrast to normal eukaryotic cells, which generally have low membrane potentials and whose outer leaflet almost exclusively consists of zwitterionic phospholipids, the prokaryotic and cancer cell membranes maintain large transmembrane potentials and have a higher content of anionic phospholipids on their outer leaflet. Many antimicrobial peptides therefore preferentially disrupt prokaryotic and cancer cell membranes rather than eukaryotic membranes (3).Several in vitro studies were conducted with native all L-amino acid antimicrobial peptides with defined ␣-helical or ␤-sheet secondary structures (3). However, the use of native antimicrobial peptides in vivo is mainly limited due to the loss of their function in serum, partially because of enzymatic degradation and binding to serum compone...