Lewis blood group and CEA related antigens; coexpressed cell-cell adhesion molecules with roles in the biological progression and dissemination of tumours

CircHAS2 activates CCNE2 to promote cell proliferation and sensitizes the response of colorectal cancer to anlotinib

BACKGROUND

Tyrosine kinase inhibitors (TKIs) are crucial in the targeted treatment of advanced colorectal cancer (CRC). Anlotinib, a multi-target TKI, has previously been demonstrated to offer therapeutic benefits in previous studies. Circular RNAs (circRNAs) have been implicated in CRC progression and their unique structural stability serves as promising biomarkers. The detailed molecular mechanisms and specific biomarkers related to circRNAs in the era of targeted therapies, however, remain obscure.

METHODS

The whole transcriptome RNA sequencing and function experiments were conducted to identify candidate anlotinib-regulated circRNAs, whose mechanism was confirmed by molecular biology experiments. CircHAS2 was profiled in a library of patient-derived CRC organoids (n = 22) and patient-derived CRC tumors in mice. Furthermore, a prospective phase II clinical study of 14 advanced CRC patients with anlotinib-based therapy was commenced to verify drug sensitivity (ClinicalTrials.gov identifier: NCT05262335).

RESULTS

Anlotinib inhibits tumor growth in vitro and in vivo by downregulating circHAS2. CircHAS2 modulates CCNE2 activation by acting as a sponge for miR-1244, and binding to USP10 to facilitate p53 nuclear export as well as degradation. In parallel, circHAS2 serves as a potent biomarker predictive of anlotinib sensitivity, both in patient-derived organoids and xenograft models. Moreover, the efficacy of anlotinib inclusion into the treatment regimen yields meaningful clinical responses in patients with high levels of circHAS2. Our findings offer a promising targeted strategy for approximately 52.9% of advanced CRC patients who have high circHAS2 levels.

CONCLUSIONS

CircHAS2 promotes cell proliferation via the miR-1244/CCNE2 and USP10/p53/CCNE2 bidirectional axes. Patient-derived organoids and xenograft models are employed to validate the sensitivity to anlotinib. Furthermore, our preliminary Phase II clinical study, involving advanced CRC patients treated with anlotinib, confirmed circHAS2 as a potential sensitivity marker.

Open, Laparoscopic, and Robotic Approaches to Treat Colorectal Cancer: A Comprehensive Review of Literature

Surgery is usually required to treat colorectal cancer (CRC). Medical technology has advanced, providing various approaches to tackle this disease. Different surgeries are available, such as laparoscopic surgery, single-incision laparoscopic surgery, natural orifice transluminal endoscopic surgery, and robotic surgery. Laparoscopic surgery has several benefits including reduced blood loss and shorter recovery time. It can also improve lung function and minimize complications. However, it requires more time to perform and has a higher risk of complications during the procedure. Robotic surgery provides a three-dimensional view of the surgical area allowing for greater precision in rectal surgeries and access to difficult-to-reach pelvic regions. This method utilizes robotics technology which reduces surgical time and speeds up recovery for patients. There are various surgical options available for treating CRC; however, laparoscopic surgery and robotic surgery offer unique advantages despite their own drawbacks. As technology continues to evolve, medical techniques will continue improving existing methods while providing new options resulting in better outcomes for patients. Compared to laparoscopy, robotic surgery has a lower rate of operative conversions and a shorter learning curve. However, it also has some drawbacks, such as a longer docking time, lack of tactile sensation, and higher cost. Therefore, the choice of surgical method should depend on patient characteristics, surgeon preference and expertise, and available resources. Currently, specialized centers offer robotic surgeries which are more expensive and take longer compared to open and laparoscopic approaches. Nonetheless, they are considered safe and feasible when compared to traditional surgery. Short-term outcomes for robotic surgeries are better, while long-term postoperative complication rates remain similar. However, there is a need for additional well-defined randomized control trials conducted across multiple centers to validate the use of robotic surgery over open and laparoscopic approaches. Improving patient care and outcomes is the objective of this comprehensive literature overview on surgical approaches for CRC.

Cancer Vaccines Based on Fluorine-Modified KH-1 Elicit Robust Immune Response

KH-1 is a tumor-associated carbohydrate antigen (TACA), which serves as a valuable target of antitumor vaccines for cancer immunotherapies. However, most TACAs are thymus-independent antigens (TD-Ag), and they tend to induce immunological tolerance, leading to their low immunogenicity. To overcome these problems, some fluorinated derivatives of the KH-1 antigen were designed, synthesized, and conjugated to the carrier protein CRM197 to form glycoconjugates, which were used for immunological studies with Freund's adjuvant. The results showed that fluorine-modified N-acyl KH-1 conjugates can induce higher titers of antibodies, especially IgG, which can recognize KH-1-positive cancer cells and can eliminate cancer cells through complement-dependent cytotoxicity (CDC). The trifluoro-modified KH-1-TF-CRM197 showed great potential as an anticancer vaccine candidate.

