BAP31, a promising target for the immunotherapy of malignant melanomas

The molecular mechanism of on-demand sterol biosynthesis at organelle contact sites

Contact-sites are specialized zones of proximity between two organelles, essential for organelle communication and coordination. The formation of contacts between the Endoplasmic Reticulum (ER), and other organelles, relies on a unique membrane environment enriched in sterols. However, how these sterol-rich domains are formed and maintained had not been understood. We found that the yeast membrane protein Yet3, the homolog of human BAP31, is localized to multiple ER contact sites. We show that Yet3 interacts with all the enzymes of the post-squalene ergosterol biosynthesis pathway and recruits them to create sterol-rich domains. Increasing sterol levels at ER contacts causes its depletion from the plasma membrane leading to a compensatory reaction and altered cell metabolism. Our data shows that Yet3 provides on-demand sterols at contacts thus shaping organellar structure and function. A molecular understanding of this protein's functions gives new insights into the role of BAP31 in development and pathology.

BAP31-Mediated miR-206/133b Cluster Promotes Transendothelial Migration and Metastasis of Colorectal Cancer

Dysregulated B cell receptor-associated protein 31 (BAP31) plays a crucial role in tumor progression. This study aimed to investigate the functions and molecular mechanism of BAP31 on the miR-206/133b cluster in colorectal cancer (CRC). qPCR was conducted to detect miRNA and mRNA levels in tissues and cells. Western blot assays were used to assess the levels of biomarkers and targets, as well as the levels of BAP31 and HOXD10. Wound healing, coculture and transwell assays were conducted to assess the transendothelial migration abilities of CRC cells. A luciferase assay was employed to assess miRNA binding effects on targets, as well as the initiating transcription effect of genomic fragments. Tumor growth and lung metastatic models were established through an in vivo animal study. BAP31 overexpression in CRC cells led to a reduction in the expression of the miR-206/133b cluster. The expression of the miR-206/133b cluster was correlated with the transendothelial migration capability of CRC cells. The miR-206/133b cluster was found to directly regulate cell division cycle 42 (CDC42) and actin-related protein 2/3 complex subunit 5 (ARPC5) in the tight junction pathway (hsa04530). Moreover, a potential transcription regulator of the miR-206/133b cluster was also found to be Homeobox D10 (HOXD10). We further elucidated the molecular mechanisms and functional mechanisms of BAP31's regulatory role in the expression levels of the miR-206/133b cluster by inhibiting HOXD10 translocation from the cytoplasm to the nucleus. In conclusion, this study provides valuable insights into how BAP31 regulates the transcription of the miR-206/133b cluster and how BAP31-related lung metastases arise in CRC.

An Intrabody against B-Cell Receptor-Associated Protein 31 (BAP31) Suppresses the Glycosylation of the Epithelial Cell-Adhesion Molecule (EpCAM) via Affecting the Formation of the Sec61-Translocon-Associated Protein (TRAP) Complex

The epithelial cell-adhesion molecule (EpCAM) is hyperglycosylated in carcinoma tissue and the oncogenic function of EpCAM primarily depends on the degree of glycosylation. Inhibiting EpCAM glycosylation is expected to have an inhibitory effect on cancer. We analyzed the relationship of BAP31 with 84 kinds of tumor-associated antigens and found that BAP31 is positively correlated with the protein level of EpCAM. Triple mutations of EpCAM N76/111/198A, which are no longer modified by glycosylation, were constructed to determine whether BAP31 has an effect on the glycosylation of EpCAM. Plasmids containing different C-termini of BAP31 were constructed to identify the regions of BAP31 that affects EpCAM glycosylation. Antibodies against BAP31 (165-205) were screened from a human phage single-domain antibody library and the effect of the antibody (VH-F12) on EpCAM glycosylation and anticancer was investigated. BAP31 increases protein levels of EpCAM by promoting its glycosylation. The amino acid region from 165 to 205 in BAP31 plays an important role in regulating the glycosylation of EpCAM. The antibody VH-F12 significantly inhibited glycosylation of EpCAM which, subsequently, reduced the adhesion of gastric cancer cells, inducing cytotoxic autophagy, inhibiting the AKT-PI3K-mTOR signaling pathway, and, finally, resulting in proliferation inhibition both in vitro and in vivo. Finally, we clarified that BAP31 plays a key role in promoting N-glycosylation of EpCAM by affecting the Sec61 translocation channels. Altogether, these data implied that BAP31 regulates the N-glycosylation of EpCAM and may represent a potential therapeutic target for cancer therapy.

