Keywords

3.1 Cancer: Role of Immune System

The human immune system is capable of specific obliteration of tumours without any toxicity to the normal tissues. In addition, the immune system can also preserve this memory for a long term and prevent the cancer reoccurrence via a process known as ‘immunosurveillance’. The research in the immuno-oncology field has presented us with concrete substantiation that immunosurveillance can not only identify tumours but also stop and prevent reoccurrence of the same for a long term (Finn 2012). The idea of immunosurveillance was accredited in the 1990s when research involving knockout mice animal models corroborated the reality of the concept of cancer immunosurveillance in spontaneous and chemically induced tumours. Since then the dominant roles of the effector cells of the immune system such as natural killer T cells, B cells, perforin and interferons (IFN) (I and II) were elucidated in cancer immunosurveillance (Dunn et al. 2002, 2005; Kim et al. 2007). The target specificity of the immune response exists in the differentiation ability of the antigens of the tumour. Other than these, the viral proteins in tumour instigated by viruses, the self-expressed proteins from the tumour surface, and the mutated and the non-mutated proteins from the onco genes exhibit virtuous targets for immunosurveillance (Finn 2012). The cancer immunoexpurgation resulting from immunosurveillance generally follows three essential phases, i.e., elimination, equilibrium and escape (Dunn et al. 2002). The cancer cells are initially eliminated by the effector cells such as natural killer cells and IFN-γ from the innate response of the immune system. Eliminating the transformed cells can result in decreased immunogenicity thereby rendering the tumour resistant to effector cells of the immune system in the equilibrium phase. Ultimately, during the progression of the tumour when diagnostic methods are able to detect the size of the tumour, factors such as tumour-derived soluble factors can instigate various mechanisms in the tumour microenvironment for the escape from the attack of the immune system (Kim et al. 2006).

In the recent years, research has proved the role of probiotics in exalting the immune response for the fight of cancer (De Leblanc et al. 2007). Many strains of probiotic organisms have the potential to impact innate mechanisms of defence such as phagocytosis (Schiffrin et al. 1995, 1997; Pelto et al. 1998; Arunachalam et al. 2000). Perdigon et al. in 1988 proved the potential of L. acidophilus and L. casei in systemic immunostimulation by the increase in the phagocytosis capability of murine peritoneal macrophages (Perdigon et al. 1988). Similarly, probiotic organisms also help in regulating the activity of natural killer cells (Gill et al. 2001), enterocytes and cytokines production (Lammers et al. 2002). Probiotics also impact the adaptive immunity by stimulating the production of IgA (Link-Amster et al. 1994; Fukushima et al. 1998; Isolauri et al. 2000; Park et al. 2002), dendritric cells (DCs) and Treg cells (Christensen et al. 2002; Braat et al. 2004). In this chapter, we shall discuss the potential and use of probiotics for improving the immune system in cancer condition.

3.2 Probiotics: Improving Immunity

Probiotics exert several beneficial effects on the host immune system. These effects include blocking pathogenic bacterial effects by producing bactericidal substances and competing with pathogens and toxins for adherence to the intestinal epithelium. Probiotics have been found to improve the innate as well as adaptive immunity by modulation of DCs, macrophages, and T and B lymphocytes functions via toll-like receptor-regulated signalling pathways. DCs being the antigen presenting cells play an important role in both adaptive and innate immunity. They also possess the properties of activating naïve T cells and have an important role in guiding the helper T cells towards the regulatory pattern or Th1 and Th2 (Lammers et al. 2002). The Th1 responses of the immune system decisively rely on the proficiency of the DCs to produce interleukin (IL)-12. The same are characterized by the production of IFN-γ and IL-2. The Th2 immune responses generally involve humoral immunity and IL-4, IL-5, IL-6 and IL-13 (Link-Amster et al. 1994; De Leblanc et al. 2007). Some of the prominently studied mechanisms of immunity involve the production of the IFN-α or induction of indoleamine 2,3-dioxygenase, an immunoregulatory enzyme with prime role in the interaction between the T cells and the DCs (Fukushima et al. 1998; Park et al. 2002).

