Conventional cancer treatment strategies assume that maximum patient benefit is achieved through maximum killing of tumor cells. However, by eliminating the therapy-sensitive population, this strategy accelerates emergence of resistant clones that proliferate unopposed by competitors—an evolutionary phenomenon termed “competitive release.” We present an evolution-guided treatment strategy designed to maintain a stable population of chemosensitive cells that limit proliferation of resistant clones by exploiting the fitness cost of the resistant phenotype. We treated MDA-MB-231/luc triple-negative and MCF7 estrogen receptor–positive (ER+) breast cancers growing orthotopically in a mouse mammary fat pad with paclitaxel, using algorithms linked to tumor response monitored by magnetic resonance imaging. We found that initial control required more intensive therapy with regular application of drug to deflect the exponential tumor growth curve onto a plateau. Dose-skipping algorithms during this phase were less successful than variable dosing algorithms. However, once initial tumor control was achieved, it was maintained with progressively smaller drug doses. In 60 to 80% of animals, continued decline in tumor size permitted intervals as long as several weeks in which no treatment was necessary. Magnetic resonance images and histological analysis of tumors controlled by adaptive therapy demonstrated increased vascular density and less necrosis, suggesting that vascular normalization resulting from enforced stabilization of tumor volume may contribute to ongoing tumor control with lower drug doses. Our study demonstrates that an evolution-based therapeutic strategy using an available chemotherapeutic drug and conventional clinical imaging can prolong the progression-free survival in different preclinical models of breast cancer.

LL-37 is a cationic, amphipathic alpha-helical antimicrobial peptide found in humans that kills cells by disrupting the cell membrane. To disrupt membranes, antimicrobial peptides such as LL-37 must alter the hydrophobic core of the bilayer. Differential scanning calorimetry and deuterium ((2)H) NMR experiments on acyl chain perdeuterated lipids demonstrate that LL-37 inserts into the hydrophobic region of the bilayer and alters the chain packing and cooperativity. The results show that hydrophobic interactions between LL-37 and the hydrophobic acyl chains are as important for the ability of this peptide to disrupt lipid bilayers as its electrostatic interactions with the polar headgroups. The (2)H NMR data are consistent with the previously determined surface orientation of LL-37 (Henzler Wildman, K. A., et al. (2003) Biochemistry 42, 6545) with an estimated 5-6 A depth of penetration of the hydrophobic face of the amphipathic helix into the hydrophobic interior of the bilayer. LL-37 also alters the material properties of lipid bilayers, including the area per lipid, hydrophobic thickness, and coefficient of thermal expansion in a manner that varies with lipid type and temperature. Comparison of the effect of LL-37 on 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC-d(31)) and 1,2-dimyristoyl-phosphatidylcholine (DMPC-d(54)) at different temperatures demonstrates the importance of bilayer order in determining the type and extent of disordering and disruption of the hydrophobic core by LL-37. One possible explanation, which accounts for both the (2)H NMR data presented here and the known surface orientation of LL-37 under identical conditions, is that bilayer order influences the depth of insertion of LL-37 into the hydrophobic/hydrophilic interface of the bilayer, altering the balance of electrostatic and hydrophobic interactions between the peptide and the lipids.

Metastasis is a multistep process that culminates in the spread of cells from a primary tumor to a distant site or organs. For tumor cells to be able to metastasize, they have to locally invade through basement membrane into the lymphatic and the blood vasculatures. Eventually they extravasate from the blood and colonize in the secondary organ. This process involves multiple interactions between the tumor cells and their microenvironments. The microenvironment surrounding tumors has a significant impact on tumor development and progression. A key factor in the microenvironment is an acidic pH. The extracellular pH of solid tumors is more acidic in comparison to normal tissue as a consequence of high glycolysis and poor perfusion. It plays an important role in almost all steps of metastasis. The past decades have seen development of technologies to non-invasively measure intra- and/or extracellular pH. Most successful measurements are MR-based, and sensitivity and accuracy have dramatically improved. Quantitatively imaging the distribution of acidity helps us understand the role of the tumor microenvironment in cancer progression. This review discusses different MR methods in measuring tumor pH along with emphasizing the importance of extracelluar tumor low pH on different steps of metastasis; more specifically focusing on Epithelial to Mesenchymal transition (EMT), and anti cancer immunity.