Novel Genetic and Epigenetic Biomarkers of Prognostic and Predictive Significance in Stage II/III Colorectal Cancer

The therapeutic strategies of stage II/III colorectal cancer (CRC) patients after curative surgery remain controversial. In the clinical decision-making process, oncologists need to answer questions such as whether adjuvant chemotherapy is necessary or which therapeutic regimen should be given to each patient. At present, whether adjuvant chemotherapy should be applied is primarily based on histopathological features and clinical risk factors. However, only a fraction of patients can benefit from it. More rigorous stratifying biomarkers are urgently needed to help further distinguishing these populations of patients. Recent progress in next-generation sequencing and high-throughput technologies has greatly promoted biomarker discovery as well as our understanding of the underlying mechanisms in CRC. Novel genetic and epigenetic biomarkers that are associated with prognosis or therapeutic responses have emerged. In this review, we discuss the strategies of biomarker discovery and summarize the status and assess the utility of previously published biomarkers in CRC.

Directed Evolution of Therapeutic Antibodies Targeting Glycosylation in Cancer

Simple Summary

We generated a platform for designing optimized functional therapeutic antibodies against cancer glycans. The target tumor-associated carbohydrate antigen is commonly expressed in colon and pancreatic cancers. We developed a system for selection of potent antibodies by yeast surface display against this carbohydrate antigen, then showed that elite clones have potent affinity, specificity, cancer cell binding, and therapeutic efficacy. These tools have broad utility for manipulating and engineering antibodies against carbohydrate antigens, and provide major innovative avenues of research in the field of cancer therapy and diagnostics.

Abstract

Glycosylation patterns commonly change in cancer, resulting in expression of tumor-associated carbohydrate antigens (TACA). While promising, currently available anti-glycan antibodies are not useful for clinical cancer therapy. Here, we show that potent anti-glycan antibodies can be engineered to acquire cancer therapeutic efficacy. We designed yeast surface display to generate and select for therapeutic antibodies against the TACA SLe^a (CA19−9) in colon and pancreatic cancers. Elite clones showed increased affinity, better specificity, improved binding of human pancreatic and colon cancer cell lines, and increased complement-dependent therapeutic efficacy. Molecular modeling explained the structural basis for improved antibody functionality at the molecular level. These new tools of directed molecular evolution and selection for effective anti-glycan antibodies, provide insights into the mechanisms of cancer therapy targeting glycosylation, and provide major methodological advances that are likely to open up innovative avenues of research in the field of cancer theranostics.

Early Assessment of Colorectal Cancer by Quantifying Circulating Tumor Cells in Peripheral Blood: ECT2 in Diagnosis of Colorectal Cancer

Circulating tumor cells (CTCs) in peripheral blood is an indication of poor prognosis for patients with different cancer types. However, most of the available technologies for detecting CTCs show low sensitivity and specificity. Therefore, we attempted to find an alternative marker for CTCs of colorectal cancer. We have directly extracted RNA from CTCs contained in 1.5 mL peripheral blood from 90 colorectal cancer patients and 151 healthy donors, and screened these samples for candidate marker genes by nested real-time quantitative polymerase chain reaction (PCR). From genes selected from a public database of microarray analyses, we successfully identified epithelial cell transforming sequence 2 oncogene (ECT2) as a gene that exhibits high differential expression ratios (p < 0.01). ECT2 displays good sensitivity and specificity, with an area under the curve (AUC) value of 0.821. This marker gene also has a high detection rate in patients with serum carcinoembryonic antigen (CEA) concentrations below the diagnostic threshold of 5 ng/mL. The expression of ECT2 can therefore serve as an alternative measurement that can compensate for the inadequacy of the current CEA test in the diagnosis and monitoring of colorectal cancer patients.

Elevated Serum Carcinoembryonic Antigen Is Associated with a Worse Survival Outcome of Patients After Liver Resection for Hepatocellular Carcinoma: a Propensity Score Matching Analysis

BACKGROUND

The relationship between serum carcinoembryonic antigen (CEA) and postoperative prognosis in hepatocellular carcinoma (HCC) has not been reported.

