Colorectal cancer vaccines in clinical trials

Clinicopathological significance of intelectin-1 in colorectal cancer: Intelectin-1 participates in tumor suppression and favorable progress

Intelectin-1 (ITLN1) is an adipokine with an anti-inflammatory function that is involved in neoplastic diseases such as pleural mesothelioma and gastric and prostate cancers. However, the expression and function of ITLN1 in colorectal cancer (CRC) remain unknown. To identify novel prognostic markers or therapeutic targets for CRC, we focused on ITLN1 protein. By immunohistochemistry, 87 (59%) of 148 CRC cases showed reduced expression of ITLN1. ITLN1-reduced CRC cases were associated with higher M grades (P = 0.0017) than ITLN1-retained CRC cases. Furthermore, the cases with ITLN1 retained expression tended toward a more favorable prognosis than those with reduced expression. Cell growth of the CRC cell lines transfected with ITLN1 siRNA were greater than those of the negative control cell lines transfected with siRNA. Levels of phosphorylated epidermal growth factor receptor, Erk and Akt were higher in the CRC cells transfected with ITLN1 siRNA than in control cells. Immunohistochemical analysis of human colorectal polyp specimens also revealed a sequential decrease in the expression of ITLN1 through both the conventional adenoma-carcinoma pathway and the serrated pathway. These results indicated that ITLN1 might play an important role in regulating colorectal tumorigenesis.

Strategies for developing and optimizing cancer vaccines

With the spotlight on cancer immunotherapy and the expanding use of immune checkpoint inhibitors, strategies to improve the response rate and duration of current cancer immunotherapeutics are highly sought. In that sense, investigators around the globe have been putting spurs on the development of effective cancer vaccines in humans after decades of efforts that led to limited clinical success. In more than three decades of research in pursuit of targeted and personalized immunotherapy, several platforms have been incorporated into the list of cancer vaccines from live viral or bacterial agents harboring antigens to synthetic peptides with the hope of stronger and durable immune responses that will tackle cancers better. Unlike adoptive cell therapy, cancer vaccines can take advantage of using a patient's entire immune system that can include more than engineered receptors or ligands in developing antigen-specific responses. Advances in molecular technology also secured the use of genetically modified genes or proteins of interest to enhance the chance of stronger immune responses. The formulation of vaccines to increase chances of immune recognition such as nanoparticles for peptide delivery is another area of great interest. Studies indicate that cancer vaccines alone may elicit tumor-specific cellular or humoral responses in immunologic assays and even regression or shrinkage of the cancer in select trials, but novel strategies, especially in combination with other cancer therapies, are under study and are likely to be critical to achieve and optimize reliable objective responses and survival benefit. In this review, cancer vaccine platforms with different approaches to deliver tumor antigens and boost immunity are discussed with the intention of summarizing what we know and what we need to improve in the clinical trial setting.

Self-antigen MASH2 combined with the AS15 immunostimulant induces tumor protection in colorectal cancer mouse models

Human achaete scute homolog 2 (HASH2) and its murine ortholog MASH2 are potential targets for colorectal cancer immunotherapy. We assessed immunogenicity and antitumor potential of recombinant MASH2 protein combined with AS15 immunostimulant (recMASH2+AS15) in CB6F1 and Apc^+/Min-FCCC mice. CB6F1 mice received 4 injections of recMASH2+AS15 or AS15 alone before challenge with TC1-MASH2 tumor cells (Tumor Challenge). Apc^+/Min-FCCC mice received 9 injections of recMASH2+AS15 or vehicle (phosphate buffer saline [PBS] or AS15 alone), before (two independent Prophylactic Studies) or after (Immunotherapy) colon adenomas were detectable by colonoscopy. CB6F1 mice immunized with recMASH2+AS15 had a significantly smaller mean tumor size and improved survival rate compared to controls (104 mm² vs. 197 mm² [p = 0.009] and 67% vs. 7% [p = 0.001], respectively). In Prophylactic Study 1, the mean number of colon adenomas was significantly lower in Apc^+/Min-FCCC mice receiving recMASH2+AS15 compared to PBS (1.8 [95% confidence interval 1.0–3.3] vs. 5.2 [3.7–7.4], p = 0.003). Fewer microadenomas were observed in recMASH2+AS15 groups compared to PBS in both Prophylactic Studies (Study 1: mean 0.4 [0.2–1.0] vs. 1.5 [0.9–2.4], p = 0.009; Study 2: 0.4 [0.2–0.6] vs. 1.1 [0.8–1.5], p = 0.001). In the Immunotherapy Study, fewer colon adenomas tended to be observed in recMASH2+AS15-treated mice (4.1 [2.9–6.0]) compared to controls (AS15 4.7 [3.3–6.6]; PBS 4.9 [3.5–6.9]; no significant difference). recMASH2+AS15 induced MASH2-specific antibody and CD4+ responses in both mouse models. recMASH2+AS15 partially protected mice against MASH2-expressing tumors and reduced spontaneous colorectal adenomas in Apc^+/Min-FCCC mice, indicating that MASH2/HASH2 antigens are targets for colorectal cancer immunotherapy.

