Antitumor Effects Of Vitamin Research Articles

The protective role of vitamin d in nasopharyngeal carcinoma: insights from Mendelian randomization and meta-analysis

BackgroundIn recent years, the anti-tumor effects of vitamin D have garnered increasing attention. However, previous epidemiological studies on the relationship between vitamin D and nasopharyngeal carcinoma (NPC) have yielded inconsistent results. This study aims to further explore whether vitamin D helps reduce the risk of NPC through Mendelian randomization (MR) and meta-analysis.MethodsBased on the core assumption of MR study, instrumental variables (IVs) for vitamin D, serving as genetic proxies, were obtained from summary data of large genome-wide association study (GWAS). Inverse-variance weighted (IVW) was utilized as the primary MR analytical method to explore the causal relationship between vitamin D and NPC. Sensitivity analyses included heterogeneity testing and horizontal pleiotropy testing. To further validate the robustness of the result, meta-analysis was employed to obtain pooled effects from databases of different sources.ResultsIn the discovery cohort, the IVW result suggest that vitamin D is a potential protective factor against NPC (odds ratio (OR) = 0.35, 95% confidence interval (CI): 0.13–0.89, P = 0.028). The finding was further corroborated by two independent replication cohorts [OR = 0.32, 95% CI: 0.13–0.80, P = 0.018 (ukb-d-30890_irnt); OR = 0.34, 95% CI: 0.13–0.90, P = 0.029(ebi-a-GCST90025967)]. Subsequent meta-analysis indicated that vitamin D markedly reduces the risk of NPC (OR = 0.34, 95% CI: 0.19–0.58, P < 0.001). Multiple sensitivity analyses, including heterogeneity analysis and horizontal pleiotropy tests, did not reveal any significant findings (all P > 0.05).ConclusionThis study provides robust evidence that vitamin D significantly reduces the risk of NPC. Through MR and meta-analysis, we have demonstrated a protective role of vitamin D in NPC development. These findings suggest that maintaining adequate vitamin D levels may be a potential strategy for reducing NPC. Further research is warranted to confirm these results and explore the underlying mechanisms involved.

Role of Fe, Transferrin and Transferrin Receptor in Anti-Tumor Effect of Vitamin C.

Simple SummaryHigh-dose vitamin C (VC) inhibits cell proliferation in a variety of tumors, which is mediated by ROS. Iron is an important factor in the Fenton reaction, in which H2O2 reacts with ferrous iron to produce hydroxyl radicals, which may enhance the killing of tumor cells. In this study, we investigated the roles of iron level and the mainly pathway of iron uptake-TF/TFR system on VC-induced cytotoxicity. We conducted a preliminary evaluation of the potential value of 68Ga-citrate imaging in the anti-tumor therapy of VC combined with iron supplementation.High-dose vitamin C (VC) exhibits anti-tumor effects, and the cytotoxicity of VC is correlated with oxidative stress. However, iron, as a redox metal, plays an important effect in redox cycling and free radical formation in cells. This study addresses the role of iron ion in the cytotoxicity of VC. We found that iron supplementation increases the anti-tumor effect of VC, which was influenced by the cellular iron uptake pathway–transferrin (TF)/transferrin receptor (TFR) system. The TFR expression of tumors can be assessed by 68Ga-citrate PET imaging, and it would be helpful to screen out the tumor type which is more sensitive to VC combined with an iron supplementation treatment.

Anti-Tumor Effect of Vitamin D Combined with Calcium on Lung Cancer: A Systematic Review and Meta-Analysis

Although many studies have demonstrated the impact of vitamin D and calcium on lung cancer, it remains the discrepancy for the effect of vitamin D and calcium on lung cancer. In this study, we aimed to verify the roles of vitamin D and calcium in the incidence and prognosis of lung cancer. A systematic literature search was performed by February 29, 2020. The relative risks (RRs) and hazard ratio (HRs) were pooled to evaluate the risk for the incidence and mortality of lung cancer. A total of 58,625 lung cancer cases from 40 studies were included. The risk (RR: 0.915, 95% Cl: 0.849–0.986) and mortality (RR: 0.718, 95% Cl: 0.530–0.973) of lung cancer were significantly decreased due to high circulating 25(OH)D level. Although the separate intake of vitamin D (RR: 0.909, 95% Cl: 0.801–1.031) and calcium (RR: 0.890, 95% Cl: 0.741–1.070) did not exhibit a protective effect on lung cancer, the combination supplement of vitamin D and calcium significantly decreased the incidence of lung cancer (RR: 0.811, 95% Cl: 0.659–0.999). High level of serum 25(OH)D could play the preventive role in lung cancer. Furthermore, vitamin D could be supplemented together with calcium against lung cancer.