METHODS

Data of 5410 consecutive HCC patients who underwent hepatectomy was retrospectively reviewed. Survival curves for overall survival (OS) and tumor recurrence (TR) were depicted using the Kaplan-Meier method and compared using the log-rank test. Independent risk factors of OS and TR were analyzed with Cox hazard regression model. Besides, a one-to-one propensity score-matched (PSM) subset was performed to reduce selection bias. Subgroup analysis was done according to hepatitis B virus (HBV) infection or not.

RESULTS

Serum CEA ≥5.1 μg/L was an independent risk factor of OS and TR in the entire cohort and PSM subset (OS-hazard ratio = 1.218, 95 % confidence interval = 1.060-1.400; 1.383, 1.133-1.688, respectively; TR-1.256, 1.114-1.417; 1.258, 1.067-1.484, respectively). Subgroup analysis showed that CEA ≥5.1 μg/L was an independent risk factor of OS and TR in the HBV infection group (OS-1.234, 1.065-1.429; TR-1.231, 1.083-1.399) but not in the non-HBV infection group (OS-1.376, 0.895-2.117; TR-1.437, 0.989-2.088).

CONCLUSION

Serum CEA ≥5.1 μg/L was an independent risk factor of OS and TR of HCC patients, and patients with CEA ≥5.1 μg/L had poorer prognosis, especially for HCC patients with HBV infection.

Superior Immunologic and Therapeutic Efficacy of a Xenogeneic Genetic Cancer Vaccine Targeting Carcinoembryonic Human Antigen

We have generated a xenogeneic vaccine against human carcinoembryonic antigen (hCEACAM-5 or commonly hCEA) using as immunogen rhesus CEA (rhCEA). RhCEA cDNA was codon-usage optimized (rhCEAopt) and delivered by sequential DNA electro-gene-transfer (DNA-EGT) and adenoviral (Ad) vector. RhCEAopt was capable to break tolerance to CEA in hCEA transgenic mice and immune responses were detected against epitopes distributed over the entire length of the protein. Xenovaccination with rhCEA resulted in the activation of CD4+ T-cell responses in addition to self-reactive CD8+ T-cells, the development of high-titer antibodies against hCEA, and significant antitumor effects upon challenge with hCEA+ tumor cells. The superior activity of rhCEAopt compared with hCEAopt was confirmed in hCEA/HHD double-transgenic mice, where potent CD8+ T-cell responses against specific human HLA A*0201 hCEA epitopes were detected. Our data show that xenogeneic gene-based vaccination with rhCEA is a viable approach to break tolerance against CEA, thus suggesting further development in the clinical setting.

MEDULLARY THYROID CANCER THAT STAINS NEGATIVE FOR CA 19-9 HAS DECREASED METASTATIC POTENTIAL

OBJECTIVE

Presently, no clinical tools are available to diagnose the metastatic potential of medullary thyroid cancer (MTC) at disease presentation. Surveillance with calcitonin (Ct) and carcinoembryonic antigen (CEA) is currently recommended for the observation and diagnosis of metastatic disease after initial treatment of MTC. Recently, carbohydrate antigen (CA)19-9 staining has been associated with aggressive forms of MTC and metastatic spread. This pilot study explored whether positive CA19-9 staining of MTC tissue is associated with its metastatic potential.

METHODS

Sixteen cases of MTC were identified, and tissue specimens were immunostained for CA 19-9 and other MTC tumor markers. Clinical information about patients' MTC was collected through a retrospective chart review.

RESULTS

Overall, 63% of the specimens stained positive for CA19-9. The median size of positively staining specimens was 2.6 cm (interquartile range [IQR] 1.2-3.2) compared to 0.7 cm (0.5-1.2) in negatively staining MTC specimens (P = .04). All specimens from patients diagnosed with stage IV MTC stained positive for CA19-9, compared to only 40% of cases that were classified as stages I to III (P = .03). Furthermore, 100% of the primary specimens that were documented to have metastatic spread stained positive for CA19-9. The sensitivity for ruling out stage IV MTC based on negative staining for CA 19-9 was 100%.

CONCLUSION

Based on these results, we conclude that negative staining of MTC for CA19-9 may be associated with its decreased metastatic potential.

Translating clinical research of Molecular Biology into a personalized, multidisciplinary approach of colorectal cancer patients

Although multimodal treatment has brought important benefit, there is still great heterogeneity regarding the indication and response to chemotherapy in Stage II and III, and individual variations related to both overall survival and toxicity of new therapies in metastatic disease or tumor relapse. Recent research in molecular biology led to the development of a large scale of genetic biomarkers, but their clinical use is not concordant with the high expectations. The Aim of this review is to identify and discuss the molecular markers with proven clinical applicability as prognostic and/or predictive factors in CRC and also to establish a feasible algorithm of molecular testing, as routine practice, in the personalized, multidisciplinary approach of colorectal cancer patients in our country. Despite the revolution that occurred in the field of molecular marker research, only Serum CEA, Immunohistochemical analysis of mismatch repair proteins and PCR testing for KRAS and BRAF mutations have confirmed their clinical utility in the management of colorectal cancer. Their implementation in the current practice should partially resolve some of the controversies related to this heterogenic pathology, in matters of prognosis in different TNM stages, stage II patient risk stratification, diagnosis of hereditary CRC and likelihood of benefit from anti EGFR therapy in metastatic disease. The proposed algorithms of molecular testing are very useful but still imperfect and require further validation and constant optimization.