In a recent study, it was demonstrated that probiotics activate the innate immunity and trigger the adaptive immune responses. It was found that a mixture of probiotics including strains of L. reuteri, L. acidophilus, B. bifidum, L. casei and Streptococcus thermophilus stimulated regulatory DCs expressing elevated levels of (Transforming growth factor beta) TGFβ, (cyclooxygenase-2) COX2, IL10 and IFN-α, thereby promoting the generation of forkhead family transcription factor (CD4+Foxp3+) regulatory T cells and increasing the suppressor activity. Additionally, the aforementioned probiotic mixture induced T and B cell hypo-responsiveness and down-regulated the T helper cells without induction of apoptosis. It was also revealed in the in vivo studies that the aforementioned mixture supressed the intestinal inflammation, which involved association of CD4+Foxp3+ Tregs, induced by 2,4,6-trinitrobenzenesulfonic acid (Yan and Polk 2011).

3.2.1 Need of Probiotics in Cancer Therapy

Cancer is a cellular disorder in which a defective apoptotic pathway triggers uncontrolled cell growth. Normally, the cells grow and re-divide via mitosis, having control on the G1 phase. The loss of control on the Go pathway results in the condition called malignancy (Hamada et al. 2001). The advancements in medical science resulted in the development of new synthetic drugs against cancer. However, they have numerous side effects. With the advancement in the field of nutraceutical foods and nano-pharmacology, the first of its kind novel functional food to heal cancer is no far from the reality (Cencic and Chingwaru 2010).

Probiotics provide vital nutrients that impart health benefits and thus act as functional foods for dealing with many gastrointestinal disorders, and even cancer. These are the class of microorganisms residing in the gastrointestinal tract and assisting the digestive and enzymatic function of the host (Ciorba et al. 2015). Humans receive IgA from the milk of the mother along with the inoculation cultures of the Lactobacillus (Soto et al. 2014). The journey of Lactobacillus is affected by the dysbiosis phenomenon between the pathogenic strains and probiotics microbial flora. It has been found that the concentration of these microbes falls in between the therapeutic window and has the potential to act as prophylactic and curative agents against different diseases of the host (Sandes et al. 2017).

3.2.1.1 Antioxidant Nature of the Probiotics for Prophylaxis Against Gastrointestinal Diseases and Cancer

Recently, it has been proven that these living non-pathogenic microbiota, after administration in appropriate doses act as antioxidant mediators thereby preventing and curing many diseases. They show different pharmacological and physiological activities that play a vital role in the human immune system (Wang et al. 2017). Chemicals released by the Lactobacillus strains e.g. SOD (superoxide dismutase) act as antioxidant mediators. These microbes also display the potential to chelate various metal ions during the digestion process e.g. Lactobacillus casei is proved to chelate Fe2+ or Cu2+, due to its antioxidant nature (Amaretti et al. 2013).

Many signalling mechanisms at the cellular/molecular level assisted by the probiotic microbes involve multistep complex pathways (Table 3.1); Kelch-like erythroid cell-derived protein with CNC homology [ECH]-associated protein 1 (Nrf2-Keap1) deals with the transcriptional responses via exogenous sensitization (Smith et al. 2016) while the nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) deals by excessive oxidative stress loading in host cells. The anabolic processes involved in the cell growth cycle and cell division are generally governed by (mitogen-activated protein kinase) MAPK. Whereas its subtypes, p38-MAPK and c-Jun N-terminal kinases (JNKs) are linked with the diverse stresses encountered by the cell affected by osmotic shock and irradiations. The following table provides the various signalling pathways associated with the probiotic microbes in different host cells (Mishra et al. 2015; Wang et al. 2017).

Table 3.1 Signalling pathway regulated by the probiotics in relation to antioxidant activities
Full size table

Probiotics show antioxidant activity by producing metabolites like folate and glutathione (GSH). The folate regulates the vital metabolism signalling pathways involved in DNA replication, methylation and maintenance of wear and tear of the host cells. Evidence-based studies have shown that Bifidobacteria induces the folate formation in animal models and human trials. Further investigations showed that the L. fermentum is capable of regulating the GSH system (Mikelsaar and Zilmer 2009; Wang et al. 2017). Thus, it can be concluded that probiotic treatments enhance the level of antioxidant metabolites.

