Drug Insight: panitumumab, a human EGFR-targeted monoclonal antibody with promising clinical activity in colorectal cancer

Inhalable pH-responsive DNA tetrahedron nanoplatform for boosting anti-tumor immune responses against metastatic lung cancer

Despite advancements in the treatment of pulmonary cancer, the existence of mucosal barriers in lung still hampered the penetration and diffusion of therapeutic agents and greatly limited the therapeutic benefits. In this work, we reported a novel inhalable pH-responsive tetrahedral DNA nanomachines with simultaneous delivery of immunomodulatory CpG oligonucleotide and PD-L1-targeting antagonistic DNA aptamer (CP@TDN) for efficient treatment of pulmonary metastatic cancer. By precisely controlling the ratios of CpG and PD-L1 aptamer, the obtained CP@TDN could specifically release PD-L1 aptamer to block PD-1/PD-L1 immune checkpoint axis in acidic tumor microenvironment, followed by endocytosis by antigen-presenting cells to generate anti-tumor immune activation and secretion of anti-tumor cytokines. Moreover, inhalation delivery of CP@TDN showed highly-efficient lung deposition with greatly enhanced intratumoral accumulation, ascribing to the DNA tetrahedron-mediated penetration of pulmonary mucosa. Resultantly, CP@TDN could significantly inhibit the growth of metastatic orthotopic lung tumors via the induction of robust antitumor responses. Therefore, our work presents an attractive approach by virtue of biocompatible DNA tetrahedron as the inhalation delivery system for effective treatment of metastatic lung cancer.

Downregulated miRNA-491-3p accelerates colorectal cancer growth by increasing uMtCK expression

Colorectal carcinoma (CRC) is the second most frequent cancer worldwide. MiR-491-3p, a tumor-suppressive microRNA (miRNA, miR), has been revealed to be abnormally expressed in CRC tissues. Meanwhile, up-regulated ubiquitous mitochondrial creatine kinase (uMtCK) contributes to CRC cell proliferation. Here we aim to explore whether aberrant miR-491-3p expression promotes CRC progression through regulating uMtCK. To this end, miR-491-3p and uMtCK levels were assessed in CRC tissues using quantitative real-time PCR (qRT-PCR). The biological roles of miR-491-3p and uMtCK in regulating CRC growth were evaluated using colony formation assay and mouse Xenograft tumour model. We found that miR-491-3p expression was decreased in CRC tissues compared with matched para-cancerous tissues, whereas uMtCK expression was increased. Functionally, miR-491-3p overexpression repressed SW480 cell growth, whereas miR-491-3p depletion accelerated SW620 cell proliferation and growth. Inversely, uMtCK positively regulated CRC cell proliferation. Mechanistically, miR-491-3p post-transcriptionally downregulated uMtCK expression by binding to 3'-UTR of uMtCK. Consequently, restoring uMtCK expression markedly eliminated the role of miR-491-3p in suppressing CRC growth. Collectively, miR-491-3p functions as a tumour suppressor gene by repressing uMtCK, and may be a potential target for CRC treatment.

CD95L cell surface cleavage triggers a prometastatic signaling pathway in triple-negative breast cancer

Triple-negative breast cancers (TNBC) lacking estrogen and progesterone receptors and HER2 amplification have a relatively high risk of metastatic dissemination, but the mechanistic basis for this risk is not understood. Here, we report that serum levels of CD95 ligand (CD95L) are higher in patients with TNBC than in other patients with breast cancer. Metalloprotease-mediated cleavage of CD95L expressed by endothelial cells surrounding tumors generates a gradient that promotes cell motility due to the formation of an unconventional CD95-containing receptosome called the motility-inducing signaling complex. The formation of this complex was instrumental for Nox3-driven reactive oxygen species generation. Mechanistic investigations revealed a Yes-Orai1-EGFR-PI3K pathway that triggered migration of TNBC cells exposed to CD95L. Our findings establish a prometastatic function for metalloprotease-cleaved CD95L in TNBCs, revisiting its role in carcinogenesis.