Aberrant glycosylation as biomarker for cancer: focus on CD43

Glycosylation is a posttranslational modification of proteins playing a major role in cell signalling, immune recognition, and cell-cell interaction because of their glycan branches conferring structure variability and binding specificity to lectin ligands. Aberrant expression of glycan structures as well as occurrence of truncated structures, precursors, or novel structures of glycan may affect ligand-receptor interactions and thus interfere with regulation of cell adhesion, migration, and proliferation. Indeed, aberrant glycosylation represents a hallmark of cancer, reflecting cancer-specific changes in glycan biosynthesis pathways such as the altered expression of glycosyltransferases and glycosidases. Most studies have been carried out to identify changes in serum glycan structures. In most cancers, fucosylation and sialylation are significantly modified. Thus, aberrations in glycan structures can be used as targets to improve existing serum cancer biomarkers. The ability to distinguish differences in the glycosylation of proteins between cancer and control patients emphasizes glycobiology as a promising field for potential biomarker identification. In this review, we discuss the aberrant protein glycosylation associated with human cancer and the identification of protein glycoforms as cancer biomarkers. In particular, we will focus on the aberrant CD43 glycosylation as cancer biomarker and the potential to exploit the UN1 monoclonal antibody (UN1 mAb) to identify aberrant CD43 glycoforms.

Synthesis and immunological evaluation of self-adjuvanting MUC1-macrophage activating lipopeptide 2 conjugate vaccine candidates

The synthesis and immunological evaluation of self-adjuvanting cancer vaccine candidates comprising of mucin 1 (MUC1) (glyco)peptides linked to macrophage activating lipopeptide 2 (MALP2) is described.

Carbohydrate biomarker recognition using synthetic lectin mimics

Carbohydrate biomarkers play very important roles in a wide range of biological and pathological processes. Compounds that can specifically recognize a carbohydrate biomarker are useful for targeted delivery of imaging agents and for development of new diagnostics. Furthermore, such compounds could also be candidates for the development of therapeutic agents. A tremendous amount of active work on synthetic lectin mimics has been reported in recent years. Amongst all the synthetic lectins, boronic-acid-based lectins (boronolectins) have shown great promise. Along this line, four classes of boronolectins including peptide-, nucleic-acid-, polymer-, and small-molecule-based ones are discussed with a focus on the design principles and recent advances. We hope that by presenting the potentials of this field, this review will stimulate more research in this area.

CEA-Related CAMs

The carcinoembryonic antigen (CEA) family comprises a large number of cellular surface molecules, the CEA-related cell adhesion molecules (CEACAMs), which belong to the Ig superfamily. CEACAMs exhibit a complex expression pattern in normal and malignant tissues. The majority of the CEACAMs are cellular adhesion molecules that are involved in a great variety of distinct cellular processes, for example in the integration of cellular responses through homo- and heterophilic adhesion and interaction with a broad selection of signal regulatory proteins, i.e., integrins or cytoskeletal components and tyrosine kinases. Moreover, expression of CEACAMs affects tumor growth, angiogenesis, cellular differentiation, immune responses, and they serve as receptors for commensal and pathogenic microbes. Recently, new insights into CEACAM structure and function became available, providing further elucidation of their kaleidoscopic functions.

Recent advances in developing synthetic carbohydrate-based vaccines for cancer immunotherapies

Cancer cells can often be distinguished from healthy cells by the expression of unique carbohydrate sequences decorating the cell surface as a result of aberrant glycosyltransferase activity occurring within the cell; these unusual carbohydrates can be used as valuable immunological targets in modern vaccine designs to raise carbohydrate-specific antibodies. Many tumor antigens (e.g., GM2, Ley, globo H, sialyl Tn and TF) have been identified to date in a variety of cancers. Unfortunately, carbohydrates alone evoke poor immunogenicity, owing to their lack of ability in inducing T-cell-dependent immune responses. In order to enhance their immunogenicity and promote long-lasting immune responses, carbohydrates are often chemically modified to link to an immunogenic protein or peptide fragment for eliciting T-cell-dependent responses. This review will present a summary of efforts and advancements made to date on creating carbohydrate-based anticancer vaccines, and will include novel approaches to overcoming the poor immunogenicity of carbohydrate-based vaccines.

