Cloning and soluble expression of mature alpha-luffin from Luffa cylindrica and its antitumor activities in vitro

Recombinant pebulin protein, a type 2 ribosome-inactivating protein isolated from dwarf elder (Sambucus ebulus L.) shows anticancer and antifungal activities in vitro

In this study, encoding sequence of a new type 2 RIP (pebulin) was isolated and cloned from dwarf elder (Sambucus ebulus L.) native to the northern regions of Iran. The nucleotide sequence of pebulin was ligated to the pET-28a(+) expression plasmid and cloned into the E. coli strain BL21 (DE3) in order to express heterologously of recombinant protein. The recombinant pebulin protein was mainly produced in the form of insoluble inclusion bodies probably because to absence of N-glycosylation process in E. coli. Therefore, in order to increase the expression of recombinant protein in soluble form, co-expression of the target protein with the pG-Tf2 chaperone plasmid and incubation of bacterial culture under low temperature were used to enhance solubility and accumulation of recombinant protein. After purification of the recombinant protein using affinity chromatography method, the bioactivity of pebulin was analyzed by hemagglutination, anticancer, and antifungal assays. The results of the hemagglutination assay showed that purified pebulin agglutinated erythrocytes in all human blood groups. In addition, pebulin considerably inhibited the proliferation of cancer cell lines MCF-7 and HT-29 in a time- and dose-dependent manner and indicated remarkably growth-inhibiting effect against the plant pathogenic fungi such as Alternaria solani and Fusarium oxysporum.

Cytotoxic and Apoptotic Effects of Luffa Cylindrica Leaves Extract against Acute Lymphoblastic Leukemic Stem Cells

BACKGROUND

Acute lymphoblastic leukemia (ALL) is an aggressive malignancy defined by accumulation of lymphoblasts in the bone marrow. Leukemic stem cells (LSCs) are the major cause of the recurrence and metastasis of ALL. This study aimed to develop an effective anti-cancer agent targeting these LSCs. Luffa Cylindrica (L.C.) leaves extract was selected to evaluate its effect on ALL via eradicating the LSCs as it contains many active anti-cancer flavonoids.

METHODS

Thirty-two bone marrow samples of ALL patients were used in this study. LSCs population was identified in the selected samples. Cell viability was measured by MTT assay and flow cytometry. Cell cycle, apoptosis, proliferation marker; ki-67 and colony forming assay were further analyzed.

RESULTS

This study revealed the expression of CD34+/CD38+ cells in addition to CD34+/CD38- population and the extract was effective against the two LSCs populations. MTT assay showed that treated leukemic cells exhibited significant reduction in the viable cells in a dose dependent manner with IC50 of 3 µg/µl which was then confirmed by flow cytometry. Cell cycle analysis results showed significant reduction in the percentage of cells treated with L.C. extract in both the S and G0/G1 phases, with concomitant increase in the G2/M phase. Also, L.C. extract could effectively induce apoptosis, inhibit proliferation and suppress colonogenecity of leukemic cells.

CONCLUSION

This study validated the medicinal potential of L.C. leaves extract as a promising anti-leukemic agent targeting both LSCs and blasts in ALL patients, which may be explained by the synergy found between its potent flavonoids especially apigenin, luteolin and kaempferol.

Cytotoxic effect of aqueous ethanolic extract of Luffa cylindrica leaves on cancer stem cells CD44+/24- in breast cancer patients with various molecular sub-types using tissue samples in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Luffa cylindrica (L.) M.Roem is a climbing plant its parts have been used as traditional medicine for the treatment of different types of diseases including diarrhea, inflammation, cancer and viral infections. The parts used include fruit, seeds and leaves.

AIM OF THE STUDY

Our study aims to investigate the effect of the aqueous-ethanol extract of Luffa cylindrica leaves on breast cancer stem cells CD44⁺/24^- and other cell sub-populations using clinical samples with different molecular sub-types of breast cancer in vitro.

MATERIALS AND METHODS

Breast tissues were obtained from patients undergoing surgery for the removal of breast tumors after complete clinical and pathological investigations. Tissue samples were processed to cell suspensions and treated with the extract in the tissue culture laboratory. Percentages of cell sub-populations within tumors and viability were measured by flowcytometry using clusters of differentiation as cell markers.