Elevated Gab2 induces tumor growth and angiogenesis in colorectal cancer through upregulating VEGF levels

Background

Grb2-associated binder 2 (Gab2) is a scaffolding protein that serves as a critical signaling amplifier downstream of tyrosine kinase receptors. Our previous study has shown that Gab2 induces epithelial-to-mesenchymal transition (EMT) and promotes metastasis in colorectal cancer (CRC). However, the role of Gab2 in CRC growth and angiogenesis remains unclear.

Methods

The expression of vascular endothelial growth factor (VEGF) in different colorectal tissues was detected by immunohistochemistry and qRT-PCR to evaluate its correlation with Gab2. Lentiviral vectors bearing Gab2 gene and its small interfering RNAs were constructed and transfected into CRC cell lines. The effects of Gab2 on the cell proliferation in vitro and tumorigenesis in vivo, were examined via CCK‑8 assay, colony formation assay as well as tumorigenicity assay respectively. Moreover, to assess its potential role in tumor growth and angiogenesis, the expression of Ki67, CD34 and vascular endothelial growth factor receptor-2 (VEGFR2) were detected by immunohistochemistry in CRC cells tumors. Finally, we evaluated the impact of Gab2 on the expression of c-Myc and VEGF, and the probable effect of mechanistic targeted extracellular signal-regulated kinase (ERK) pathway in suppressing tumor growth and angiogenesis.

Results

Up-regulation of Gab2 expression was found to be positively correlated with VEGF in CRC tissues. Exogenous expression of Gab2 obviously promoted, whereas silencing of Gab2 inhibited, proliferation and clone formation of human CRC cells in vitro. Of note, Gab2 enhanced tumorigenesis and tumor growth in mouse xenografts with high Ki67 expression, and led to an increased vessel density with strong CD34 and VEGFR2 activity. In addition, elevated Gab2 expression obviously up-regulated the expression of VEGF, and stimulated the activation of its downstream genes, ERK1/2 and c-Myc in CRC cells. Instead, down-regulated Gab2 expression significantly reduced the levels of VEGF, and inhibited the transduction of ERK/c-Myc pathway. Finally, we revealed that mechanistic target of mitogen-activated protein kinase (MEK) could attenuate Gab2-induced tumor growth and angiogenesis via altering VEGF and c-Myc levels.

Conclusions

The results from our study suggest that Gab2 promotes intestinal tumor growth and angiogenesis through upregulation of VEGF expression mediated by the MEK/ERK/c-Myc pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-017-0524-2) contains supplementary material, which is available to authorized users.

Investigation of phosphorylated adjuvants co-encapsulated with a model cancer peptide antigen for the treatment of colorectal cancer and liver metastasis