Sequential two-step multienzyme synthesis of tumor-associated sialyl T-antigens and derivatives

A series of α2-3-sialylated β1-3-linked galactosides, including sialyl T-antigens, 3'-sialyl galacto-N-biose, 3'-sialyl lacto-N-biose, and their derivatives containing natural and non-natural sialic acid forms have been synthesized from simple monosaccharides using an efficient sequential two-step multienzyme approach.

A lectin affinity workflow targeting glycosite-specific, cancer-related carbohydrate structures in trypsin-digested human plasma

Glycans are cell-type-specific, posttranslational protein modifications that are modulated during developmental and disease processes. As such, glycoproteins are attractive biomarker candidates. Here, we describe a mass spectrometry-based workflow that incorporates lectin affinity chromatography to enrich for proteins that carry specific glycan structures. As increases in sialylation and fucosylation are prominent among cancer-associated modifications, we focused on Sambucus nigra agglutinin (SNA) and Aleuria aurantia lectin (AAL), lectins which bind sialic acid- and fucose-containing structures, respectively. Fucosylated and sialylated glycopeptides from human lactoferrin served as positive controls, and high-mannose structures from yeast invertase served as negative controls. The standards were spiked into Multiple Affinity Removal System (MARS) 14-depleted, trypsin-digested human plasma from healthy donors. Samples were loaded onto lectin columns, separated by HPLC into flow-through and bound fractions, and treated with peptide: N-glycosidase F to remove N-linked glycans. The deglycosylated peptide fractions were interrogated by ESI HPLC-MS/MS. We identified a total of 122 human plasma glycoproteins containing 247 unique glycosites. Importantly, several of the observed glycoproteins (e.g., cadherin 5 and neutrophil gelatinase-associated lipocalin) typically circulate in plasma at low nanogram per milliliter levels. Together, these results provide mass spectrometry-based evidence of the utility of incorporating lectin-separation platforms into cancer biomarker discovery pipelines.

Carbohydrate recognition by boronolectins, small molecules, and lectins

Carbohydrates are known to mediate a large number of biological and pathological events. Small and macromolecules capable of carbohydrate recognition have great potentials as research tools, diagnostics, vectors for targeted delivery of therapeutic and imaging agents, and therapeutic agents. However, this potential is far from being realized. One key issue is the difficulty in the development of "binders" capable of specific recognition of carbohydrates of biological relevance. This review discusses systematically the general approaches that are available in developing carbohydrate sensors and "binders/receptors," and their applications. The focus is on discoveries during the last 5 years.

Immunotherapy for cancer: synthetic carbohydrate-based vaccines

Aberrant glycosylation of glycoproteins and glycolipids of cancer cells, which correlates with poor survival rates, is being exploited for the development of immunotherapies for cancer. In particular, advances in the knowledge of cooperation between the innate and adaptive system combined with the implementation of efficient synthetic methods for assembly of oligosaccharides and glycopeptides is providing avenues for the rationale design of vaccine candidates. In this respect, fully synthetic vaccine candidates show great promise because they incorporate only those elements requires for relevant immune responses, and hence do not suffer from immune suppression observed with classical carbohydrate-protein conjugate vaccines. Such vaccines are chemically well-defined and it is to be expected that they can be produced in a reproducible fashion. In this feature article, recent advances in the development of fully synthetic sub-unit carbohydrate-based cancer vaccines will be discussed.

The prevalence and nature of glycan alterations on specific proteins in pancreatic cancer patients revealed using antibody-lectin sandwich arrays

Changes to the glycan structures of proteins secreted by cancer cells are known to be functionally important and to have potential diagnostic value. However, an exploration of the population variation and prevalence of glycan alterations on specific proteins has been lacking because of limitations in conventional glycobiology methods. Here we report the use of a previously developed antibody-lectin sandwich array method to characterize both the protein and glycan levels of specific mucins and carcinoembryonic antigen-related proteins captured from the sera of pancreatic cancer patients (n = 23) and control subjects (n = 23). The MUC16 protein was frequently elevated in the cancer patients (65% of the patients) but showed no glycan alterations, whereas the MUC1 and MUC5AC proteins were less frequently elevated (30 and 35%, respectively) and showed highly prevalent (up to 65%) and distinct glycan alterations. The most frequent glycan elevations involved the Thomsen-Friedenreich antigen, fucose, and Lewis antigens. An unexpected increase in the exposure of alpha-linked mannose also was observed on MUC1 and MUC5ac, indicating possible N-glycan modifications. Because glycan alterations occurred independently from the protein levels, improved identification of the cancer samples was achieved using glycan measurements on specific proteins relative to using the core protein measurements. The most significant elevation was the cancer antigen 19-9 on MUC1, occurring in 19 of 23 (87%) of the cancer patients and one of 23 (4%) of the control subjects. This work gives insight into the prevalence and protein carriers of glycan alterations in pancreatic cancer and points to the potential of using glycan measurements on specific proteins for highly effective biomarkers.