Preparation of antibodies against TXR1 and construction of a new DNA tumor vaccine

BACKGROUND

Taxol-resistance gene 1 (TXR1) is closely correlated with the paclitaxel resistance in the cancer chemotherapy. However, due to the lack of monoclonal antibodies (mAbs) with strong specificity and high sensitivity, little information is found about TXR1 target-related tumor therapy.

METHODS

We developed an TXR1 recombinant DNA vaccine by inserting TXR1 DNA sequence into lysosome-associated membrane protein 1 (LAMP1). Adaptive immune responses were assessed by indirect enzyme-linked immunosorbent assay (ELISA), Enzyme-linked immunospot test (ELISpot), and cytotoxic T-lymphocyte (CTL) cytotoxicity.

RESULTS

The pGEX4T-1-TXR1 reconstructed prokaryotic expression plasmid was constructed for producing high-purity TXR1 protein. Subsequently, a total of four mAbs for TXR1 and two PcAbs were successfully constructed and identified. We further found that TXR1 was highly expressed in breast cancer tissue than normal controls. Therefore, we constructed four tumor vectors, pVAX1-LAMP/TXR1, pVAX1-LAMP, pVAX1/TXR1 and pVAX1, for immunization. After three times of immunization, ELISpot data showed that single peptide 6,9,11 could stimulate T cells secreting IFN-γ in pVAX1-LAMP/TXR1 group. Moreover, the number of specific T cells and immune response effects significantly increased comparing to the pVAX1-LAMP control group. In addition, cytotoxicity showed that when the effect to target ratio was 40:l the killing effect of pVAX1-LAMP/TXR1 group was significantly higher than the pVAX1-TXR1 group.

CONCLUSION

Our results provides new evidence for the TXR1 related tumor immunology and aids the early prevention of cancer.

B-Cell Receptor-Associated Protein 31 Promotes Metastasis via AKT/β-Catenin/Snail Pathway in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most lethal cancer worldwide, characterized with high heterogeneity and inclination to metastasize. Emerging evidence suggests that BAP31 gets involved in cancer progression with different kinds. It still remains unknown whether and how BAP31 plays a role in HCC metastasis. Epithelial–mesenchymal transition (EMT) has been a common feature in tumor micro-environment, whose inducer TGF-β increased BAP31 expression in this research. Elevated expression of BAP31 was positively correlated with tumor size, vascular invasion and poor prognosis in human HCC. Ectopic expression of BAP31 promoted cell migration and invasion while BAP31 knockdown markedly attenuated metastatic potential in HCC cells and mice orthotopic xenografts. BAP31 induced EMT process, and enhanced the expression level of EMT-related factor Snail and decreased contents and membrane distribution of E-cadherin. BAP31 also activated AKT/β-catenin pathway, which mediated its promotional effects on HCC metastasis. AKT inhibitor further counteracted the activated AKT/β-catenin/Snail upon BAP31 over-expression. Moreover, silencing Snail in BAP31-overexpressed cells impaired enhanced migratory and invasive abilities of HCC cells. In HCC tissues, BAP31 expression was positively associated with Snail. In conclusion, BAP31 promotes HCC metastasis by activating AKT/β-catenin/Snail pathway. Thus, our study implicates BAP31 as potential prognostic biomarker, and provides valuable information for HCC prognosis and treatment.

B-cell receptor-associated protein 31 promotes migration and invasion in ovarian cancer cells