Purpose A significant limitation of checkpoint blockade immunotherapy is the relatively low response rate (e.g. ~20% with PD-1 blockade in lung cancer). In this study, we tested whether strategies which increase T cell infiltration to tumors can be efficacious in enhancing immunotherapy response. Experimental Design We performed an unbiased screen to identify FDA-approved oncology agents with ability to enhance T cell chemokine expression with the goal of identifying agents capable of augmenting immunotherapy response. Identified agents were tested in multiple lung tumor models as single agents and in combination with PD-1 blockade. Additional molecular and cellular analysis of tumors was used to define underlying mechanisms. Results We found that histone deacetylase (HDAC) inhibitors (HDACi) increased expression of multiple T cell chemokines in cancer cells, macrophages and T cells. Using the HDACi romidepsin in vivo, we observed increased chemokine expression, enhanced T cell infiltration, and T cell-dependent tumor regression. Importantly, romidepsin significantly enhanced the response to PD-1 blockade immunotherapy in multiple lung tumor models, including nearly complete rejection in two models. Combined romidepsin and PD-1 blockade also significantly enhanced activation of tumor-infiltrating T cells. Conclusions These results provide evidence for a novel role of HDACs in modulating T cell chemokine expression in multiple cell types. In addition, our findings indicate that pharmacological induction of T cell chemokine expression represents a conceptually novel approach for enhancing immunotherapy response. Finally, these results suggest that combination of HDAC inhibitors with PD-1 blockade represents a promising strategy for lung cancer treatment.

Short alanine peptides, containing 16 or 17 residues, appear to form alpha-helices in aqueous solution. But the main spectroscopic analyses used on helical peptides (circular dichroism and nuclear magnetic resonance) cannot distinguish between an alpha-helix (in which the ith residue is hydrogen-bonded to residue i + 4; ref. 9) and the next most common peptide helix, the 3(10)-helix10 (i-->i + 3 hydrogen-bonding). To address this problem we have designed single and doubly spin-labelled analogues of alanine-based peptides in which the nitroxide spin label forms an unbranched side chain extending from the sulphur atom of a cysteine residue. Here we report the circular dichroism, Fourier-transform infrared and electron-spin resonance spectra of these peptides under helix-forming conditions. The infrared absorbance gives an amide I' band with a frequency that is substantially different from that observed for alpha-helices. The electron-spin resonance spectra of doubly labelled helices show that the ranking of distances between side chains, around a single turn (residues 4-8), is inconsistent with an alpha-helical structure. Our experiments suggest that the more likely peptide geometry is a 3(10)-helix.

Previous studies using MR spectroscopy have shown that the extracellular pH (pH e ) of tumors is acidic compared to normal tissues. This has a number of important sequelae that favor the emergence of more aggressive and therapy-resistant tumors. New MRI methods based on pH-sensitive T 1 relaxivity are an attractive alternative to previous spectroscopic methods, as they allow improvements in spatial and temporal resolution. Recently, pH-dependent GdDOTA-4AmP 5-and a pH-independent analog, GdDOTP 5-, were used to image renal pH in mice. The current study has used a similar approach to image pH e in rat gliomas. Significant differences were observed compared to the renal study. First, the relaxivity of GdDOTP 5-was found to be affected by the higher extracellular protein content of tumors. Second, the pixel-by-pixel analysis of the GdDOTP 5-and GdDOTA-4AmP 5-pharmacokinetics showed significant dispersion, likely due to the temporal fluctuations in tumor perfusion. However, there was a robust correlation between the maximal enhancements produced by the two boluses. Therefore, to account for the local time-courses differences, pH e maps were calculated at the time of maximal enhancement in each pixel.