Abstract 367: The connection of vitamin D3 induced cytotoxicity with the vitamin D3 receptor

Abstract [Purpose] This study aims to evaluate the possible antitumor effect of vitamin D. Vitamin D is a group of lipophilic compounds comprising of vitamin D2 and vitamin D3. Vitamin D3 has been shown to play an important role in humans. It has been previously reported that the onset risk of malignant melanoma and leukemia can be decreased by maintaining high vitamin D3 levels in the body. In addition, the cytotoxic effect of vitamin D on breast cancer cells has also been shown. In this study, the relationship between the cytotoxicity of vitamin D3 and vitamin D3 receptor (VDR) expression on melanoma and leukemia cells was examined. [Method] B16F10 melanoma (B16F10) and P388 leukemia (P388) cells were used in this study. Western blot analysis was performed to determine VDR expression in each cell type. To evaluate cytotoxicity, B16F10 or P388 cells were seeded at 1×105 cells/mL, and calcitriol as vitamin D3 (range 9 ng/mL-90 μg/mL) was added at once. After two days, cytotoxicity was evaluated by colorimetric analysis using Cell Counting Kit-8. Additionally, the cytotoxicity of P388 cells was determined following the combined treatment of vitamin D3 and retinoic acid. [Results and Discussion] Western blot analysis revealed that both B16F10 and P388 cell types, expressed VDR with a higher expression in P388 cells. In P388 cells, there was a significant reduction in cell viability following vitamin D3 treatment, which decreased to 10% at 90 μg/mL. In contrast, the viability of B16F10 cells following vitamin D3 treatment only slightly decreased. Interestingly, these results suggest that the cytotoxicity of vitamin D3 correlates with VDR expression. VDR reportedly forms a heterodimer with the retinoid X receptor. However, the presence of retinoic acid did not alter vitamin D3 cytotoxicity. Therefore, it was considered that cytotoxicity induced by vitamin D3 was not connected with the formation of the VDR-retinoid X receptor heterodimer. In conclusion, there was a higher expression of VDR in P388 cells compared with B16F10 cells. This higher expression correlated with a higher level of vitamin D3 cytotoxicity, suggests an antitumor effect of vitamin D3. This study proposes the possibility of using vitamin D3 as a novel treatment for leukemia and other cancers. Citation Format: Takaya Hoshi, Yuta Abe, Ikumi Sugiyama, Yasuyuki Sadzuka. The connection of vitamin D3 induced cytotoxicity with the vitamin D3 receptor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 367.

Detection of subclinical vitamin K deficiency in neurosurgery with PIVKA-II

Vitamin K is known for supporting the carboxylation of hepatic coagulation proteins. Levels of proteins induced by vitamin K absence for factor II (PIVKA-II) reflect hypocarboxylated prothrombin and can be used to detect subclinical vitamin K deficiency. The aim of this study was to determine the prevalence of perioperative subclinical vitamin K deficiency among neurosurgical patients using PIVKA-II and investigate the existence of any correlation to standard coagulation assays. Also, the antitumor effects of vitamin K were reviewed. Thirty-five patients undergoing brain tumor resection were included. Blood samples were drawn preoperatively, at the end of surgery and in the morning after surgery. In addition to PIVKA-II, factor II and the Owren and Quick prothrombin times were analyzed. Seventeen of 35 patients had elevated PIVKA-II levels before surgery, which continued to be above normal range postoperatively. Median PIVKA-II and Owren prothrombin time (PT-INR) were increased on the morning day 1 postoperatively compared to before surgery, whereas Quick end-stage prothrombin time (EPT) decreased and factor II was unaffected. Postoperative complications were connected to high PIVKA-II increases. Positive correlations between PIVKA-II and factor II and body mass index (BMI) were found. In conclusion, PIVKA-II was increased in many patients preoperatively and then increased by the morning following surgery. Standard coagulation assays were largely non-pathological. Correlations were demonstrated between PIVKA-II and factor II and BMI. The effect of perioperative treatment with different vitamin K supplements should be investigated in future studies, as well as clinical trials evaluating their antitumor effects.