Deficiency of vitamin B12 and folate promotes excessive oxidative stress in patients with type II diabetes. It has been shown that consumption of the yogurt, rich in Lactobacillus species, improves the level of the vitamin B12 along with the plasma folate relieving the oxidative damage in diabetes patients (Wang et al. 2017, Li et al. 2017a, p. 12). The detailed illustration of the antioxidant mechanism exhibited by the probiotics is given in Fig. 3.1.

Fig. 3.1
figure 1

Antioxidant activities exhibited by the probiotics involving various regulatory mechanisms

Full size image

3.2.1.2 Anticancer Nature of the Probiotics

Lactic acid bacteria also known as Lactobacillus are a genus from the probiotics group and are found to be useful in healing various common disorders and even cancer. The cancer healing abilities exhibited by the probiotics include various mechanisms, the most prominent being the suppression of cancer-causing mediators (Nami et al. 2014). This is regulated by preventing the carcinogenic metabolites from causing DNA alterations. Additionally, probiotics participate in the proper execution of the cell apoptosis, thereby preventing the cancer invasion by metastasis and growth of cancer stem cells (Motevaseli et al. 2017). The various mechanisms by which the probiotics act against cancer cells are illustrated in Fig. 3.2 and are discussed in detail in the following sections (Zhang et al. 2012; Yu and Li 2016; Motevaseli et al. 2017)

Fig. 3.2
figure 2

Probiotic mechanisms inhibiting the infestation of the cancer

Full size image
3.2.1.2.1 Protecting Host by Cell–Cell Adhesion

Normal physiology of the host tissue consists of tight junctions of the endothelial system showing cellular integrity. However, during the metastasis of cancer, these structures are weakened due to the damages in the scaffold proteins consisting of occludin and zonaoccludens-1 (ZO-1) (Motevaseli et al. 2017). Sometimes, the host cell membrane degrading agents such as matrix metalloproteinases assist the cancer cells to damage the structural integrity and invade other cellular structures and that is where probiotics play a role (Wan et al. 2014). The use of probiotics in a patient before surgery was found to enhance the liver barrier, thereby preventing the metastases (Eizaguirre et al. 2002; Dimitrov et al. 2014; Wang et al. 2017). Lactobacillus was found to be effective against cancer due to its cell adhesion mechanisms whereas L. rhamnosus decreased the overexpression of matrix metalloproteinase-2 in Caco2 cell line, thus maintaining cell–cell adhesion (Jan et al. 2002; von Ossowski et al. 2010; Motevaseli et al. 2017). Table 3.2 list cell–cell adhesion mechanism exhibited by probiotics.

Table 3.2 Cell–cell adhesion mechanism exhibited by the probiotics
Full size table
3.2.1.2.2 Protecting Host by Inhibiting the Epithelial-Mesenchymal Transition (EMT)

The host’s biological mechanism enables the epithelial cells to get polarized and develop affinity with the cell membrane. This results in the alteration of biochemical processes affecting the migratory dimensions of the host cell against the invasion of cancerous cell. CXCŘ4 gene is found to be effective in enhancing the signalling pathway of EMT resulting in metastasis (Chen et al. 2012). The CXCŘ4 antibodies inhibit the adhesion to the cancerous cells preventing their migration. L. acidophilus is found to down-regulate the expression of CXCR4 and inhibit colon cancer in mice models (Chen et al. 2012; Motevaseli et al. 2017, 2018). Table 3.3 lists EMT inhibition mechanism of the probiotics on the host cell.