Imaging EGFR and HER2 by PET and SPECT: a review

In an effort to discover a noninvasive method for predicting which cancer patients will benefit from therapy targeting the EGFR and HER2 proteins, a large body of the research has been conducted toward the development of PET and SPECT imaging agents, which selectively target these receptors. We provide a general overview of the advances made toward imaging EGFR and HER2, detailing the investigation of PET and SPECT imaging agents ranging in size from small molecules to monoclonal antibodies.

Low glucose promotes CD133mAb-elicited cell death via inhibition of autophagy in hepatocarcinoma cells

CD133 on cancer stem cells is a potential therapeutic target. In this study, CD133 antibody (CD133mAb) treatment resulted in cell death in hepatoma LM3, HepG2, Hep3B and Huh-7 cells, especially under low glucose condition. The treatment also inhibited formation of spheroids, colonies, and xenograft tumors. Ectopic CD133 enabled hepatocyte L02 to be suppressed by CD133mAb and increased spheroid formation. CD133mAb caused cell death in primary HCC cells and sensitized them to Doxorubicin and Cisplatin. The antibody effect was attributed to suppressing autophagy and promoting necrotic cell death. Therefore, targeting CD133 under low glucose condition is a potential therapeutic approach for hepatocarcinomas.

Mechanistic insights into the activation of oncogenic forms of EGF receptor

Epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that is commonly activated by mutation in non-small cell lung cancer. The mechanism of this oncogenic activation is not completely understood, but in contrast to that of the wild-type EGFR, it is proposed to be independent of kinase domain dimerization. Mechanistic studies on EGFR have mainly relied on cell-based assays or isolated kinase domain measurements. Here we show, using purified, near full-length human EGFR proteins (tEGFRs), that two oncogenic mutants are fully active independently of EGF and highly resistant to the therapeutic and endogenous inhibitors cetuximab, lapatinib and MIG6. Based on the pattern of inhibition and the effects of additional asymmetric kinase dimer interface mutations, we propose that these oncogenic EGFR mutants drive and strongly depend on the formation of the asymmetric kinase dimer for activation, which has implications for drug design and cancer treatment strategies.

Preparation of cystamine core dendrimer and antibody-dendrimer conjugates for MRI angiography

Herein we report the preparation along with the in vivo and in vitro MRI characterization of two generation four and five cystamine core dendrimers loaded with thirty and fifty-eight derivatized Gd-DOTA (G4SS30, G5SS58) respectively. Likewise the development and characterization of two half-dendrimers conjugated to the F(ab')(2) fragment of the monoclonal antibody (mAb) panitumumab functionalized with a maleimide conjugation functional group site (Ab-(G4S15)(4), Ab-(G5S29)(4)) are also described. The in vitro molar relaxivity of the Ab-(G4S15)(4) conjugate, measured at pH 7.4, 22 °C, and 3T showed a moderate increase in relaxivity as compared to Magnevist (6.7 vs 4.0 mM(-1) s(-1)) while the Ab-(G5S29)(4) conjugate was 2-fold higher (9.1 vs 4.0 mM(-1) s(-1)). The data showed that only a high injection dose (0.050 mmol Gd(3+)/kg) produced a detectable contrast enhanced contrast for the Ab-(G4S15)(4) conjugate while a lower dose (0.035 mmol Gd(3+)/kg) was sufficient for the Ab-(G5S29)(4) conjugate. The antibody-SMCC conjugate was purified by a Sephadex G-100 column, and the antibody-dendrimer-based agents were purified by spin filtration using a Centricon filter (50,000 MCO). The protein assay coupled with cysteine and Ellman's assay indicated an antibody to dendrimer ratio of 1:4. The in vivo blood clearance half-lives of the four agents measured at the jugular vein were ~12-22 min.

Multidrug-resistance proteins are weak tumor associated antigens for colorectal carcinoma

BACKGROUND

Multidrug resistance (MDR) is a clinically, highly relevant phenomenon. Under chemotherapy many tumors show an increasing resistance towards the applied substance(s) and to a certain extent also towards other agents. An important molecular cause of this phenomenon is an increased expression of transporter proteins. The functional relationship between high expression levels and chemotherapy resistance makes these MDR and MRP (MDR related protein) proteins to interesting therapeutic targets. We here wanted to systematically analyze, whether these proteins are tumor specific antigens which could be targeted immunologically.