B cell receptor associated protein 31 (BAP31) is a member of the B cell receptor that functions as a transporter for numerous types of newly formed proteins from the endoplasmic reticulum to the Golgi apparatus. Previous studies found that that BAP31 serves an important role in the pathogenesis of malignancy but its specific effect on ovarian cancer is not clear. The present study aimed to investigate whether BAP31 affects ovarian cancer and its underlying mechanism. In the present study, ovarian cancer tissue, human ovarian normal epithelial cell line IOSE80 and five ovarian cancer cell lines (A2780, Hey-T30, COC1, SKOV3 and OVCAR3) underwent reverse transcription-quantitative PCR, western blotting, Cell Counting Kit-8, Transwell and co-immunoprecipitation (Co-IP) assay and transcriptome sequencing. Previous studies showed that compared with healthy tissues, the expression level of BAP31 protein was found to be significantly higher in various types of cancer tissues, implying that BAP31 may serve an important role in the pathogenesis of cancer. The present study found that BAP31 expression was upregulated in five ovarian cancer cell lines and ovarian cancer tissue, such that BAP31 knockdown [performed using two short hairpin (sh)RNA plasmids] decreased proliferation, invasion and migration. In addition, BAP31 knockdown was found to downregulate the expression of N-cadherin and upregulate the expression of E-cadherin on transcriptional level by controlling the nuclear aggregation of TWIST1, a transcriptional regulator of N-cadherin and E-cadherin. There was no interaction between BAP31 and E-cadherin or N-cadherin using Co-IP detection, while BAP31, E-cadherin and N-cadherin interacted with TWIST1 protein. E-cadherin and N-cadherin expression levels recovered when TWIST1 was overexpressed in the shBCAP31 cells. These results suggest that BAP31 can regulate the migration and invasion of ovarian cancer cells through the epithelial-mesenchymal transition pathway at the transcriptional level, which may be beneficial for the identification of potentially novel targets for ovarian cancer therapy.

BAP31: Physiological functions and roles in disease

B-cell receptor-associated protein 31 (BAP31 or BCAP31) is a ubiquitously expressed transmembrane protein found mainly in the endoplasmic reticulum (ER), including in mitochondria-associated membranes (MAMs). It acts as a broad-specificity membrane protein chaperone and quality control factor, which can promote different fates for its clients, including ER retention, ER export, ER-associated degradation (ERAD), or evasion of degradation, and it also acts as a MAM tetherer and regulatory protein. It is involved in several cellular processes - it supports ER and mitochondrial homeostasis, promotes proliferation and migration, plays several roles in metabolism and the immune system, and regulates autophagy and apoptosis. Full-length BAP31 can be anti-apoptotic, but can also mediate activation of caspase-8, and itself be cleaved by caspase-8 into p20-BAP31, which promotes apoptosis by mobilizing ER calcium stores at MAMs. BAP31 loss-of-function mutations is the cause of 'deafness, dystonia, and central hypomyelination' (DDCH) syndrome, characterized by severe neurological symptoms and early death. BAP31 is furthermore implicated in a growing number of cancers and other diseases, and several viruses have been found to target it to promote their survival or life cycle progression. The purpose of this review is to provide an overview and examination of the basic properties, functions, mechanisms, and roles in disease of BAP31.

Biological roles of the B cell receptor-associated protein 31: Functional Implication in Cancer

BAP31 is a ubiquitously expressed integral membrane protein of the endoplasmic reticulum. BAP31 is involved in various biological and molecular processes, including protein transport, viral processing, apoptosis signaling, MHC 1 antigen processing and presentation, mitochondria and ER calcium regulation, and proteasomal protein degradation. We employed a BAP31 interaction search using STRING and inBioMap™ protein-protein interaction networks, and the Metabolic Atlas, which revealed molecular and metabolic interactors involved in various pathways essential for cell growth, cell survival, and disease development. BAP31, as a chaperone and resident protein of the ER, was reported in the development of some central nervous system disorders and metabolic diseases about AD, ALS, and Liver disease. In addition, BAP31 is overexpressed in many cancers. Furthermore, research around BAP31 involvement in cancer has taken up a shape, focusing on its roles in cancer cell survival, disease prognosis, and targeted treatment. Here, we address published data on the Biological roles of BAP31 in both health and disease. We present an analytical description of BAP31 expression and functional implication in some human cancers and the impact of its expression and regulation while it models as a potential target in cancer therapy. Besides, a profound understanding of BAP31 is insightful of the gap between cancer development and neurodegeneration, thus generating novel ideas surrounding the link between the two different cell phenomena.