The lipid calcium phosphate nanoparticle is a versatile platform capable of encapsulating a wide range of phosphorylated molecules from single nucleotides to pDNA. The use of this platform has shown great success as an immunotherapeutic vaccine carrier, capable of delivering co-encapsulated phosphorylated adjuvants and peptides. Three potent vaccine formulations were investigated for anti-cancer efficacy. The phosphorylated adjuvants, CpG, 2'3'cGAMP, and 5'pppdsRNA were co-encapsulated with a model phosphorylated tumor specific peptide antigen (p-AH1-A5). The anti-cancer efficacy of these adjuvants was assessed using an orthotopic colorectal liver metastasis model based on highly aggressive and metastatic CT-26 FL3 cells implanted into the cecum wall. The results clearly indicate that the RIG-1 ligand, 5'pppdsRNA, co-encapsulated with the p-AH1-A5 peptide antigen greatly reduced the growth rate of the primary colon cancer as well as arrested the establishment of liver metastasis in comparison to the other adjuvant formulations and unvaccinated controls. Further evaluation of the immune cell populations within the primary tumor confirms the ability of the 5'pppdsRNA adjuvant to boost the adaptive CD8+ T-cell population, while not inciting increased populations of immune suppressive cell types such as T-regulatory cells or myeloid derived suppressor cells. Furthermore, to our knowledge this is the first study to investigate the anti-cancer efficacy of a specific RIG-1 receptor ligand, 5'pppdsRNA, alongside more established TLR 9 (CpG) and STING (2'3'cGAMP) adjuvants in a cancer vaccine. The 5'pppdsRNA vaccine formulation can be a potent immunotherapy, especially when combined with agents that remodel the immune suppressive microenvironment of the tumor.

Clinicopathological significance of SPC18 in colorectal cancer: SPC18 participates in tumor progression

Colorectal cancer (CRC) is one of the leading causes of cancer‐related death worldwide. In order to identify novel prognostic markers or therapeutic targets for CRC, we searched for candidate genes in our comprehensive gene expression libraries, and focused on SEC11A, which encodes the SPC18 protein. SPC18 plays a key role in the endoplasmic reticulum‐Golgi secretory pathway and presumably regulates the secretion of various secretory proteins. An immunohistochemical analysis of SPC18 in 137 CRC tissue samples demonstrated that 79 (58%) CRC cases were positive for SPC18. SPC18‐positive CRC cases were more advanced in terms of N classification (P = 0.0315) and tumor stage (P = 0.0240) than SPC18‐negative CRC cases. Furthermore, the expression of SPC18 was an independent prognostic classifier for CRC patients. The cell growth and invasiveness of SPC18 siRNA‐transfected CRC cell lines was less than that of the negative control siRNA‐transfected cell lines. The levels of phosphorylated epidermal growth factor receptor, Erk and Akt were lower in SPC18 siRNA‐transfected CRC cells than in control cells. The expression of SPC18 was colocalized with β‐catenin nuclear localization and MMP7 at the invasive front. An immunohistochemical analysis of human colorectal polyp specimens revealed a sequential increase in the expression of SPC18 through the conventional adenoma‐carcinoma pathway, while SPC18 was not expressed or was expressed to a lesser extent in serrated pathway‐related tumors. These results suggest that SPC18 is involved in tumor progression, and is an independent prognostic classifier in patients with CRC.

Tumor Immuno-Environment in Cancer Progression and Therapy

The approvals of Provenge (Sipuleucel-T), Ipilimumab (Yervoy/anti-CTLA-4) and blockers of the PD-1 - PD-L1/PD-L2 pathway, such as nivolumab (Opdivo), pembrolizumab (Keytruda), or atezolizumab (Tecentriq), have established immunotherapy as a key component of comprehensive cancer care. Further, murine mechanistic studies and studies in immunocompromised patients have documented the critical role of immunity in effectiveness of radio- and chemotherapy. However, in addition to the ability of the immune system to control cancer progression, it can also promote tumor growth, via regulatory T cells (Tregs), myeloid-derived dendritic cells (MDSCs) and tumor associated macrophages (TAM), which can enhance survival of cancer cells directly or via the regulation of the tumor stroma.An increasing body of evidence supports a central role for the tumor microenvironment (TME) and the interactions between tumor stroma, infiltrating immune cells and cancer cells during the induction and effector phase of anti-cancer immunity, and the overall effectiveness of immunotherapy and other forms of cancer treatment. In this chapter, we discuss the roles of key TME components during tumor progression, metastatic process and cancer therapy-induced tumor regression, as well as opportunities for their modulation to enhance the overall therapeutic benefit.