RESULTS

Our results revealed that there were decreases in the total cell viability, CD44⁺/24^- and total CD24⁺ cell sub-populations percentages after treatment with the extract, this may be an important indication of using Luffa leaves extract in the treatment of breast cancer or in combination with the traditional treatments.

CONCLUSION

Luffa cylindrica has proven to have anticancer activity on three different subtypes of breast cancer including luminal A, luminal B and Her2/neu enriched more over it has cytotoxic effect on both bulk tumor cells as well as cancer stem cells sub population CD44⁺/24^- which possess high tumorigenic potency, these results were confirmed by measuring their viable number after treatment and sphere formation assay results.

Cytotoxicity of Luffa cylindrica (L.) M.Roem. extract against circulating cancer stem cells in hepatocellular carcinoma

ETHNOPHARMACOLOGICAL RELEVANCE

Luffa cylindrica (L.) M.Roem. has been recognized as traditional medicine for the treatment of various diseases like inflammatory diseases, diarrhea and viral infections. The usual parts used include fruit, seeds and leaves.

AIM OF THE STUDY

To evaluate the anticancer activity of the hot water extract of the whole plant of Luffa cylindrica using circulating tumor cells and cancer stem cells isolated from the peripheral blood of hepatocellular carcinoma patients in vitro.

MATERIALS AND METHODS

Seventy five adult patients who reported as stage II and III Hepatocellular carcinoma were selected. Blood samples were withdrawn and the circulating tumor cells were isolated from the whole blood. Tumor cells and cancer stem cells were detected and isolated by flow cytometric techniques. The isolated cell types were cultured and propagated in the tissue culture facility, the extract was tested on the isolated cells.

RESULTS

Luffa cylindrica hot water extract has shown cytotoxic activity against circulating tumor cells of hepatocellular carcinoma especially the cells sub-population CD133⁺/CD44⁺ with little effect among CD133⁺/CD44^- sub-population.

CONCLUSION

Hot water extract of Luffa cylindrica whole plant could decrease the ratio of cancer stem cells in blood of HCC patients and may be used to minimize recurrence and metastasis in hepatocellular carcinoma patients.

Chemical Composition of Aqueous Ethanol Extract of Luffa cylindrica Leaves and Its Effect on Representation of Caspase-8, Caspase-3, and the Proliferation Marker Ki67 in Intrinsic Molecular Subtypes of Breast Cancer in Vitro

Breast cancer constitutes the second most prevalent cancer in Egypt, the problem needs more trends in treatment and treatment development either by regimen modification or introducing new drugs, and the main objective of this study is to screen the effects of the aqueous ethanol herbal extract of Luffa cylindrica leaves on different types of breast cancer cell lines representing different molecular subtypes of the disease. The major active constituents of the extract were tentatively identified by LC/MS which revealed the presence of phenolic compound derivatives and saponin that may be responsible in part for the activity of the extract. The emphasis was laid on the main apoptotic pathways as well as the extract effect on the normal cell line. Results of phytochemical investigation, cell cycle analysis, and molecular analysis of apoptotic and proliferative markers have shown effective anticancer activity against MCF-7, BT-474, and MDA-MB-231 cell lines which represent three subtypes of breast cancer, luminal A, luminal B, and triple negative, respectively. On the other hand, the effects on normal lung fibroblast cell line are less prominent at the dose used for treating breast cancer cell lines.

Optimization of EnBase Fed-Batch Cultivation to Improve Soluble Fraction Ratio of α-Luffin Ribosome Inactivating Protein

Background

The increase of the protein expression via ribosomal manipulation is one of the suggested cellular mechanisms involved in EnBase fed-batch mode of cultivation. However, this system has not been implemented for cytotoxic proteins.

Objectives

Here, the expression pattern of α-Luffin, a ribosome inactivation protein (RIP) with an innate toxicity, was investigated in EnBase system and the effect of low temperature cultivation on the increase of α-Luffin solubility was determined.