MiR-362 suppresses cervical cancer progression via directly targeting BAP31 and activating TGFβ/Smad pathway

BAP31 (B-cell receptor-associated protein 31) is an important regulator of intracellular signal transduction and highly expressed in several cancer tissues or testicular tissues. Our previous study had revealed that elevated BAP31 plays a crucial role in the progress and metastasis of cervical cancer. Even so, the precise mechanism of abnormal BAP31 elevation in cervical cancer has not been fully elucidated. We revealed that the expression of BAP31 was mainly regulated by microRNA-362 (miR-362), which was markedly downregulated in cervical cancer tissues and negatively correlated with clinical tumor staging. Overexpression of miR-362 inhibited cervical cancer cell proliferation and increased the proportion of apoptotic cells. Furthermore, miR-362 reduced the tumor sizes and prolonged mice survival time in xenograft nude mice model. Finally, we demonstrated that the BAP31/SPTBN1 complex regulated tumor progression through the Smad 2/3 pathway under the control of miR-362. Collectively, our findings demonstrated that miR-362 could work as an anti-oncomiR that inhibits proliferation and promotes apoptosis in cervical cancer cells via BAP31 and TGFβ/Smad pathway. Overexpression of miR-362 might be a potential therapeutic strategy for cervical cancer.

Immunohistochemical expression of BCAP 31 in chronic plaque psoriasis

Psoriasis is a common chronic skin inflammatory disease characterized by an exaggerated proliferation of keratinocytes. B-cell receptor-associated protein 31 (BCAP 31) plays critical roles in induction of proliferation and apoptosis. The current study aimed at evaluation of the immunohistochemical localization of BCAP 31 in psoriatic skin compared to normal skin in addition of correlating BCAP31 expression with the clinical and pathological parameters of psoriasis. The present study was carried out on skin biopsies from 30 psoriatic patients and 10 normal skin (control group). BCAP31 was not expressed in normal skin either epidermis or dermis, while it was expressed in epidermis of 15 psoriatic cases and in dermis of 13 cases with a significant difference between the two groups (p < .05). Strong epidermal BCAP 31 expression was associated with marked parakeratosis (p = .025). There was a significant co-parallel epidermal and dermal expression of BCAP31 in psoriasis (p < .05). The role of BCAP 31 is not only confined to its expression by affected keratinocytes but extended to its localization to dermal lymphocytes where they were correlated with each other. The up- regulation of BCAP 31 in psoriatic lesion compared to normal skin may suggest its use as a target therapy for treatment of psoriasis that necessitates further studies to clarify.

MicroRNA-362-3p Inhibits Migration and Invasion via Targeting BCAP31 in Cervical Cancer

Cervical cancer (CC) is the most common malignant tumor in gynecology, and metastasis is an important cause of patient death. MiRNAs (microRNAs) have been found to play key roles in cervical cancer metastasis, but the effect of miR-362-3p in CC is unclear. This study aimed to investigate the role of miR-362-3p in cervical cancer migration and invasion. We compared the expression levels of miR-362-3p in cervical cancer tissues and adjacent normal cervical tissues. In CC tissues, miR-362-3p expression was significantly down-regulated, which is related to the cancer stage and patient survival. MiR-362-3p can effectively inhibit the migration and invasion of cervical cancer cells. The dual-luciferase reporter assay results showed that BCAP31 (B cell receptor associated protein 31) is a direct target protein of miR-362-3p. The results of the immunohistochemical examination of clinical tissue samples showed that BCAP31 was abnormally highly expressed in cervical cancer, which was positively correlated with the clinical stage. BCAP31 knockdown exerted similar effects as miR-362-3p overexpression. Further GSEA analysis showed that BCAP31 may participate in multiple biological processes, such as protein transport, metabolism, and organelle organization. Our results suggest that miR-362-3p inhibits migration and invasion via directly targeting BCAP31 in cervical cancer, and restoring miR-362-3p levels may be a new treatment strategy for cervical cancer in the future.

BAP31 regulates IRAK1-dependent neuroinflammation in microglia

BACKGROUND

Microglia, the mononuclear immune cells of the central nervous system (CNS), are essential for the maintenance of CNS homeostasis. BAP31, a resident and ubiquitously expressed protein of the endoplasmic reticulum, serves as a sorting factor for its client proteins, mediating the subsequent export, retention, and degradation or survival. Recently, BAP31 has been defined as a regulatory molecule in the CNS, but the function of BAP31 in microglia has yet to be determined. In the present study, we investigated whether BAP31 is involved in the inflammatory response of microglia.