The Immunogenicity of Colorectal Cancer in Relation to Tumor Development and Treatment

Although most cancer types have been viewed as immunologically silent until recently, it has become increasingly clear that the immune system plays key roles in the course of tumor development. Remarkable progress towards understanding cancer immunogenicity and tumor-immune system interactions has revealed important implications for the design of novel immune-based therapies. Natural immune responses, but also therapeutic interventions, can modulate the tumor phenotype due to selective outgrowth of resistant subtypes. This is the result of heterogeneity of tumors, with genetic instability as a driving force, and obviously changes the immunogenicity of tumors. In this review, we discuss the immunogenicity of colorectal cancer (CRC) in relation to tumor development and treatment. As most tumors, CRC activates the immune system in various ways, and is also capable of escaping recognition and elimination by the immune system. Tumor-immune system interactions underlie the balance between immune control and immune escape, and may differ in primary tumors, in the circulation, and in liver metastases of CRC. Since CRC immunogenicity varies between tumors and individuals, novel immune-based therapeutic strategies should not only anticipate the molecular profile, but also the immunological profile of a specific tumor.

Gab2 facilitates epithelial-to-mesenchymal transition via the MEK/ERK/MMP signaling in colorectal cancer

Background

Grb2-associated binder 2 (Gab2), a scaffolding adaptor protein, has recently been implicated in cancer progression. However, the role of Gab2 in the progression and metastasis of colorectal cancer (CRC) remains unclear.

Methods

Gab2 expression was assessed in CRC patient specimens as well as in CRC cell lines. Recombinant lentivirus vector containing Gab2 gene and its small interfering RNAs were constructed and introduced into CRC cells. Cell migration and invasion ability were evaluated by transwell assays in vitro, and in vivo metastasis was performed on nude mice model. Moreover, the expression of Gab2 and epithelial-to-mesenchymal transition (EMT)-associated proteins (E-cadherin and vimentin) were assessed by western blot and qRT-PCR in CRC cells to evaluate the correlation between Gab2 and EMT. Finally, we evaluated the impact of Gab2 on the activation of its downstream signaling effectors, and furthermore the effects of these pathways on Gab2 induced-EMT were also detected.

Results

We confirmed that increased Gab2 expression correlated with higher tumor node metastasis stage and highly invasive CRC cell lines. Ectopic expression of Gab2 promoted metastasis of CRC cells, whereas silencing of Gab2 resulted in inhibited metastasis both in vitro and in vivo. Overexpression of Gab2 in CRC cells induced EMT, whereas knockdown of Gab2 had the opposite effect. Furthermore, upregulation of Gab2 expression obviously stimulated the activation of extracellular signal-regulated kinase-1/2 (ERK1/2), and increased the expression of matrix metalloproteinase-7 (MMP7) and matrix metalloproteinase-9 (MMP9) in CRC cells. Conversely, downregulation of Gab2 expression significantly decreased the activation of ERK1/2, and inhibited MMP7 and MMP9 expression. U0126, an inhibitor of mitogen-activated protein kinase (MEK), can reverse the effects of Gab2 on EMT.

Conclusions

Our work highlights that Gab2 induces EMT through the MEK/ERK/MMP pathway, which in turn promotes intestinal tumor metastasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-015-0280-0) contains supplementary material, which is available to authorized users.

Nemo‑like kinase expression predicts poor survival in colorectal cancer

Nemo‑like kinase (NLK), a serine/threonine protein kinase, was previously reported to be associated with tumor proliferation and invasion. The present study aimed to evaluate whether NLK participates in the tumorigenesis and progression of colorectal cancer (CRC). NLK expression was examined using reverse transcription quantitative polymerase chain reaction (RT‑qPCR) and western blot analysis in 50 paired CRC tissues as well as immunohistochemical analysis of 406 cases of primary CRC tissues and paired non‑cancerous tissues. Correlations between NLK expression, the clinicopathological features of CRC patients and clinical outcome were then analyzed. NLK expression was found to be significantly higher in CRC tissues as well as associated with the depth of tumor invasion, lymph node metastasis, distant metastasis, histological differentiation, vascular invasion and advanced tumor stage. Patients with NLK‑positive tumors demonstrated higher rates of recurrence and mortality than patients with NLK‑negative tumors. Multivariate analyses revealed that NLK expression was an independent factor for overall survival [hazard ratio (HR)=0.035; 95% confidence interval (CI)=0.02‑0.19; P<0.001] and disease‑free survival (HR=0.033; 95% CI=0.007‑0.09; P<0.001) in CRC patients. In conclusion, the results of the present study indicated that NLK may serve as a novel biomarker for tumor recurrence and survival for CRC patients.