Materials and Methods

The encoding cDNA for mature α-Luffin was synthesized and subcloned into pET28a plasmid under the control of T7 promoter. The E. coli expression yield in EnBase® Flo fed-batch system was compared with traditional batch mode at two temperatures: 25 °C and 30 °C. Sampling was performed at several time intervals and solubility of recombinant-protein was checked on SDS-PAGE in pellet and supernatant samples. The purification of recombinant protein was performed by Ni-NTA column.

Results

In fed-batch cultivation mode, the early incubation time was desirable at 30 °C whereas the maximum amount of soluble α-Luffin was achieved from the extended protein synthesis period (12 and 24h post induction) at 25 °C.

Conclusions

Our founding showed that EnBase had a greater efficacy in producing higher soluble protein ratios compared to batch cultivation growth rate, however for cytotoxic proteins, incubation temperature and time need to be optimized. Owing to the advantages of natural toxins from RIP family for producing anticancer immune-conjugates, well optimization of this protein expression is of importance regarding industrial aspects. The optimized condition proposed here is promising in terms of large scale soluble production of α-Luffin without the need for refolding.

Purification and functional characterization of recombinant balsamin, a ribosome-inactivating protein from Momordica balsamina

Balsamin, a type I ribosome-inactivating protein (RIP), has been shown to inhibit HIV-1 replication at the translation step. Our recent studies have shown that balsamin also possess anti-tumor, antibacterial and DNase-like activity, however, the amount of natural balsamin in Momordica balsamina seeds is limited and preclinical studies require large quantities of pure, bioactive balsamin. Therefore, in this study, we cloned the balsamin gene, expressed it in E.coli BL21 (DE3) strain and purified it by nickel affinity chromatography. Functional analysis indicated that balsamin exhibits both RNA N-glycosidase activity, releasing the Endo-fragment from rabbit reticulocyte rRNA, and DNase-like activity, converting the supercoiled form of a plasmid into the linear form in a concentration-dependent manner. Analysis of secondary structure revealed that recombinant balsamin mainly consisted of α-helical and random coiled with minimal turns and β-sheets. Recombinant balsamin was found to be stable in the temperature range of 20-60 °C and pH range of 6-9. Antimicrobial assays showed that the minimum inhibitory concentrations of recombinant balsamin for various pathogens ranged between 1.56 and 12.5 μg/ml. Heterologous expression and purification of balsamin carries great importance as it provides an alternative approach for large-scale preparation of biologically active recombinant balsamin, which is difficult from its natural source.

Cloning and soluble expression of mature α-luffin from Luffa cylindrica in E. coli using SUMO fusion protein

α-Lufin, found in Luaf cylindrica seeds, is a type I ribosome inactivating proteins. Cytotoxic effects make it an appropriate candidate for the construction of immunotoxins and conjugates. Because of limited natural resources, recombinant technology is the best approach to achieve large-scale production of plant-based proteins. In the present study, α-lufin protein was expressed in E. coli and the effects of different temperature conditions, SUMO fusion tag, and cultivation strategies on total expression and solubility were investigated. Protein expression was evaluated at different intervals (0, 4, 6, 8, 24 h) postinduction. Our results showed that EnBase had higher eficiency than LB, and maximum solubility and total protein expression were achieved 24 h after induction at 30 °C and 25 °C, respectively. It was shown that SUMO tag is an effective strategy to improve protein solubility.

Mature Luffa Leaves (Luffa cylindrica L.) as a Tool for Gene Expression Analysis by Agroinfiltration

We exploited the potential of cucurbits for ectopic gene expression. Agroinfiltration is a simple and commonly used method to obtain transient expression of foreign genes in plants. In contrast to in vitro transformation techniques, agroinfiltration can be used for genetic modification of mature plant tissues. Although the cucurbits are commonly used as model plants for molecular biology and biotechnology studies, to date there are no literature sources on the possibility of transient gene expression in mature cucurbit tissues. Our research has shown that mature leaves of Luffa cylindrica L. (luffa), in contrast to other cucurbit species, can be successfully transiently transformed with Agrobacterium tumefaciens. We efficiently transformed luffa leaves with a reporter gene encoding β-glucuronidase (GUS). The GUS activity in transiently transformed leaf tissues was detected within 24 h after the infiltration with bacteria. Additionally, we have shown that the activity of a transiently expressed the GUS gene can be monitored directly in the EDTA-exudates collected from the cut petioles of the agroinfiltrated leaves. The results suggest that luffa leaves can be useful as a plant expression system for studies of physiological and biochemical processes in cucurbits.

