Immunization with Human Papillomavirus 16 L1+E2 Chimeric Capsomers Elicits Cellular Immune Response and Antitumor Activity in a Mouse Model.

Development of cervical cancer is associated with persistent infections by high-risk human papillomavirus (HPV). Although current HPV L1-based prophylactic vaccines prevent infection, they do not help to eliminate prevalent infections or lesions. Our aims were (i) to generate a vaccine combining prophylactic and therapeutic properties by producing chimeric capsomers after fusion of the L1 protein to different fragments of E2 from HPV 16, and (ii) to evaluate their capacity to generate an antitumoral cellular response, while conserving L1 neutralizing epitopes. Chimeric proteins were produced in Escherichia coli and purified by glutathione S-transferase (GST)-affinity chromatography. Their structure was characterized using size exclusion chromatography, sucrose gradient centrifugation, electron microscopy, and anti-L1 enzyme-linked immunosorbent assay. All chimeric proteins form capsomers and heterogeneous aggregates. One, containing part of the carboxy-terminal domain of E2 and its hinge region (L1Δ+E2H/NC, aa 206-307), conserved the neutralizing epitope H16.V5. We then evaluated the capacity of this chimeric protein to induce a cytotoxic T-cell response against HPV 16 E2. In (51)Cr release cytotoxicity assays, splenocytes from C57BL/6 immunized mice recognized and lysed TC-1/E2 cells, which express and present endogenously processed E2 peptides. Moreover, this E2-specific cytotoxic response inhibited the growth of tumors of TC-1/E2 cells in mice. Finally, we identified an epitope (aa 292-301) of E2 involved in this cytotoxic response. We conclude that the L1Δ+E2H/NC chimeric protein produced in bacteria can be an effective and economically interesting candidate for a combined prophylactic and therapeutic vaccine that could help eliminating HPV16-positive low-grade cervical lesions and persistent viral infections, thus preventing the development of lesions and, at the same time, the establishment of new infections.

Kaempferitrin induces apoptosis via intrinsic pathway in HeLa cells and exerts antitumor effects.

ETHNOPHARMACOLOGICAL RELEVANCE: Justicia spicigera is used for the empirical treatment of cervical cancer in Mexico. Recently, we showed that Justicia spicigera extracts exerted cytotoxic and antitumoral effects and the major component of this extract was kaempferitrin (KM). MATERIALS AND METHODS: The cytotoxic and apoptotic effect of KM on human cancer cells and human nontumorigenic cells were evaluated using MTT and TUNEL assays, and Annexin V/Propidium iodide detection by flow cytometry. The effect of KM on cell cycle was analyzed by flow cytometry with propidium iodide. The apoptotic and cell cycle effects were also evaluated by western blot analysis. Also, different doses of KM were injected intraperitoneally daily into athymic mice bearing tumors of HeLa cells during 32 days. The growth and weight of tumors were measured. RESULTS: KM induces high cytotoxic effects in vitro and in vivo against HeLa cells. The general mechanisms by which KM induces cytotoxic effects include: cell cycle arrest in G1 phase and apoptosis via intrinsic pathway in a caspase dependent pathway. Also, KM exerts chemopreventive and antitumor effects. CONCLUSION: KM exerts cytotoxic and antitumor effects against HeLa cells.

The antitumoral effect of the American mistletoe Phoradendron serotinum (Raf.) M.C. Johnst. (Viscaceae) is associated with the release of immunity-related cytokines.

ETHNOPHARMACOLOGICAL RELEVANCE: Phoradendron serotinum is commonly used in Mexican traditional medicine for the empirical treatment of cancer. However, there are no studies regarding the antitumoral or immunomodulatory activities of Phoradendron serotinum. MATERIALS AND METHODS: The in vivo toxicity of ethanolic extracts of Phoradendron serotinum (PSE) was evaluated in mice according to the Lorke procedure. The in vitro immunomodulatory effects of PSE were evaluated estimating the effects of PSE on the pinocytosis, NO production and lysosomal enzyme activity in murine macrophages RAW 264.7. The effects of PSE on the proliferation of murine splenocytes and NK cell activity were also assayed. The cytotoxic effects on TC-1 (lung murine cancer cells) were evaluated using the MTT assay, whereas the apoptotic effect of PSE on TC-1 cells was evaluated using TUNEL assay. Also, different doses of PSE were injected intraperitoneally daily into C57BL/6 mice bearing tumors of TC-1 cells during 25 days. The growth and weight of tumors was measured. In addition, the levels of IL-2, IL-6, IL-12, IL-23 and IFN-γ in murine serum and supernatants of K562 cell-murine splenocyte cocultures were measured. RESULTS: PSE stimulated the proliferation, pinocytosis and lysosomal enzyme activity in murine macrophages with a similar potency than lypopolisaccharides 1 µg/ml. In addition, PSE stimulated the proliferation of murine splenocytes and induced the NK cell activity. PSE showed cytotoxic (IC(50)=1.9 µg/ml) and apoptotic effects against TC-1 cells. The LD(50) was 125 mg/kg by intraperitoneal route (i.p.) and 375 mg/kg by oral route. PSE administrated at 1, 5 and 10 mg/kg i.p. inhibited the tumor growth by 18%, 40% and 69%, respectively, in mice bearing TC-1 tumor. PSE increased the in vitro and in vivo release of IL-2, IL-6 and IFN-γ but lacked effect on IL-12 and IL-23 release. CONCLUSIONS: Phoradendron serotinum shows moderate toxic effects in vivo, exerts cytotoxic and apoptotic effects on TC-1 cells. Phoradendron serotinum also has antitumor effects in mice bearing TC-1 tumor and induces immunomodulatory activities in vivo. The results suggest that antitumoral effects of PSE are related with the production of immunity-related cytokines.