Increasing the antigenicity of synthetic tumor-associated carbohydrate antigens by targeting Toll-like receptors

SYNTHETIC CANCER VACCINES: A number of fully synthetic vaccine candidates have been designed, chemically synthesized, and immunologically evaluated to establish a strategy to overcome the poor immunogenicity of tumor-associated carbohydrates and glycopeptides and to determine the importance of Toll-like receptor (TLR) engagement for antigenic responses against these compounds.Epithelial cancer cells often overexpress mucins that are aberrantly glycosylated. Although it has been realized that these compounds offer exciting opportunities for the development of immunotherapy for cancer, their use is hampered by the low antigenicity of classical immunogens composed of a glycopeptide derived from a mucin conjugated to a foreign carrier protein. We have designed, chemically synthesized, and immunologically evaluated a number of fully synthetic vaccine candidates to establish a strategy to overcome the poor immunogenicity of tumor-associated carbohydrates and glycopeptides. The compounds were also designed to allow study of the importance of Toll-like receptor (TLR) engagement for these antigenic responses in detail. We have found that covalent attachment of a TLR2 agonist, a promiscuous peptide T-helper epitope, and a tumor-associated glycopeptide gives a compound (1) that elicits in mice exceptionally high titers of IgG antibodies that recognize MCF7 cancer cells expressing the tumor-associated carbohydrate. Immunizations with glycolipopeptide 2, which contains lipidated amino acids instead of a TLR2 ligand, gave significantly lower titers of IgG antibodies; this demonstrates that TLR engagement is critical for optimum antigenic responses. Although mixtures of compound 2 with Pam(3)CysSK(4) (3) or monophosphoryl lipid A (4) elicited titers of IgG antibodies similar to those seen with 1, the resulting antisera had impaired ability to recognize cancer cells. It was also found that covalent linkage of the helper T-epitope to the B-epitope is essential, probably because internalization of the helper T-epitope by B-cells requires assistance of the B-epitope. The results presented here show that synthetic vaccine development is amenable to structure-activity relationship studies for successful optimization of carbohydrate-based cancer vaccines.

Prognostic value of carcinoembryonic antigen distribution in tumor tissue of colorectal carcinoma

CONTEXT: Carcinoembryonic antigen (CEA) can be detected in colorectal tumor tissue but its role in the survival of patients remains controversial. OBJECTIVE: To characterize the expression of tissue CEA using immunohistochemical staining in colorectal tumors and to analyze the relationship between this finding and preoperative plasmatic level of CEA, morphologic features and survival of patients operated with curative intent for colorectal carcinoma. METHOD: Forty-seven patients were included in the study: 18 (38.3%) males and 29 (61.7%) females, with a mean age of 67.8 ± 9.7 years (37 to 84 years). Immediately before laparotomy, pre-operative serum levels of CEA were obtained where normal levels were considered <2.5 ng/mL for non-smokers, and <5.0 ng/mL for smokers. CEA immunohistochemical studies were carried out using anti-human CEA monoclonal mouse antibody. The expression of immunostaining for each neoplasia was classified according to the pattern of CEA tissular distribution into apical or cytoplasmic. The variables considered for the statistical analysis were plasmatic preoperative CEA level, location of the lesion within the large intestine, lesion diameter, lymph node involvement, Duke's classification, vein invasion, grade of cellular differentiation, survival and pattern of CEA tissular distribution. The statistical models utilized were Spearman's correlation and the Mann-Whitney, Kruskal-Wallis and Student t tests. Patients' survival was analyzed using the Kaplan-Meier method. RESULTS: The mean preoperative CEA value was 15.4 ± 5.5 ng/mL (0.2 to 92.1 ng/mL). The neoplasm was located in the colon in 29 (61.7%) and in the rectum in 18 (38.3%) patients. Eight (17.0%) patients were classified as Duke's stage A, 22 (46.8%) as stage B and 17 (36.2%) as stage C. On immunohistochemical studies, the pattern of CEA tissular distribution was apical in 33 (70.2%) patients and cytoplasmic in 14 (29.8%) patients. Patients with apical patterns presented a mean sera CEA level of 15.5 ± 6.5 ng/mL while those with cytoplasmic pattern attained a mean sera CEA level of 15.1 ± 7.3 ng/mL, with no significant difference between these values (P = 0.35). Apical distribution of CEA occurred in 6 (12.8%) Duke A, 18 (38.2%) Duke B and 9 (12.2%) Duke C patients, while cytoplasmic CEA tissular distribution was observed in 2 (4.2%) Duke A, 3 (6.4%) Duke B and 9 (19.1%) Duke C patients. Patients with Duke B neoplasms presented significantly more apical CEA tissular distribution patterns (P = 0.049) than subjects with cytoplasmic CEA tissular patterns. The apical CEA tissular distribution pattern in neoplasms was significantly more frequent in neoplasms with no lymph node compromise compared to the cytoplasmic pattern (P = 0.50). However, no significant differences were seen between apical and cytoplasmic CEA tissular distribution patterns in terms of colon or rectal site (P = 0.21), lesion diameter across greatest axis (P = 0.19), vein invasion (P = 0.13) or degree of cellular differentiation (P = 0.19). Of the 47 patients operated, 33 (70.2%) survived for more than 5 years where mean survival was 31.1 ± 5.6 months. Survival between patients with apical and cytoplasmic CEA tissular distribution showed no significant difference (P = 0.38). CONCLUSIONS: Although the apical distribution pattern of CEA was significantly more frequent in more advanced stages of Duke's classification, the CEA tissular distribution presented no relationship with serum CEA levels, morphological features of the neoplasm or survival of patients undergoing curative colorectal carcinoma resection.