Phase II study of personalized peptide vaccination for previously treated advanced colorectal cancer

The prognosis of advanced colorectal cancer (aCRC) remains poor, and development of new therapeutic approaches, including immunotherapy, is needed urgently. Herein we report on our phase II study of personalized peptide vaccination (PPV) in 60 previously treated patients with aCRC, who had failed at least one regimen of standard chemotherapy and/or targeted therapy. For PPV, a maximum of four HLA-matched peptides were individually selected from a pool of 31 different peptide candidates based on preexisting host immunity, and administered subcutaneously without severe adverse events. Boosting of IgG and cytotoxic T lymphocyte (CTL) responses specific to the administered peptides was observed in 49% and 63%, respectively, of the patients, who completed the first cycles of six vaccinations. Median overall survival (OS) time was 498 days, with 1- and 2-year survival rates of 53% and 22%, respectively. Multivariate Cox regression analysis of prevaccination factors showed that plasma IL6, IP-10, and BAFF levels were significantly prognostic for OS [hazard ratio (HR), 1.508, P = 0.043; HR, 1.579, P = 0.024; HR, 0.509, P = 0.002, respectively]. In addition, increased peptide-specific CTL responses after vaccination were significantly predictive of favorable OS (HR, 0.231; P = 0.021), suggesting a causal relationship between biologic and clinical efficacy of PPV. On the basis of the safety profile and potential clinical efficacy, we believe that clinical trials of PPV would be warranted for previously treated patients with aCRC.

PPM1D is a prognostic marker and therapeutic target in colorectal cancer

Protein phosphatase, Mg²⁺/Mn²⁺ dependent, 1D (PPM1D) has been associated with carcinogenesis. The present study investigated PPM1D expression as a potential biomarker in colorectal cancer (CRC). PPM1D expression was assessed using immunohistochemistry in 368 patients with CRC. The correlation between PPM1D expression, clinicopathological features and prognosis was analyzed. PPM1D small interfering (si)RNA-induced PPM1D silencing was performed in CRC cell lines to assess the effect of PPM1D on tumor cell proliferation and invasion in vitro. A total of 68.48% (252/368) of the CRC samples displayed high PPM1D expression. By contrast, only 9.24% (34/368) of the matched non-cancerous tissue samples exhibited high PPM1D expression. High PPM1D expression was correlated with node metastasis (P=0.0024), distant metastasis (P<0.001) and TNM stage (P=0.0016). Kaplan-Meier survival analysis revealed that patients with low PPM1D expression had significantly longer survival than those with high PPM1D expression (P=0.012). Moreover, multivariate analyses demonstrated that high PPM1D expression was an independent prognostic factor for overall survival (hazard ratio = 0.24; 95% confidence interval, 0.13–0.86; P=0.004). Furthermore, PPM1D gene silencing was found to significantly reduce the proliferation and invasion of CRC cells in vitro. These findings suggest a role for PPM1D as a prognostic marker and potential therapeutic target in CRC.

The prognostic impact of human leukocyte antigen (HLA) class I antigen abnormalities in salivary gland cancer. A clinicopathological study of 288 cases

AIMS

To study abnormalities of proteins of the major histocompatibility complex class I in a series of 288 salivary gland carcinomas, and to correlate findings with patients' overall survival (OS).

METHODS AND RESULTS

Protein expression of human leukocyte antigen (HLA)-A, heavy chain (HC)-10, β2 -microglobulin, low molecular weight polypeptides (LMP) 2 and 7, transporters associated with antigen processing (TAP) 1 and 2, calnexin, calreticulin, endoplasmic reticulum (ER) p57 and tapasin was evaluated by immunohistochemistry and semiquantitatively analyzed. As compared with normal salivary gland tissue, HLA-A, LMP7, TAP2 and HLA class I were significantly down-regulated in salivary gland carcinomas, whereas β2 -microglobulin, calnexin, LMP2, and TAP1 were upregulated. Expression of calreticulin, ERp57 and tapasin was unaltered. In univariate Kaplan-Meier analyses, low expression of LMP7 (P = 0.005) and high expression of β2 -microglobulin (P = 0.028), HLA-A (P < 0.001), TAP1 (P = 0.01), and tapasin (P < 0.001) were significantly associated with shorter OS. In multivariate analysis incorporating tumour stage, nodal/distant metastasis, and grade, HLA-A (P = 0.014), LMP7 (P = 0.033), and tapasin (P = 0.024), as well as distant metastasis (P = 0.012) and high tumour grade (P < 0.001), remained statistically significant.