METHODS

This study used the BV2 cell line and BAP31 conditional knockdown mice generated via the Cre/LoxP system. A BAP31 knockdown experiment was performed to elucidate the role of BAP31 in the endogenous inflammatory cytokine production by microglial BV2 cells. A mouse model of lipopolysaccharide (LPS)-induced cognitive impairment was established to evaluate the neuroprotective effect of BAP31 against neuroinflammation-induced memory deficits. Behavioral alterations were assessed with the open field test (OFT), Y maze, and Morris water maze. The activation of microglia in the hippocampus of mice was observed by immunohistochemistry. Western blot, enzyme-linked immunosorbent assay (ELISA), immunofluorescence staining, and reverse transcription quantitative real-time polymerase chain reaction (RT-PCR) were used to clarify the mechanisms.

RESULTS

BAP31 deficiency upregulates LPS-induced proinflammatory cytokines in BV2 cells and mice by upregulating the protein level of IRAK1, which in turn increases the translocation and transcriptional activity of NF-κB p65 and c-Jun, and moreover, knockdown of IRAK1 or use of an IRAK1 inhibitor reverses these functions. In the cognitive impairment animal model, the BAP31 knockdown mice displayed increased severity in memory deficiency accompanied by an increased expression of proinflammatory factors in the hippocampus.

CONCLUSIONS

These findings indicate that BAP31 may modulate inflammatory cytokines and cognitive impairment induced by neuroinflammation through IRAK1, which demonstrates that BAP31 plays an essential role in microglial inflammation and prevention of memory deficits caused by neuroinflammation.

Cancer DNA vaccines: current preclinical and clinical developments and future perspectives

The recent developments in immuno-oncology have opened an unprecedented avenue for the emergence of vaccine strategies. Therapeutic DNA cancer vaccines are now considered a very promising strategy to activate the immune system against cancer. In the past, several clinical trials using plasmid DNA vaccines demonstrated a good safety profile and the activation of a broad and specific immune response. However, these vaccines often demonstrated only modest therapeutic effects in clinical trials due to the immunosuppressive mechanisms developed by the tumor. To enhance the vaccine-induced immune response and the treatment efficacy, DNA vaccines could be improved by using two different strategies. The first is to increase their immunogenicity by selecting and optimizing the best antigen(s) to be inserted into the plasmid DNA. The second strategy is to combine DNA vaccines with other complementary therapies that could improve their activity by attenuating immunosuppression in the tumor microenvironment or by increasing the activity/number of immune cells. A growing number of preclinical and clinical studies are adopting these two strategies to better exploit the potential of DNA vaccination. In this review, we analyze the last 5-year preclinical studies and 10-year clinical trials using plasmid DNA vaccines for cancer therapy. We also investigate the strategies that are being developed to overcome the limitations in cancer DNA vaccination, revisiting the rationale for different combinations of therapy and the different possibilities in antigen choice. Finally, we highlight the most promising developments and critical points that need to be addressed to move towards the approval of therapeutic cancer DNA vaccines as part of the standard of cancer care in the future.

MiR-451a suppressing BAP31 can inhibit proliferation and increase apoptosis through inducing ER stress in colorectal cancer

The global morbidity and mortality of colorectal cancer (CRC) are ranked the third among gastrointestinal tumors in the world. MiR-451a is associated with several types of cancer, including CRC. However, the roles and mechanisms of miR-451a in CRC have not been elucidated. BAP31 is a predicted target gene of miR-451a in our suppression subtractive hybridization library. Its relationship with miR-451a and function in CRC are unclear. We hypothesized that miR-451a could induce apoptosis through suppressing BAP31 in CRC. Immunohistochemistry and real-time PCR were used to measure BAP31 expressions in CRC tissues and pericarcinous tissues from 57 CRC patients and CRC cell lines. Dual-luciferase reporter assay was used to detect the binding of miR-451a to BAP31. The expression of BAP31 protein in CRC tissues was significantly higher than that in pericarcinous tissues, which was correlated with distant metastasis and advanced clinical stages of CRC patients. The expression of BAP31 was higher in HCT116, HT29, SW620, and DLD cells than that in the normal colonic epithelial cell line NCM460. The expression of BAP31 was absolutely down-regulated when over-expressing miR-451a in HCT116 and SW620 cells compared with control cells. Mir-451a inhibited the expression of BAP31 by binding to its 5'-UTR. Over-expressing miR-451a or silencing BAP31 suppressed the proliferation and apoptosis of CRC cells by increasing the expressions of endoplasmic reticulum stress (ERS)-associated proteins, including GRP78/BIP, BAX, and PERK/elF2α/ATF4/CHOP, which resulted in increased ERS, cytoplasmic calcium ion flowing, and apoptosis of CRC cells. These changes resulting from over-expressing miR-451a were reversed by over-expressing BAP31 with mutated miR-451a-binding sites. Over-expressing miR-451a or silencing BAP31 inhibited tumor growth by inducing ERS. The present study demonstrated that miR-451a can inhibit proliferation and increase apoptosis through inducing ERS by binding to the 5'-UTR of BAP31 in CRC.