In the design of lipid-coated microbubble ultrasound contrast agents for molecular imaging and targeted drug delivery, the surface distribution of the shell species is important because it dictates such properties as ligand location, brush coverage, and amount of drug loading. We used a combination of spectroscopy and microscopy techniques to test the prevailing notion that the main phosphatidyl choline (PC) and lipopolymer species are completely miscible within the monolayer shell. NMR spectroscopy showed that the shell composition is roughly equivalent to the bulk lipid ratio. FTIR spectroscopy showed a sharp melting peak corresponding to the main phase-transition temperature of the main PC species, with no observed pretransitions while scanning from room temperature, indicating a single PC-rich ordered phase. Electron and fluorescence microscopy showed a heterogeneous microstructure with dark (ordered) domains and bright (disordered) regions. Domain formation was thermotropic and reversible. Fluorescent labeling of the lipopolymer following shell formation showed that it partitions preferentially into the disordered interdomain regions. The ordered domains, therefore, are composed primarily of PC, and the disordered interdomain regions are enriched in lipopolymer. Phase heterogeneity was observed at all lipopolymer concentrations (0.5 to 20 mol %), and the degree of phase separation increased with lipopolymer content. The composition and temperature dependence of the microstructure indicates that phase separation is driven thermodynamically rather than being a kinetically trapped relic of the shell-formation process. The overall high variation in microstructure, including the existence of anomalous three-phase coexistence, highlights the nonequilibrium (history-dependent) nature of the monolayer shell.

CONSPECTUSMagnetic resonance imaging (MRI) has inherent advantages in safety, three-dimensional output, and clinical relevance when compared with optical and radiotracer imaging methods. However, MRI contrast agents are inherently less sensitive than agents used in other imaging modalities primarily because MRI agents are detected indirectly by changes in either the water proton relaxation rates (T 1 , T 2 , and T 2 *) or water proton intensities (chemical exchange saturation transfer and paramagnetic chemical exchange saturation transfer, CEST and PARACEST). Consequently, the detection limit of an MRI agent is determined by the characteristics of the background water signal; by contrast, optical and radiotracer-based methods permit direct detection of the agent itself. By virtue of responding to background water (which reflects bulk cell properties), however, MRI contrast agents have considerable advantages in "metabolic" imaging-that is, spatially resolving tissue variations NIH Public Access Author ManuscriptAcc Chem Res. Author manuscript; available in PMC 2010 July 21. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript in pH, redox state, oxygenation, or metabolite levels. In this Account, we begin by examining sensitivity limits in targeted contrast agents and then address contrast agents that respond to a physiological change; these responsive agents are effective metabolic imaging sensors.The sensitivity requirements for a metabolic imaging agent are quite different from those for a targeted Gd 3+ -based T 1 agent (for sensing cell receptors, for example). Targeted Gd 3+ agents must have either an extraordinarily high water proton relaxivity (r 1 ) or multiple Gd 3+ complexes clustered together at the target site on a polymer platform or nanoparticle assembly. Metabolic MRI agents differ in that the high relaxivity requirement, although helpful, is eased because these agents respond to bulk properties of tissues rather than low concentrations of a specific biological target. For optimal sensing, metabolic imaging agents should display a large change in relaxivity (Δr 1 ) in response to the physiological or metabolic parameter of interest.Metabolic imaging agents have only recently begun to appear in the literature and only a few have been demonstrated in vivo. MRI maps of absolute tissue pH have been obtained with Gd 3+ -based T 1 sensors. The requirement of an independent measure of agent concentration in tissues complicates these experiments, but if qualitative changes in tissue pH are acceptable, then these agents can be quite useful. Finally, we describe examples of imaging extracellular pH in brain tumors, ischemic hearts, and pancreatic islets with Gd 3+ -based pH sensors and discuss the potential of CEST and PARACEST agents as metabolic imaging sensors. IntroductionMagnetic resonance imaging is a spectacular tool for providing high resolution anatomical images of rodents and humans but is markedly less sensitive than optical or radiotracer imaging modalities for most molecu...