CONCLUSION

The prognostic influence of up-regulated HLA-A and tapasin and down-regulated LMP7 may provide a rationale for targeting these specific components of the antigen processing and presentation pathway in salivary gland carcinomas.

Recent progress in canine tumor vaccination: potential applications for human tumor vaccines

Tumor vaccination holds great promise for the treatment of cancer and research concerning tumor vaccination in dogs is of great interest for veterinary as well as human medicine. Indeed, cancer is the leading cause of death in adult dogs and companion animals are acknowledged as excellent preclinical models for human oncology. The license of the veterinary melanoma vaccine (Oncept™) and Provenge® for the treatment of prostate cancer in men established tumor vaccination as a valid treatment modality for cancer. Although the results with this and other vaccines are promising, there are still some hurdles to overcome. In this article, preclinical and clinical trials with tumor vaccines in dogs are discussed, as well as the surplus value of canine cancer patients for human medicine.

Addition of interferon-α to the p53-SLP® vaccine results in increased production of interferon-γ in vaccinated colorectal cancer patients: a phase I/II clinical trial

We previously established safety and immunogenicity of a p53 synthetic long peptides (p53-SLP®) vaccine. In the current trial, we investigated whether combination of interferon-alpha (IFN-α) with p53-SLP® is both safe and able to improve the induced p53-specific IFN-γ response. Eleven colorectal cancer patients successfully treated for metastatic disease were enrolled in this study. Of these, nine patients completed follow-up after two injections with p53-SLP® together with IFN-α. Safety and p53-specific immune responses were determined before and after vaccination. Furthermore, cryopreserved PBMCs were compared head-to-head to cryopreserved PBMCs obtained in our previous trial with p53-SLP® only. Toxicity of p53-SLP® vaccination in combination with IFN-α was limited to Grade 1 or 2, with predominantly small ongoing swellings at the vaccination site. All patients harbored p53-specific T cells after vaccination and most patients showed p53-specific antibodies. Compared to the previous trial, addition of IFN-α significantly improved the frequency of p53-specific T cells in IFN-γ ELISPOT. Moreover, in this trial, p53-specific T cells were detectable in blood samples of all patients in a direct ex vivo multiparameter flowcytometric assay, opposed to only 2 of 10 patients vaccinated with p53-SLP® only. Finally, patients in this trial displayed a broader p53-specific immunoglobulin-G response, indicating an overall better p53-specific T-helper response. Our study shows that p53-SLP® vaccination combined with IFN-α injection is safe and capable of inducing p53-specific immunity. When compared to a similar trial with p53-SLP® vaccination alone the combination was found to induce significantly more IFN-γ producing p53-specific T cells.

T-cell-inducing vaccines - what's the future

In the twentieth century vaccine development has moved from the use of attenuated or killed micro-organisms to protein sub-unit vaccines, with vaccine immunogenicity assessed by measuring antibodies induced by vaccination. However, for many infectious diseases T cells are an important part of naturally acquired protective immune responses, and inducing these by vaccination has been the aim of much research. The progress that has been made in developing effective T-cell-inducing vaccines against viral and parasitic diseases such as HIV and malaria is discussed, along with recent developments in therapeutic vaccine development for chronic viral infections and cancer. Although many ways of inducing T cells by vaccination have been assessed, the majority result in low level, non-protective responses. Sufficient clinical research has now been conducted to establish that replication-deficient viral vectored vaccines lead the field in inducing strong and broad responses, and efficacy studies of T-cell-inducing vaccines against a number of diseases are finally demonstrating that this is a valid approach to filling the gaps in our defence against not only infectious disease, but some forms of cancer.