α-Tocopheryl Succinate Affects Malignant Cell Viability, Proliferation, and Differentiation.

The widespread occurrence of malignant tumors motivates great attention to finding and investigating effective new antitumor preparations. Such preparations include compounds of the vitamin E family. Among them, α-tocopheryl succinate (vitamin E succinate (VES)) has the most pronounced antitumor properties. In this review, various targets and mechanisms of the antitumor effect of vitamin E succinate are characterized. It has been shown that VES has multiple intracellular targets and effects, and as a result VES is able to induce apoptosis in tumor cells, inhibit their proliferation, induce differentiation, prevent metastasizing, and inhibit angiogenesis. However, VES has minimal effects on normal cells and tissues. Due to the variety of targets and selectivity of action, VES is a promising agent against malignant neoplasms. More detailed studies in this area can contribute to development of effective and safe chemotherapeutic preparations.

Assessment of vitamin D and VDR gene expression in colorectal cancer patients

Background: Vitamin D insufficiency may increase risk and/or progression of cancer. Vitamin D acts through a nuclear receptor (VDR) which binding to vitamin D response elements causes changes in many genes expression. The aim: to assess the serum concentration of 25-hydroxycholecalciferol (25(OH)D3) and tissue VDR expression in colorectal cancer patients in relation to disease stage, tumor localization and disease progression. Material &amp; Methods: The study group consisted of 39 patients with colorectal cancer (mean age 65,5±6,8 yrs, 23/16 male/female) and a control group consisted of 25 patients (mean age 51,0±6,9 yrs; 8/17 male/female) without gastrointestinal disease and without neoplasm. Serum level of 25(OH)D3 was measured by HPLC/UV. RNA was isolated from homogenized normal colonic mucosa and tumor tissue then RT-PCR was performed. Results: The mean serum concentration of 25(OH)D3 was lower in the colorectal cancer patients as compared to the control group. The difference was significantly lower only for the patients with the early stages of the disease (p&lt;0.02) and for the patients with tumor present in rectum (p&lt;0.03). Higher VDR expression in tumor tissue than in normal colonic mucosa was observed. For the patients with the early stages of the disease (stage A, B1, B2) higher expression of VDR as compared to the patients with advanced stages (stage C1, C2, D) was noticed. Moreover, VDR expression was higher in tumor tissue obtained from disease-free patients as compared to the patients with disease progression noted one-year-follow-up (p&lt;0.04). Conclusion: Antitumor effect of vitamin D depends on VDR expression in tumor tissue.

P0321 : Increased anti-tumor effect of vitamin D after CYP24A1 inhibition on HCC cell lines

P0320 TARGETING TGF-BETA I WITH THE TRANSFORMING GROWTH FACTOR RECEPTOR TYPE I KINASE INHIBITOR, LY2157299, MODULATES STEMNESS-RELATED BIOMARKERS IN HEPATOCELLULAR CARCINOMA B. Rani, F. Dituri, Y. Cao, U. Engstrom, L. Lupo, S. Dooley, A. Moustakas, G. Giannelli. Department of Biomedical Sciences and Human Oncology, University of Bari, Bari, Italy; Biomedical Center, Ludwig Institute for Cancer Research, Science for Life Laboratory, Uppsala, Sweden; Department of Emergency and Organ Transplantation, University of Bari, Bari, Italy; Molecular Hepatology-Alcohol associated diseases, Department of medicine II, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany; Department of Medical Biochemistry and Microbiology, and Ludwig Institute for Cancer Research, Science for Life Laboratory, Box 581 Biomedical Center, Uppsala, Sweden E-mail: bhavna.rani@uniba.it

Antitumor effects of vitamin D analogs on hamster and mouse melanoma cell lines in relation to melanin pigmentation.