Table 3.3 EMT inhibition mechanism of the probiotics on the host cells
Full size table
3.2.1.2.3 Inhibition of Tumour Microenvironment

The tumour microenvironment is developed by the communications that exist between the normal cells and tumour cells. The tumour-inducing cells in the microenvironment possess the ability to undergo various stages of tumour formation called tumourigenesis. These cells are non-malignant in nature and are related to the cells of the immune system and lymph nodal areas. A recent investigation carried out by the researchers demonstrated the anti-metastatic activities of Lactobacillus via alterations in the tumour microenvironment (Liu et al. 2015). Another study involving use of L. casei YIT018 in guinea pigs demonstrated their ability in suppressing the lymph node metastasis (Church and Galon 2015; Motevaseli et al. 2017). Table 3.4 lists mechanisms of tumour microenvironment inhibition by the proteins.

Table 3.4 Mechanisms of tumour microenvironment inhibition by the probiotics (Orlando et al. 2009; Church and Galon 2015; Motevaseli et al. 2017)
Full size table
3.2.1.2.4 Inhibition of the Cancer Stem Cells

In the recent studies, it has been demonstrated that the ‘cancer stem cells (CSC)’ play an important role in haematological malignancies. Similar to normal stem cells, these cells possess abilities like self-renewal and prolonged survival and contribute to cancer metastasis (Bui et al. 2015). These cells demonstrate heterogeneity in its functioning and show metastatic specificity to every organ system. The initiation and working of the CSC are due to the integral signalling pathways demonstrated by these cells against the host immune system (Llewellyn and Foey 2017). Alike stem cells, the self-transcriptional systems generated by CSC result in the induction of the hypoxic conditions in normal tissues. Further, this leads to regulations in signalling pathways involving multi-potent transcription factor Oct4, thereby initiating the migration of metastatic cells from one organ to the other. L. rhamnosus were observed to down-regulate the expression of hypoxia inducible factor-1α in breast cancer cell lines and colonic cancer cell lines (Bui et al. 2015; Motevaseli et al. 2017). Table 3.5 lists the pathways of cancer stem cell inhibition by the probiotics.

Table 3.5 Cancer stem cells inhibition by the probiotics (Saxami et al. 2016; Motevaseli et al. 2017)
Full size table

3.3 Probiotics and Cancer

The role of probiotics in cancer is recommended by several scientific indications and hypothesis that include upsurge in immune cell activation and suppression of the organisms converting procarcinogens. Below are some of the types of cancer and the study of probiotics associated with them.

3.3.1 Colon Cancer

Colorectal cancer is one of the leading cancers and nearly 862,000 deaths were reported in 2018 (Jan et al. 2002). The main reason behind the death owing to colorectal cancer is the leading dietary and behavioural risks taken by the patients which include obesity, low intake of fruits and vegetables, sluggish physical activity, alcohol and tobacco consumption, etc. (Holscher 2017). Along with the diagnosis, the prognosis of the cancer is a critical issue. To cope up with these problems, few synthetic medicines have been discovered after several years of clinical trials. However, many have been discarded in the last phase of trials owing to host–drug incompatibility issues. Systemic administration is preferred rather than local for the treatment of colorectal cancer. This results in systemic toxicity and adverse effects on vital organs. Hence, there is the need for a drug that can be delivered by per-oral route, having local action, minimizing the systemic toxicity, controlling morbidity and preventing the mortality (Ohkawara et al. 2007).