Antitumor and immunomodulatory effects of Justicia spicigera Schltdl (Acanthaceae).

ETHNOPHARMACOLOGICAL RELEVANCE: Medicinal plants are an important source of antitumor compounds. This study evaluated the acute toxicity in vitro and in vivo, as well as the cytotoxic, antitumor and immunomodulatory effects of ethanolic extracts of Justicia spicigera leaves (JSE). MATERIALS AND METHODS: The in vitro and in vivo toxicity of JSE was evaluated with comet assay in peripheral blood mononuclear cells (PBMC) and acute toxicity in mice, according to the Lorke procedure, respectively. The apoptotic effect of JSE on human cancer cells and human noncancerous cells was evaluated using flow cytometry with annexin-Alexa 488/propidium iodide. Also, different doses of JSE were injected intraperitoneally daily into athymic mice bearing tumors of HeLa cells during 18 days. The growth and weight of tumors were measured. The in vitro immunomodulatory effects of JSE were evaluated estimating the effects of JSE on the phagocytosis of the yeast Saccharomyces cerevisiae, NO production and H(2)O(2) release in macrophages, as well as the proliferation of splenocytes and NK activity. RESULTS: The comet assay showed that only JSE tested at 200 and 1000 µg/ml induced a significantly DNA damage in PBMC, compared to untreated cells, whereas the LD(50) was >5000 mg/kg by intraperitoneal route (i.p.) and by oral route. JSE showed pro-apoptotic (Annexin/PI) effects by 35% against HeLa cells, but lack toxic effects against human normal cells. JSE administrated at 10, 50 and 100 mg/kg i.p. inhibited the tumor growth by 28%, 41% and 53%, respectively, in mice bearing HeLa tumor. JSE stimulated, in a concentration dependent manner, the phagocytosis of Saccharomyces cerevisiae yeasts, the NO production and H(2)O(2) release by human differentiated macrophages. In addition, JSE stimulated the proliferation of murine splenocytes and induced the NK cell activity. CONCLUSION: Justicia spicigera shows low toxic effects in vitro and in vivo, exerts apoptotic effects on HeLa cells, has antitumor effects in mice bearing HeLa tumor and induces immunomodulatory activities in vitro.

Antitumor effect of Croton lechleri Mull. Arg. (Euphorbiaceae).

UNLABELLED: ETHNOPHARMAGOLOGICAL RELEVANCE: Medicinal plants are an important source of antitumor compounds. This study evaluated the acute toxicity in mice, as well as the cytotoxic and antitumoral effects of methanolic extracts of Croton lechleri leaves (CLE). MATERIALS AND METHODS: The cytotoxicity of CLE on human cancer cell lines and human non-cancerous cells was evaluated using the MTT and apoptosis assays. Apoptosis induced by CLE on human cancer cell lines was determined using flow cytometry with annexin-Alexa 488/propidium iodide. The acute toxicity in mice was performed according to the Lorke procedure. Different doses of CLE were injected intraperitoneally daily into athymic mice bearing tumor during 18 days. The growth and weight of tumors was measured. RESULTS: CLE showed low IC(50) values on HeLa (17µg/ml) cells but lack toxic effects against human normal cells. Induction of cell death in HeLa cells by CLE was confirmed by an increase of apoptosis (Annexin/PI) by 30% compared to untreated cells. The LD(50) was 356mg/kg by intraperitoneal route (i.p.) and 500mg/kg by oral route. CLE administrated at 1, 10 and 50mg/kg i.p. inhibited the tumor growth by 38%, 48% and 59%, respectively, in mice bearing HeLa tumor. CONCLUSION: Croton lechleri shows moderate toxic effects in vivo, exerts cytotoxic effects on HeLa cells and has antitumor effects in mice bearing HeLa tumor.

Advantages and disadvantages of current prophylactic vaccines against HPV.

Persistent infections with human papillomavirus (HPV) types of the alpha-papillomavirus genus that form the so-called high-risk (HR) group constitute the major risk for developing cancer of the uterine cervix, with nearly 500,000 new cases every year worldwide and approximately 250,000 deaths. Infections with low-risk (LR) types are usually associated with development of genital warts. Asymptomatic infections with both HR and LR types constitute the leading sexually transmitted disease, with approximately 8-12% of all sexually active women infected at a given time. Two commercial vaccines against HPV (Gardasil and Cervarix) are currently in the market in many countries worldwide. Both are produced with recombinant technologies, consist of self-assembled virus-like particles, the so-called VLPs, and have shown high immunogenicity. More important, they have been found to be highly efficient in preventing persistent infections and lesions not only from the uterine cervix, but also from the anus, vagina, and vulva. Unfortunately, vaccines are very expensive and unaffordable for many public health initiatives in developing countries. They include two types involved in cancer development (types 16 and 18); therefore, we can only expect a partial protection against cancer (70/100), making it necessary to implement novel strategies to detect precursor lesions and cancer in the postvaccine era. Strategies that include education and organized screening programs with detection of persistent infections should be implemented in developing countries if a reduction of cancer of the uterine cervix is expected over the next years.