Aloe Vera and its effects on cancer

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Abstract​

Many years ago, Aloe Vera was cited to have a lot of therapeutic properties including; anti-microbial, anti-viral, anti-cancer, anti-oxidant, anti-inflammatory, skin protection, wound healing, and regulation of blood glucose and cholesterol. However, Aloe could present some side effects. This review focused on the latest discoveries regarding the therapeutic role of Aloe plant or its compounds on the acquired biological capabilities for tumour growth and progression namely; evading growth suppressor, avoiding immune destruction, enabling replicative immortality, tumour promoting inflammation, activating invasion and metastasis, inducing angiogenesis, genome instability and mutation, resisting cell death, deregulating cellular energetics and sustaining proliferating signalling. It clarified the anti-cancer activities it exerts on different types of cancer and also highlighted some pro-oncogenic pathways that can be disrupted by different compounds of Aloe.

 

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BACKGROUND​

Around 420 species of Aloe are inventoried worldwide, but the most popular and widely used is Aloe Barbadensis Miller (also called Aloe Vera Linne, commonly referred to as Aloe Vera).1,2 For many years, Aloe is known to have many therapeutic properties which include; anti-microbial, anti-viral, anti-cancer, anti-oxidant, anti-inflammatory, skin protection, wound healing, and regulation of blood glucose and cholesterol.3

Several studies have illustrated the role of Aloe in cancer prevention and treatment, around 75 active compounds could potentially be of therapeutic value in cancer treatment.4 Even though Aloe or its compounds is known play anti-cancer activities in many cancer types in vitro, few studies have reported this evidence. Furthermore, many in vitro studies have demonstrated the effectiveness of the whole Aloe or its compounds in inhibiting the proliferation or growth of tumours.

Whole Aloe could have an inherent anti-tumour activity because of its many compounds and could be involved in the disrupting of tumour growth and progression signalling pathways. This mechanism of action could invariably inhibit the growth of cancer cells and lead to good prognosis. However, there are some controversies about toxicities of Aloe given the recent review which reported the side effects of Aloe especially for Aloe Vera on neoplastic and non-neoplastic cells.1

Many acquired capabilities are necessary for tumour growth and progression, namely; Evading growth suppressor, Avoiding immune destruction, enabling replicative immortality, tumour promoting inflammation, activating invasion and metastasis, inducing angiogenesis, genome instability and mutation, resisting cell death, deregulating cellular energetics and sustaining proliferating signalling.5 In its anti-cancer activities, the aloe could act on one or more of these capabilities for tumour growth and progression.

Therefore, this narrative literature review aimed to present the effectiveness of Aloe or its compounds on cancers taking into account the acquired capabilities of Cancer.

 

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Identification of Relevant Studies and Research Method​

We systematically searched on PubMed and google scholar databases. The combination of key words were Aloe and cancers, Aloe and tumours, Aloe and tumours suppressors, Aloe and cancer cytotoxicity, Aloe and cancer apoptosis, Aloe and tumour growth, Aloe and tumour proliferation, Aloe and tumour inflammation, Aloe and tumour and immune, Aloe and cancer metastasis, Aloe and cancer angiogenesis, Aloe and DNA cancer cells, Aloe and normal cells.

Through identified studies, we systematically identified any compound of Aloe which has any anticancer activity. To perform deeply our research, every time the item Aloe was replaced by the identified compound in the above combination. Other studies were identified through references.

 

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The Biological Capabilities of Cancer and Aloe​

Antigrowth activity of Aloe on cancer cells​

Aloe Vera proved its anticancer effect when it was administrated to rats with pleural tumour from hepatoma cells.6 The dichloromethane (CH2Cl2) extract of cape aloe (concentrated and dried leaves of various species of Aloe, mainly Aloe ferox) caused growth inhibitory effect in Ehrlich ascites tumour cells, a decrease in DNA synthesis and an accumulation of cells in the G1 phase.7

Cytotoxicity of Aloe on cancer cells​

The Aloin is a natural anthracycline and it is known that anthracycline class medication such as doxorubicin is used in treatment of various types of cancer namely breast carcinoma, osteosarcoma and cancer of soft tissues, Hodgkin lymphoma, non-Hodgkin lymphoma, Solid tumour of children, lung cancers, acute and chronic leukaemia, bladder cancer, ovarian cancer and gastric cancer.8,9 Aloin's cytotoxicity effect was found and more marked in breast cancer cells without ErbB-2 than those with ErbB-2.8 The Emodin, a natural anthraquinone found in Aloe10,11 and in other plants was involved in a cytotoxic activities in human myeloma.12

Apoptosis and antiproliferative activities of Aloe​

When murine myeloma cells were treated by leaf extract of Aloe arborescens, the antiproliferative activity was very high while in the control group of cells, the reverse activity was observed.13 Moreover, the anti-proliferative effect of total extract from leaves of Aloe arborescens (8%) was very high than the one of Aloe-emodin (natural hydroxyanthraquinone present in the leaves of Aloe Vera) in glioblastoma cells.14
Aloe-emodin showed its efficacy to inhibit proliferation and to induce apoptosis in many types of cancerous cells by various mechanisms (Table 1). They include human colon carcinoma cells, human oral squamous cell carcinoma, human gastric carcinoma cells, human colorectal cancer cells, human cervical cancer cells, human lung squamous carcinoma, human malignant glioma cells, human tongue squamous cancer cells, prostate cancer cells, human colon cancer cells, human nasopharyngeal carcinoma cells, human bladder cancer cells, and hepatocellular carcinoma cells.15–30

 

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