RESULTS

Using the reverse immunology approach, 30 HLA-A2.1 restricted MDR and MRP derived peptides (MDP) were selected. Stimulated T cell lines grew well and mainly contained activated CD8+ cells. Peptide specificity and HLA-A2.1 restriction were proven in IFN-γ-ELISpot analyses and in cytotoxicity tests against MDP loaded target cells for a total of twelve peptides derived from MDR-1, MDR-3, MRP-1, MRP-2, MRP-3 and MRP-5. Of note, two of these epitopes are shared between MDR-1 and MDR-3 as well as MRP-2 and MRP-3. However, comparably weak cytotoxic activities were additionally observed against HLA-A2.1+ tumor cells even after upregulation of MDR protein expression by in vitro chemotherapy.

CONCLUSIONS

Taken together, these data demonstrate that human T cells can be sensitised towards MDPs and hence, there is no absolute immunological tolerance. However, our data also hint towards rather low endogenous tumor cell processing and presentation of MDPs in the context of HLA-A2.1 molecules. Consequently, we conclude that MDR and MRP proteins must be considered as weak tumor specific antigens-at least for colorectal carcinoma. Their direct contribution to therapy-failure implies however, that it is worth to further pursue this approach.

Preparation, biological evaluation, and pharmacokinetics of the human anti-HER1 monoclonal antibody panitumumab labeled with 86Y for quantitative PET of carcinoma

Panitumumab, a human monoclonal antibody that binds to the epidermal growth factor receptor (HER1), was approved by the Food and Drug Administration in 2006 for the treatment of patients with HER1-expressing carcinoma. In this article, we describe the preclinical development of (86)Y-CHX-A''-diethylenetriaminepentaacetic acid (DTPA)-panitumumab for quantitative PET of HER1-expressing carcinoma. Panitumumab was conjugated to CHX-A''-DTPA and radiolabeled with (86)Y. In vivo biodistribution, PET, blood clearance, area under the curve, area under the moment curve, and mean residence time were determined for mice bearing HER1-expressing human colorectal (LS-174T), prostate (PC-3), and epidermoid (A431) tumor xenografts. Receptor specificity was demonstrated by coinjection of 0.1 mg of panitumumab with the radioimmunoconjugate.

RESULTS

(86)Y-CHX-A''-DTPA-panitumumab was routinely prepared with a specific activity exceeding 2 GBq/mg. Biodistribution and PET studies demonstrated a high HER1-specific tumor uptake of the radioimmunoconjugate. In mice bearing LS-174T, PC-3, or A431 tumors, the tumor uptake at 3 d was 34.6 +/- 5.9, 22.1 +/- 1.9, and 22.7 +/- 1.7 percentage injected dose per gram (%ID/g), respectively. The corresponding tumor uptake in mice coinjected with 0.1 mg of panitumumab was 9.3 +/- 1.5, 8.8 +/- 0.9, and 10.0 +/- 1.3 %ID/g, respectively, at the same time point, demonstrating specific blockage of the receptor. Normal organ and tumor uptake quantified by PET was closely related (r(2) = 0.95) to values determined by biodistribution studies. The LS-174T tumor had the highest area under the curve (96.8 +/- 5.6 %ID d g(-1)) and area under the moment curve (262.5 +/- 14.9 %ID d(2) g(-1)); however, the tumor mean residence times were identical for all 3 tumors (2.7-2.8 d).

CONCLUSION

This study demonstrates the potential of (86)Y-CHX-A''-DTPA-panitumumab for quantitative noninvasive PET of HER1-expressing tumors and represents the first step toward clinical translation.

Infectious complications associated with monoclonal antibodies and related small molecules

Biologics are increasingly becoming part of routine disease management. As more agents are developed, the challenge of keeping track of indications and side effects is growing. While biologics represent a milestone in targeted and specific therapy, they are not without drawbacks, and the judicious use of these "magic bullets" is essential if their full potential is to be realized. Infectious complications in particular are not an uncommon side effect of therapy, whether as a direct consequence of the agent or because of the underlying disease process. With this in mind, we have reviewed and summarized the risks of infection and the infectious disease-related complications for all FDA-approved monoclonal antibodies and some related small molecules, and we discuss the probable mechanisms involved in immunosuppression as well as recommendations for prophylaxis and treatment of specific disease entities.