Inhibition of BAP31 expression inhibits cervical cancer progression by suppressing metastasis and inducing intrinsic and extrinsic apoptosis

Cervical cancer is reported as one of the most lethal types of cancer among female. However, extensive studies of the molecular mechanisms that regulate the progression of cervical cancer are still required. B-cell associated protein (BAP)-31 is a 28-kDa integral membrane protein in the endoplasmic reticulum (ER), playing essential role in modulating various physiological processes. The present study indicated that BAP31 was a novel gene associated with cervical cancer development. Here, we demonstrated that BAP31 was significantly increased in human cervical cancer specimens, which was positively correlated to histological grade of the cancer. BAP31 knockdown suppressed cell proliferation, clonogenic ability and metastasis-associated traits in vitro, as well as carcinogenesis and pulmonary metastasis in vivo. Further studies indicated that the expression levels of transforming growth factor (TGF)-β1, matrix metalloproteinase (MMP)-2, MMP-9, Rho-associated protein kinase 1 (ROCK1), α-smooth muscle actin (α-SMA), Vimentin and N-cadherin were markedly reduced by BAP31 knockdown in cervical cancer cells. In addition, intrinsic and extrinsic apoptosis was significantly induced in BAP31 knockdown cells, as evidenced by the increased expression of cleaved Caspase-8/-9/-3 and poly (ADP-ribose) polymerases (PARP). Notably, suppressing the activities of Caspase-8/-9 and -3 obviously diminished BAP31 silence-triggered apoptosis. Together, these findings highlighted an essential role for BAP31 in the modulation of tumorigenesis and metastatic potential of cervical cancer, and demonstrated a promising application of BAP31 in cancer prevention.

BAP31, a newly defined cancer/testis antigen, regulates proliferation, migration, and invasion to promote cervical cancer progression

Malignant tumors typically undergo an atavistic regression characterized by the overexpression of embryonic genes and proto-oncogenes, including a variety of cancer/testis antigens (CTAs) that are testis-derived and are not expressed or expressed in trace amounts in somatic tissues. Based on this theory, we established a new method to identify unknown CTAs, the spermatogenic cells-specific monoclonal antibody-defined cancer/testis antigen (SADA) method. Using the SADA method, we identified BAP31 as a novel CTA and confirmed that BAP31 expression is associated with progression and metastasis of several cancers, particularly in cervical cancer. We found that BAP31 was significantly upregulated in stage I, II, and III cervical cancer patients and highly correlated with poor clinic outcomes. We further demonstrated that BAP31 regulates cervical cancer cell proliferation by arresting the cell cycle at the G0/G1 stage and that depletion of BAP31 inhibits hyper-proliferation. Moreover, depletion of BAP31 inhibits cervical cancer cell invasion and migration by regulating the expression and subcellular localization of Drebrin, M-RIP, SPECC1L, and Nexilin, and then affect the cytoskeleton assemblage. Finally, the depletion of BAP31 prevents cervical cancer progression and metastasis in vivo. These findings provide a new method for identifying novel CTAs as well as mechanistic insights into how BAP31 regulates cervical cancer hyper-proliferation and metastasis.

Inhibition of tumor growth by cancer vaccine combined with metronomic chemotherapy and anti-PD-1 in a pre-clinical setting

Tumor microenvironment (TME) is characterized by multiple immune suppressive mechanisms able to suppress anti-tumor effector cell immunity. Combinatorial strategies, including vaccine and immunomodulatory drugs, need to be developed for improved immunotherapy efficacy.

