Since 2012, cancer is classified as the second major death cause in different regions of the world with an estimated number of 14.1 million new cases and 8.2 million deaths and expected to increase up to 21 million cases with 13.2 million causalities by 2030. Cancer is caused by a progressive aggregation of mutations in the genetic material of cell. Uncontrolled proliferation of cells, insensibility of growth factors, and capacity to infect surrounding tissues are the general characteristic of malignant tumours observed in most cancer patient. Only 5-10% of all cancer cases can be attributed to genetic defects, while 90-95% of the cases are related to external factors. According to the World Cancer Report (2014), around one-third of all deaths caused by cancer are resulting from high body mass, low fruits and vegetable intake, sedentary lifestyle, tobacco intake and alcohol ingestion [1].

Cancer cells have characteristics of genetic instabilities and accumulate somatic mutations rapidly [2-4]. There are various types of mutations such as point mutations, insertion/deletions, gene amplification and translocations in cancer cells. Some of them may lead to non synonymous somatic mutations altering the amino acid coding sequences and creating uncontrollable and abnormal proteins to promote cell proliferation [5]. Tumour-specific antigens (TSAs) called as neoantigens are created by genomic codon alterations, editing, usage, antigen processing and presentation [6, 7]. With the development of technologies of next generation sequencing (NGS), it becomes apparent that human cancers are very complex, bearing thousands of mutations [8]. Lactic acid bacteria including the genus Lactobacillus and Bifidobacterium have been shown to exert beneficial effects in humans. Purified Bifidobacterium has cell wall anti tumor activites and induces acvtivation of phagocytes to destroy growing tumor cells. Therefore resuming the equilibrium using the beneficial bacteria (called probiotics) for disease treatment and prevention has been regarded profitable[9].

Tumour microenvironment is constructed via the interactions between tumoral and non transformed cells. The latter have an active and often tumour-promoting role at all stages of tumorigenesis. The major non malignant cell types that are detected in this environment are the cells of immune system, the tumour vasculature and lymphatic’s, as well as the fibroblasts, pericytes and adipocytes [10]. The presence of a fraction of multipotent” cancer stem cells (CSC)” in solid tumours as well as haematological malignancies has resulted in suggestion of a new model foe explanation of tumorigenesis process ⁽¹¹⁾. Probiotics have been shown to influence all cell types and pathways implicated in the metastasis[12]. Vaccine can induce antitumor immune response in humans with cancer [13]. A large number of antigens cause genetic damage and include neoplastic transformation of cells; these agents are termed as carcinogens. Carcinogens can be chemical, radiation/ionization, microbiological.

More than 80% of patients suffering from cancer use vitamin, minerals, herbs, and other supplements include probiotics during the course of their disease [14]. Most probiotics are safe. However, care should be taken when administering probiotics to severely ill or immune compromised patients. There have been rare incidents of sepsis, endocarditis and liver abscess during the use of Lactobacillus; additionally, fungemia has been reported with use of S.boulardii, primarily in patients with sever comorbidities [15, 16]. The most common side effects of probiotics are constipation, flatulence, hiccups, nausea, infection and rash [17]. Supplemental intake might change the metabolism of anticancer drugs and consequently affect the outcome of therapy. Moreover besides the beneficial effects associated with probiotic administration, there could be several adverse events, including potentially life-threatening conditions because of immunosuppression in cancer patients undergoing chemotherapy. As many as 50% or more of the patients with cancer take vitamins, herbal preparations and other supplements, including probiotics without medical guidance [18].

Probiotics, the beneficial bacteria commonly found in yogurt cultures, are popularly thought as an aid for good digestion. But scientists are discovering that probiotics and the resulting healthy balance of gut bacteria confer a board spectrum of health benefits ⁽¹⁹⁾. Evidence demonstrates that supplementing with the right mix of probiotic bacteria such as Lactobacillus and Bifidobacterium species can powerfully ward off many of the factors leading to chronic disease. Probiotics can restore your body`s natural, intestine-based protection against a host of non-intestinal diseases and shield you from the diseases of aging [20]. Scientific studies have found associations between different species of Lactobacillus (Lactobacillus acidophilus, Lactobacillus paracasei, and Lactobacillus rhamnosus) and increased HDL cholesterol, balanced immune response and reduced markers of inflammation [21]. Similarly, associations have been found between Bifido bacterium species (Bifidobacterium lactis, Bifidobacterium bifidum and Bifidobacterium longum) and improved blood sugar control, decreased liver inflammation, and reduced DNA damage that could trigger malignant cell development, respectively [22, 23].

Probotics help your immune system at its best so it can detect and kill cells that can become cancer. Much of the probiotics research focuses on colon cancer, because most microorganisms live in our intestinal gut. Bacillus species exerts an anti cancer effect on human colon cancer cells stimulating Ig G production and modulates the number of CD4p, CD8p or Nk cells. In a recent study, daily consumption of probiotics for 6 months enhanced the clearence of human papillomavirus HPV which is known to be culprit of cervical cancer.

In recent years, reports have shown that dietary probiotics such as kefir have a great potential for cancer prevention and treatment. Kefir is fermented milk with Caucasian of Tibet origin, made from the incubation of kefir grains with raw milk or water. Kefir grains are a mixture of yeast and bacteria, living in a symbiotic association. Antibacterial, antifungal, anti-allergic and anti-inflammatory effects are some of the health beneficial properties of kefir grains. Furthermore, it is suggested that some of the bioactive compounds of kefir such as polysaccharides and peptides have great potential for inhibition of proliferation and induction of apoptosis in tumor cells. Many studies revealed that kefir acts on different cancers such as colorectal cancer, malignant T lymphocytes, Breast cancer and lung carcinoma.

Considerably, cell free supernants (CFS) from L.casei and L.rhamnosus have been shown to prevent colon cancer cell invasion suggesting that probiotics CFS has anti-metastatic bioactive substances that may participate in cell invasion decrease in vitro [24, 25]. Epithelial mesenchymal transition is a biological process that permits a polarized epithelial cell, which typically interacts with basement membrane through its basal surface, to undertake numerous biochemical alterations which result in acquisition of mesenchymal cell phenotype.