Deregulated melanogenesis is involved in melanomagenesis and melanoma progression and resistance to therapy. Vitamin D analogs have anti-melanoma activity. While the hypercalcaemic effect of the active form of Vitamin D (1,25(OH)2D3) limits its therapeutic use, novel Vitamin D analogs with a modified side chain demonstrate low calcaemic activity. We therefore examined the effect of secosteroidal analogs, both classic (1,25(OH)2D3 and 25(OH)D3), and novel relatively non-calcemic ones (20(OH)D3, calcipotriol, 21(OH)pD, pD and 20(OH)pL), on proliferation, colony formation in monolayer and soft-agar, and mRNA and protein expression by melanoma cells. Murine B16-F10 and hamster Bomirski Ab cell lines were shown to be effective models to study how melanogenesis affects anti-melanoma treatment. Novel Vitamin D analogs with a short side-chain and lumisterol-like 20(OH)pL efficiently inhibited rodent melanoma growth. Moderate pigmentation sensitized rodent melanoma cells towards Vitamin D analogs, and altered expression of key genes involved in Vitamin D signaling, which was opposite to the effect on heavily pigmented cells. Interestingly, melanogenesis inhibited ligand-induced Vitamin D receptor translocation and ligand-induced expression of VDR and CYP24A1 genes. These findings indicate that melanogenesis can affect the anti-melanoma activity of Vitamin D analogs in a complex manner.

Vitamin d: are we ready to supplement for breast cancer prevention and treatment?

Vitamin D deficiency is a potentially modifiable risk factor that may be targeted for breast cancer prevention and treatment. Preclinical studies support various antitumor effects of vitamin D in breast cancer. Numerous observational studies have reported an inverse association between vitamin D status, including circulating 25-hydroxyvitamin D (25(OH)D) levels, and breast cancer risk. The relationship between vitamin D and mammographic density, a strong predictor of breast cancer risk, remains unclear. Studies analyzing the link between genetic polymorphisms in vitamin D pathway genes and breast cancer incidence and prognosis have yielded inconsistent results. Vitamin D deficiency among breast cancer patients has been associated with poorer clinical outcomes and increased mortality. Despite a number of clinical trials of vitamin D supplementation, the efficacy, optimal dosage of vitamin D, and target blood level of 25(OH)D for breast cancer prevention have yet to be determined. Even with substantial literature on vitamin D and breast cancer, future studies need to focus on gaining a better understanding of the biologic effects of vitamin D in breast tissue. Despite compelling data from experimental and observational studies, there is still insufficient data from clinical trials to make recommendations for vitamin D supplementation for breast cancer prevention or treatment.

Identification of microRNA-98 as a Therapeutic Target Inhibiting Prostate Cancer Growth and a Biomarker Induced by Vitamin D

The anti-tumor effect of vitamin D has been well recognized but its translational application is hindered by side effects induced by supra-physiological concentration of vitamin D required for cancer treatment. Thus, exploring the vitamin D tumor suppressive functional mechanism can facilitate improvement of its clinical application. We screened miRNA profiles in response to vitamin D and found that a tumor suppressive miRNA, miR-98, is transcriptionally induced by 1α,25-dihydroxyvitamin D(3) (1,25-VD) in LNCaP. Mechanistic dissection revealed that 1,25-VD-induced miR-98 is mediated through both a direct mechanism, enhancing the VDR binding response element in the promoter region of miR-98, and an indirect mechanism, down-regulating LIN-28 expression. Knockdown of miR-98 led to a reduction of 1,25-VD anti-growth effect and overexpression of miR-98 suppressed the LNCaP cells growth via inducing G2/M arrest. And CCNJ, a protein controlling cell mitosis, is down-regulated by miR-98 via targeting 3'-untranslated region of CCNJ. Interestingly, miR-98 levels in blood are increased upon 1,25-VD treatment in mice suggesting the biomarker potential of miR-98 in predicting 1,25-VD response. Together, the finding that growth inhibitive miR-98 is induced by 1,25-VD provides a potential therapeutic target for prostate cancer and a potential biomarker for 1,25-VD anti-tumor action.