Ribosome-inactivating proteins (RIPs) and their important health promoting property

Ribosome-inactivating proteins (RIPs), widely present in plants, certain fungi and bacteria, can inhibit protein synthesis by removing one or more specific adenine residues from the large subunit of ribosomal RNAs (rRNAs).

Anti-tumor activities and apoptotic mechanism of ribosome-inactivating proteins

Ribosome-inactivating proteins (RIPs) belong to a family of enzymes that attack eukaryotic ribosomes and potently inhibit cellular protein synthesis. RIPs possess several biomedical properties, including anti-viral and anti-tumor activities. Multiple RIPs are known to inhibit tumor cell proliferation through inducing apoptosis in a variety of cancers, such as breast cancer, leukemia/lymphoma, and hepatoma. This review focuses on the anti-tumor activities of RIPs and their apoptotic effects through three closely related pathways: mitochondrial, death receptor, and endoplasmic reticulum pathways.

Ribosome-inactivating and related proteins

Ribosome-inactivating proteins (RIPs) are toxins that act as N-glycosidases (EC 3.2.2.22). They are mainly produced by plants and classified as type 1 RIPs and type 2 RIPs. There are also RIPs and RIP related proteins that cannot be grouped into the classical type 1 and type 2 RIPs because of their different sizes, structures or functions. In addition, there is still not a uniform nomenclature or classification existing for RIPs. In this review, we give the current status of all known plant RIPs and we make a suggestion about how to unify those RIPs and RIP related proteins that cannot be classified as type 1 or type 2 RIPs.

Luffa cylindrica suppresses development of Dermatophagoides farinae-induced atopic dermatitis-like skin lesions in Nc/Nga mice

CONTEXT

The fruit pulp of Luffa cylindrica Roemer (Cucurbitaceae) (LC) has been used to induce hemostasis, resolve phlegm and clear fever in traditional Korean medicine. However, the efficacy of LC has not been examined in atopic dermatitis (AD).

OBJECTIVE

A 70% ethanol extract of LC was evaluated to determine anti-inflammation and anti-AD effects in vitro and in vivo.

MATERIALS AND METHODS

The inhibitory effects of LC on the production of PGE2 and histamine were respectively measured in lipopolysaccharide-treated (1 μg/mL) RAW264.7 macrophages and phorbol-12 myristate 13-acetate (50 nM) and A23187 (1 µM)-stimulated HMC-1 mast cells. The production of AD-related chemokines (RANTES, TARC, and MDC) were evaluated in IFN-γ and TNF-α-stimulated (10 ng/mL, each) HaCaT keratinocytes. LC (10 mg/mouse/d) was topically applied to the dorsal skin and ears of Dermatophagoides farina (Pyroglyphidae)-sensitized Nc/Nga mice for 4 weeks.

RESULTS

The IC50 values of LC on PGE2 and histamine production were 16.89 and 139.9 μg/mL, individually. The production of TARC and RANTES were inhibited 20% and 12% by LC (50 μg/mL) in HaCaT cells, respectively (p < 0.05). In sensitized-NC/Nga mice, the plasma levels of IgE and histamine were suppressed 36% and 41% by LC, respectively (p < 0.05). LC also reduced hemorrhage, hypertrophy, and hyperkeratosis of the epidermis and infiltration of mast cells in the dorsal skin and ear.

DISCUSSION AND CONCLUSION

LC can inhibit AD-like skin lesions and reduce the generation of IgE via inhibition of the inflammatory responses. LC has potential as a therapeutic agent to treat allergic diseases, including AD.