A novel combinatorial approach was assessed in C57BL/6 mice injected with mouse melanoma B16F10 cells. A multi-peptide vaccine (PEPT) was combined with a low dose metronomic chemotherapy (MCT) and an anti-PD-1 checkpoint inhibitor (CI). Statistical analysis were performed with the unpaired two-sided Student’s t-test and ANOVA.

Animals treated with the multi-peptide vaccine combined with MCT or CI showed remarkable delay in tumor growth and prolonged survival as compared to control groups. The multi-pronged combination including PEPT+MCT+CI was able to prolong survival in all mice and inhibit tumor growth in 66.6% of mice. All animals which did not show tumor growth were re-challenged with the same melanoma cells and one of them showed complete tumor growth inhibition. The anti-tumor effect was associated with strong T cell immune response to vaccine mutated peptides and significant reduction of regulatory T cells.

The combination of a vaccine with MCT and CI was highly efficient in potentiating the vaccine’s anti-tumor effects. The approach is highly promising to be moved into clinical trial.

Cancer: Untethering Mitochondria from the Endoplasmic Reticulum?

Following the discovery of the mitochondria-associated membrane (MAM) as a hub for lipid metabolism in 1990 and its description as one of the first examples for membrane contact sites at the turn of the century, the past decade has seen the emergence of this structure as a potential regulator of cancer growth and metabolism. The mechanistic basis for this hypothesis is that the MAM accommodates flux of Ca²⁺ from the endoplasmic reticulum (ER) to mitochondria. This flux then determines mitochondrial ATP production, known to be low in many tumors as part of the Warburg effect. However, low mitochondrial Ca²⁺ flux also reduces the propensity of tumor cells to undergo apoptosis, another cancer hallmark. Numerous regulators of this flux have been recently identified as MAM proteins. Not surprisingly, many fall into the groups of tumor suppressors and oncogenes. Given the important role that the MAM could play in cancer, it is expected that proteins mediating its formation are particularly implicated in tumorigenesis. Examples for such proteins are mitofusin-2 and phosphofurin acidic cluster sorting protein 2 that likely act as tumor suppressors. This review discusses how these proteins that mediate or regulate ER–mitochondria tethering are (or are not) promoting or inhibiting tumorigenesis. The emerging picture of MAMs in cancer seems to indicate that in addition to the downregulation of mitochondrial Ca²⁺ import, MAM defects are but one way how cancer cells control mitochondria metabolism and apoptosis.

Antibody response to HER2 extracellular domain and subdomains in mouse following DNA immunization

Human epidermal growth factor receptor 2 (HER2) is overexpressed in 15-20 % of breast cancer patients and is an appropriate target for immunotherapy in these patients. Monoclonal antibodies (mAbs) specific to HER2 are currently applied to treat breast cancer patients with HER2 overexpression. Active immunization with HER2 DNA or protein has been considered as a suitable alternative. The aim of this study is to evaluate anti-HER2 antibody response in serum of mice immunized with DNA constructs containing full extracellular domain (fECD) or subdomains of human HER2. Four extracellular subdomains and also fECD of HER2 were cloned into pCMV6-Neo vector. Different groups of Balb/C mice were immunized with HER2 DNA constructs and boosted with HER2 recombinant protein. The anti-HER2 antibody was subsequently determined by ELISA, flow cytometry, and immunohistochemistry. Anti-HER2 antibody was detected only in serum of mice immunized with fECD DNA. None of HER2 extracellular subdomains induced appreciable levels of anti-HER2 antibody. However, boosting with fECD or extracellular subdomain III (DIII) recombinant protein resulted in enhanced anti-HER2 fECD as well as anti-HER2 subdomain antibody responses. In this regard, almost all (99 %) of HER2-overexpressing BT474 cells could be detected by serum antibody from mice immunized with HER2 subdomain DNA and boosted with recombinant HER2 protein by flow cytometry. Similarly, serum of mice immunized with DIII DNA construct and boosted with recombinant DIII protein could also recognize these cells, but to a lesser extent (50 %). Our findings suggest that combination of HER2 DNA and protein immunization could effectively induce anti-HER2 antibody response in Balb/C mice.