Abstract 1606: Antitumor effects of vitamin D in a carcinogen-induced mouse model of lung cancer

Abstract Lung cancer accounts for the majority of cancer mortality in both men and women. It is critical to better understand the biology of lung cancer development as no preventive agents and few effective treatment options exist for lung cancer. Epidemiological studies indicate that low serum levels of 25(OH)D3 are associated with increased risk and poor prognosis of lung cancer. Calcitriol, the active metabolite of vitamin D, induces cell cycle arrest, apoptosis and differentiation in preclinical and clinical studies, has limited toxicity, and hence, is an attractive agent for chemoprevention. To investigate the preventive effects of vitamin D on lung squamous cell carcinoma (SCC), pre-clinical studies were conducted using a carcinogen-induced (CI) mouse model of lung SCC which uses N-nitroso-tris-chloroethylurea (NTCU) applied topically to the back of a SWR/J mouse twice weekly. Following ∼15 weeks of NTCU treatment, mice begin to develop bronchial epithelial hyperplasia and in time, progress through metaplasia, carcinoma in situ, and ultimately form lung SCC by approximately 35 to 40 weeks. We conducted a preliminary study investigating the effects of vitamin D on cancer progression in the CI model where animals received NTCU (80 mM/week). 12 week old female mice were randomized into one of three treatment groups: 1) vitamin D deficient diet (DD) (0IU D3 in the diet), 2) sufficient diet (SD) (2000IU/day D3 in the diet) and 3) SD with weekly intraperitoneal (IP) injections of calcitriol (80 ug/kg) (SD+D). Animals treated with NTCU on a DD, SD and SD+D had average serum 25(OH)D3 levels of 15, 70 and 75 nmol/L, respectively (normal range in mice is 70- 90 nmol/L). Preliminary histological evaluation at 12 weeks revealed bronchial epithelial hyperplasia in both the SD and SD+D groups. There were more advanced changes including hyperplasia, metaplasia and dysplasia in the DD mice. The histological evaluation of the DD mice at 24 weeks revealed even more advanced disease, in that most mice had developed lung SCC. The histological evaluation of the SD and SD+D groups at 24 weeks indicated the presence of bronchial epithelial hyperplasia, squamous metaplasia and dysplasia in all mice with some low level of carcinoma in situ. This study indicates that mice deficient in vitamin D develop disease at a more rapid rate suggesting that vitamin D status may play an important role in progression of lung SCC. Supported by NCCAM F31 AT006487 &amp; R01-CA-067267. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1606. doi:1538-7445.AM2012-1606

Vitamin D, vitamin D analogs (deltanoids) and prostate cancer

‘Vitamin D’ is a generic term for a family of secosteroids, members of which bind to the vitamin D receptor. Calcitriol, the active form of vitamin D, has antiproliferative effects on many tumor cells. However, clinical use of calcitriol in cancer prevention or therapy is limited because it induces hypercalcemia at the necessary supraphysiological doses. The anti-tumor effects of vitamin D analogs (deltanoids) have been researched extensively; more than 3000 deltanoids have now been described. Prostate cancer is more common in northern geographic regions; mortality decreases with exposure to sunlight. As UV light is necessary for vitamin D synthesis in the skin, it has long been dogma that vitamin D is involved. This review concerns deltanoids that have been assessed for use in treating or preventing prostate cancer.

Anti-tumor effect of vitamin A and D on head and neck squamous cell carcinoma

Objectives: Vitamin A and D 3 have a very strong differentiation induction effect. Study design: We examined the anti tumor effect on head and neck squamous cell carcinoma (HNSCC) by treatment with several vitamins having strong differentiation induction effects in vitro. Methods: We used KB cell that an oral floor squamous cell carcinoma, vitamins as all- trans retinoic acid (ATRA), 4-[3,5-bis (trimethylsilyl) benzamido] benzoic acid (TAC-101), 1α,25(OH) 2D 3 (calcitriol) and 22-oxa-1,25-(OH) 2D 3 (OCT). We determined receptors of vitamin A and D 3 using RT-PCR. Furthermore, we investigated the proliferation of tumor cells in concentration dependency using [ 3H]TdR uptake method, apoptosis and apoptosis related factors using TUNEL method and real-time PCR, cell cycle changes using flow cytometry, changing of the sensitivity of using MTT method, cytokine production and the angiogenesis factor using ELISA, by treatment with these vitamins. Results: The deficit of RAR-β was found in the KB cell. Each vitamin suppressed the cell proliferation, induced apoptosis, and cell cycle arrest, upregulated sensitivity of the chemotherapeutics drugs and downregulated several angiogenesis factors and an apoptotic factor; survivin. Conclusions: These results support the idea that vitamin A, D 3 and their derivatives are useful for preventing and/or treating patients with HNSCC.