Preparation and antitumor effect of a toxin-linked conjugate targeting vascular endothelial growth factor receptor and urokinase plasminogen activator

The aberrant signaling activation of vascular endothelial growth factor receptor (VEGFR) and urokinase plasminogen activator (uPA) is a common characteristic of many tumors, including lung cancer. Accordingly, VEGFR and uPA have emerged as attractive targets for tumor. KDR (Flk-1/VEGFR-2), a member of the VEGFR family, has been recognized as an important target for antiangiogenesis in tumor. In this study, a recombinant immunotoxin was produced to specifically target KDR-expressing tumor vascular endothelial cells and uPA-expressing tumor cells and mediate antitumor angiogenesis and antitumor effect. Based on its potent inhibitory effect on protein synthesis, Luffin-beta (Lβ) ribosome-inactivating protein was selected as part of a recombinant fusion protein, a single-chain variable fragment against KDR (KDRscFv)-uPA cleavage site (uPAcs)-Lβ-KDEL (named as KPLK). The KDRscFv-uPAcs-Lβ-KDEL (KPLK) contained a single-chain variable fragment (scFv) against KDR, uPAcs, Lβ, and the retention signal for endoplasmic reticulum proteins KDEL (Lys-Asp-Glu-Leu). The KPLK-expressing vector was expressed in Escherichia coli, and the KPLK protein was isolated with nickel affinity chromatography and gel filtration chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis test demonstrated KPLK was effectively expressed. Result of in vitro cell viability assay on non-small cell lung cancer (NSCLC) H460 cell line (uPA-positive cell) revealed that KPLK significantly inhibited cell proliferation, induced apoptosis, and accumulated cells in S and G2/M phases, but the normal cell line (human submandibular gland cell) was unaffected. These effects were enhanced when uPA was added to digest KPLK to release Lβ. For in vivo assay of KPLK, subcutaneous xenograft tumor model of nude mice were established with H460 cells. Growth of solid tumors was significantly inhibited in animals treated with KPLK up to 21 days, tumor weights were decreased, and the expression of angiogenesis marker CD31 was downregulated; meanwhile, the apoptosis-related protein casspase-3 was upregulated. These results suggested that the recombinant KPLK may have therapeutic applications on tumors, especially uPA-overexpressing ones.

Retinervus luffae fructus (RLF): a novel material for use in negative pressure wound therapy

OBJECTIVE

To describe a modified negative pressure wound therapy (NPWT) apparatus, made mainly of an environmentally-friendly material derived from the retinervus luffae fructus (RLF; or loofah) plant.

METHOD

We retrospectively reviewed the charts of patients with skin defects on their limbs who underwent treatment with the RLF-NPWT device from September 2012 to October 2012. The endpoint of the study was healing by secondary intention; the time (days) to endpoint was evaluated.

RESULTS

The RLF-NPWT device was used in 16 patients. The age of the patients ranged from 15-82 years, with a mean age of 43 ± 17 years. Six patients sustained crush injuries, nine patients had open limb injuries from motor vehicle accidents and a further patient had a diabetic foot ulcer. The mean time to healing was 8.5 ± 2.4 days. Following RLF-NPWT, fresh granulation tissue was observed in all wound beds, with no evidence of macroscopical necrosis. All 16 patients in the study achieved secondary healing.

CONCLUSION

The environmentally friendly RLF-NPWT apparatus is easy to use and able to provide continual negative pressure for optimal preparation of the wound bed. The cost-effectiveness of RLF-NPWT compared to standard NPWT requires further investigation.

DECLARATION OF INTEREST

There were no external sources of funding for this study. The authors have no conflicts of interest to declare.

Ribosome-inactivating proteins: from plant defense to tumor attack

Ribosome-inactivating proteins (RIPs) are EC3.2.32.22 N-glycosidases that recognize a universally conserved stem-loop structure in 23S/25S/28S rRNA, depurinating a single adenine (A4324 in rat) and irreversibly blocking protein translation, leading finally to cell death of intoxicated mammalian cells. Ricin, the plant RIP prototype that comprises a catalytic A subunit linked to a galactose-binding lectin B subunit to allow cell surface binding and toxin entry in most mammalian cells, shows a potency in the picomolar range. The most promising way to exploit plant RIPs as weapons against cancer cells is either by designing molecules in which the toxic domains are linked to selective tumor targeting domains or directly delivered as suicide genes for cancer gene therapy. Here, we will provide a comprehensive picture of plant RIPs and discuss successful designs and features of chimeric molecules having therapeutic potential.