Immunogenicity and safety of a DNA prime/adenovirus boost vaccine against rhesus CEA in nonhuman primates

Scaling up experimental protocols from rodents to humans is often not a straightforward procedure, and this particularly applies to cancer vaccines, where vaccination technology must be especially effective to overcome a variety of immune suppressive mechanisms. DNA electroporation (DNA-EP) and adenoviral vectors (Ad) have shown high potency and therapeutic efficacy for different antigens in several pre-clinical models. To evaluate the ability of DNA-EP and Ad to break tolerance to a self-antigen in large animals, we have cloned the CEA homologue (rhCEA) from rhesus monkeys (Macaca mulatta) colon tissue samples. rhCEA is a 705 aa protein and shares 78.9% homology to human CEA protein. Immunogenicity of rhCEA expressing vectors was tested in mice and subsequently in rhesus monkeys. To further increase the immunogenic potency of these vectors, a synthetic codon optimized rhCEA cDNA (rhCEAopt) was constructed. Genetic vaccination of rhesus monkeys was effective in breaking immune tolerance to rhCEA in all immunized animals, maintaining over time the elicited immune response, and most importantly, neither autoimmunity nor other side-effects were observed upon treatment. Our data confirm the efficacy of genetic cancer vaccines in large animals such as nonhuman primates and show that development of modified expression cassettes that result in increased potency of plasmid DNA and adenovirus may have a significant impact on vaccine development against malignancies expressing tumor associated antigens in patients.

Synthesis of a dimeric Lewis antigen and the evaluation of the epitope specificity of antibodies elicited in mice

The Lewis(y)-Lewis(x) heptasaccharide, modified by an artificial aminopropyl spacer, was synthesized by an approach that employed two orthogonally protected lactosamine building blocks. A p-(benzoyl)-benzyl glycoside was used as a novel anomeric protecting group, which could be selectively removed at a late stage in the synthesis, thus offering the benefit of enhanced flexibility. The artificial aminopropyl moiety was modified by a thioacetyl group, which allowed an efficient conjugation to keyhole limpet hemocyanin (KLH) that had been activated with electrophilic 3-(bromoacetamido)-propionyl groups. Mice were immunized with the Le(y)Le(x)-BrAc-KLH antigen. Analysis of the sera by ELISA established that a strong helper T-cell immune response was raised against the Le(y)Le(x) saccharide. Further ELISA analysis showed that the titer for monomeric Le(y) tetrasaccharide was tenfold lower whereas recognition of the Le(x) trisaccharide was negligible.