Antitumor effects of vitamin A against Shope carcinoma cells

The antitumor effects of retinol were tested on three cell lines which were derived from a single Shope carcinoma and differed in their degree of differentiation. Addition of retinol to cultures induced growth retardation and morphological changes of these sublines. On removal of retinol from the culture medium, reversion of the undifferentiated subline was observed, but the two differentiated sublines did not revert. The tumorigenic potential of the differentiated sublines was lost or greatly reduced when they were injected into nude mice after 7 days of culture with retinol, whereas the potential of the undifferentiated subline was only slightly reduced. These results suggest that retinol may be effective against differentiated squamous cell carcinomas, but not against undifferentiated tumors.

Immunological role of vitamin A and its related substances in prevention of cancer.

The antitumor effects of vitamin A and its related substances, vitamin E, vitamin K, beta-carotene, ubiquinone, phytol, and squalene, were examined using a syngeneic murine tumor system. Intraperitoneal administration of these substances (0.19 mumol/mouse/day) slightly suppressed the growth of Meth A fibrosarcoma cells inoculated s.c. into Balb/c mice. Administration of all test substances except beta-carotene significantly suppressed the growth of Meth A fibrosarcoma cells rechallenged in Meth A-primed mice on day 10, but did not influence the growth of Meth 1 fibrosarcoma cells (another syngeneic tumor of Balb/c origin) rechallenged in Meth A-primed mice on day 10. The growth of Meth A tumor cells was suppressed when Meth A was inoculated together with lymph node cells obtained from the Meth A-primed Balb/c mice treated with vitamin A, vitamin E, phytol, or squalene. Our findings suggest that certain constituents in green-yellow vegetables may contribute to the prevention of cancer by augmenting an immunological response against tumor cells in the early stages of carcinogenesis.

Antitumor effects of vitamin A and inhibitors of ornithine decarboxylase in cultured neuroblastoma and glioma cells

The antiproliferative effects of vitamin A analogs and difluoromethyl ornithine, an irreversible inhibitor of ornithine decarboxylase, were evaluated in cultured neuroblastoma and glioma cells. Retinol and retinoic acid arrested the proliferation of neuroblastoma at concentrations of 50 μM; retinal was effective at 5 μM. Glioma cells were 5–10 fold less sensitive to all three analogs. A correlation existed between the inhibition of growth and the inhibition of ornithine decarboxylase in both cell lines treated with the retinoids. Difluoromethyl ornithine did not toally arrest tumor growth at concentrations of 5 mM; however, the antitumor effects were enhanced with the addition of retinol. An earlier and more complete cytostatic response was observed in glioma cells which had been treated with the combination of 100 μM retinol and 5 mM difluoromethyl ornithine than in cells which had been treated with either agent alone. These results show that tumors of neural origin are retinoid sensitive and suggest that a combination of vitamin A analogs and ornithine decarboxylase inhibitors may produce an increased chemotherapeutic response.

Hemmung von Tumorwachstum und Metastasen in Lewis-Lungentumor-tragenden Mäusen durch Vitamin A + BCG

The anti-tumor effect of vitamin A and/or BCG was investigated in Lewis lung tumor system. Tumor growth and lung metastases were significantly suppressed, when tumor cells were mixed with BCG and inoculated subcutaneously into vitamin A-treated animals. Survival time was also prolonged by the same treatment. Vitamin A alone, without BCG, showed no effect on tumor growth, lung metastases or survival time.

Suppressed Tumor Growth and Metastasis by Vitamin A + BCG in Lewis Lung Tumor Bearing Mice

The anti-tumor effect of vitamin A and/or BCG was investigated in Lewis lung tumor system. Tumor growth and lung metastases were significantly suppressed, when tumor cells were mixed with BCG and inoculated subcutaneously into vitamin A-treated animals. Survival time was also prolonged by the same treatment. Vitamin A alone, without BCG, showed no effect on tumour growth, lung metastases or survival time.