A highly conserved His-His motif present in alpha1-->3/4fucosyltransferases is required for optimal activity and functions in acceptor binding

Alpha1-->3/4fucosyltransferases (FucTs) from several species contain a highly conserved His-His motif adjacent to an enzyme region correlating with the ability to catalyze fucose transfer to type 1 chain acceptors. Site-directed mutagenesis has been employed to analyze structure-function relationships of this His-His motif in human FucT-IV. The results indicate that most changes of His(113) and His(114) and nearby residues of FucT-IV reduced the specific activity of the enzymes. Analysis of acceptor properties demonstrated close similarity of most mutants with wild-type FucT-IV, whereas an apparent preference for the H-type II acceptor was observed for the His(114) mutants. Kinetic studies demonstrated that mutants of His(114) had a substantially increased K(m) for acceptor compared to other enzymes tested. The dramatic increase in acceptor K(m) for the His(114) mutants, particularly for the nonfucosylated acceptor, suggests that this His-His motif is involved in acceptor binding and perhaps interacts with GlcNAc residues of type 2 acceptors. The presence of fucose in acceptor substrates may promote more efficient substrate binding and presumably partially overcomes the weaker interaction with GlcNAc caused by the mutation.

Universal tumor antigens as targets for immunotherapy

BACKGROUND

Clinically successful Ag-specific cancer immunotherapy depends on the identification of tumor-rejection Ags. Historically, tumor Ags have been identified by analyzing cancer patients' own T-cell or Ab responses.

METHODS

The unveiling of the human genome and optimized immunological analytical tools, particularly 'reverse immunology', have made it possible to screen any given protein for immunogenic epitopes. These advances enable the immunological characterization of universal tumor-associated gene products that mediate critical functions for tumor growth and development.

RESULTS

Four examples of candidate universal tumor Ags reviewed here include the telomerase reverse transcriptase (hTERT), the inhibitor of apoptosis survivin, the p53-interacting protein MDM2, and the cytochrome P450 isoform 1B1--each at various levels of preclinical and clinical development.

DISCUSSION

The cardinal feature of universal TAA is that they are expressed in (nearly) all tumors and in no normal tissues. They are directly involved in the malignant phenotype of the tumor. Certain peptides derived from such Ags are expressed on the tumor-cell surface, as evidenced by Ag-specific, MHC-restricted T-cell anti-tumor reactivity in vitro. It is hoped that these features imply a pre-existing, high-affinity T-cell pool that can be activated in vivo in patients, without immunoselection of variant tumor cells no longer expressing the Ag of choice.

Cell surface fucose ablation as a therapeutic strategy for malignant neoplasms

The sugar alpha-L-fucose is overexpressed in many human malignancies, especially on specific glycoproteins, glycolipids, certain mucins, and putative cell adhesion ligands found on cancer cell surfaces. Many of these molecules are known or suspected mediators of cell-cell adhesion, cell signaling, motility, or invasion. As knowledge of fucose metabolism evolves and specific mechanisms of its distribution and incorporation are more exactly documented, modulation of fucose expression in cancer is becoming increasingly more feasible. The authors propose that cancer cell surface alpha-L-fucose is a logical target for selective therapeutic ablation. Reduction of fucose content on the surfaces of malignant cells should effectively cripple the cells' physiologic functions by altering or dysregulating cell-cell or cell-matrix interactions, critical for maintaining the malignant phenotype. Significant therapeutic benefits might include modulation of adhesion abnormalities in the cancer cells, reduction of cancer cell motility or invasiveness, reexposure to immune surveillance, or a combination of these events.

A GDP-fucose-protected, pyridoxal-5'-Phosphate/NaBH(4)-sensitive lys residue common to human alpha1-->3Fucosyltransferases corresponds to Lys(300) in FucT-IV

Human alpha1-->3/4fucosyltransferases (FucTs) contain a common essential pyridoxal-5'-phosphate(PLP)/NaBH(4) reactive, GDP-fucose-protectable Lys. For identification, site-directed mutants at lysines of FucT-IV and -VII were prepared and tested. Non conserved lysine mutants K119Y and K394Q were similar to wild-type FucT-IV. However, mutants of conserved lysines K228R and K300R were distinct. The specific activity of K228R was 2- to 3-fold lower but retained K(m) values for donor and acceptor substrates as wild-type FucT-IV. The specific activity of K300R was reduced over 400-fold with an apparent K(m) for GDP-fucose over 200 microM. FucT-VII mutants K169R and K240R (equivalent to K228R and K300R for FucT-IV, respectively) were inactive. No change in PLP/NaBH(4) sensitivity occurred with K119Y, K228R, and K394Q compared to wild-type FucT-IV. These and previous results (A. L. Sherwood, A. T. Nguyen, J. M. Whitaker, B. A. Macher, M. R. Stroud, and E. H. Holmes, J. Biol. Chem. 273, 25256-25260, 1998) demonstrate that of three conserved lysines in FucT-IV, two (Lys(228) and Lys(283)) are not involved in substrate binding but perhaps in catalysis. The third site, Lys(300), is involved in GDP-fucose binding and PLP/NaBH(4) inactivation.