Many of the functional food and nutraceutical formulations are available commercially but are limited in curing minor diseases or disorders (Cencic and Chingwaru 2010; Patil et al. 2015, 2019a). In order to tackle this problem there is a need for novel nutraceutical formulations derived from natural origin (Patil et al. 2018, 2019b). These formulations should be able to control the manifestation of various types of cancer and the activity shall be consistent. Probiotic formulations are widely available in the market for the treatment of bowel disorders. Lactobacillus are generally derived and isolated from milk of different milking animals (Patil et al. 2019c). Furthermore, cultures of the Lactobacillus are also available as powder formulations possessing biological activities like mucoadhesion (Ouwehand et al. 2003) along with properties of hydrophobicity and autoaggregation. They also maintain proper bowel movements so as to prevent gastrointestinal tract disorders. Many reported functional foods have the ability to trigger and initiate the innate immune system of the host and biological properties, including antimicrobial properties, which combat the activities of pathogenic microorganisms (Campbell et al. 2000). The abilities possessed by some probiotic strains to scavenge the free radicals enable them as anticancer mediators. The prepared formulations are ideal if they mimic the natural antioxidant mediators having long shelf life. However, short shelf life of probiotics makes them less demanding in the existing market. Thus, the Lactobacillus formulations with longer shelf life along with the surplus biological activities like antimicrobial, antioxidant and anticancer activities can be beneficial. These microbes with antioxidant activity help in triggering the innate immunity system along with the release of certain chemicals (proteins) eventually killing the cancer cells. The preliminary investigation regarding the effect of probiotics is evaluated in cell line studies. The antiproliferative, antioxidant and anticancer nature of the probiotics have been demonstrated successfully on colonic cancer cell lines. The following Table 3.6 shows the anticancer model developed by using the different cell lines (Choi et al. 2006; Russo et al. 2007; Kim et al. 2008; Orlando et al. 2009, 2012; Motevaseli et al. 2013, 2017; Nami et al. 2014; Dimitrov et al. 2014; Ghoneum and Felo 2015; Yu and Li 2016; Saxami et al. 2016; Malik et al. 2018; Patil et al. 2020).

Table 3.6 In vitro cell line studies using different probiotics
Full size table

3.3.2 Cervical Cancer

Cervical cancer is another malignant form of cancer observed in women globally. Cervical cancer is ranked fourth in the major causes of cancerous death among women worldwide (Lv and Wang 2018). No signs or symptomatic conditions are observed among the patients with cervical cancer at early stages; however, it has been proven to be fatal at the later stages eventually leading to death (Musa et al. 2017). In general, the microecological environment of the vagina is very sensitive where minute chronic changes may precipitate cervical diseases. The current research has shown that certain microorganisms may alter the microecological environment of female genital tract resulting in the development of cervical cancer (Yang et al. 2018a). Infection by the human papillomavirus (HR-HPV) causes diseases like colitis, high-grade cervical intraepithelial neoplasia along with cervical diseases in women (Chase et al. 2015).

The vaginal microflora observed in the case of patients with cervical cancer showed different counts of pathogenic strains such as Staphylococcus epidermidis, Escherichia coli, Mycoplasma genitalium and Enterococci species as compared to the control (Yue et al. 2015; Grmek Košnik et al. 2016). However, the exact correlation between the different microflora in normal female genital tract and that of cervical cancer is not yet elucidated (Sierra et al. 2018).

Probiotics especially Lactobacillus have an important role in cervical disorders. The major potential mechanisms exhibited by the probiotics against cervical cancer include:

  1. (a)

    The autoaggregation mechanism that prevents adhesion of pathogenic strains to vaginal epithelial cells (VECs) inhibiting the conditions such as hyperplasia and wear–tear, thus decreasing the chances of any diseases or disorders.

  2. (b)

    The ability to produce organic acids, which maintain the acidic microenvironment of the vagina inhibiting the invasion and growth of pathogens (Medina-Colorado et al. 2017).

  3. (c)

    Release of chemicals such as bacteriocin, hydrogen peroxide and surface-active components, which play a vital role in inhibiting tumourigenic substances due to pathogens (Zadravec et al. 2015; Homburg et al. 2017).

  4. (d)

    An effective immune sensitizer, assisting the proliferation of B cells in the bone marrow (Yao et al. 2007; Lee et al. 2010).

Furthermore, Lactobacillus has been found effective in hampering the metabolic pathway of the cancerous cells by the release of nitric oxide (NO) (Sandes et al. 2017). Also they act as an effective humoral immunity modulator, which mediates the proliferation of T cells in the thymus gland of the infants (Sandes et al. 2017).

The preliminary investigation regarding the effect of probiotics is evaluated by cell line studies. The antiproliferative, antioxidant and anticancer nature of the probiotics has been demonstrated successfully on cervical cancer cell lines is presented in Table 3.7 (Ribelles et al. 2013; Nami et al. 2014; Kim et al. 2015; Motevaseli et al. 2016; Seo et al. 2016; Jang et al. 2017; Li et al. 2017b; Wang et al. 2018; Yang et al. 2018b).

Table 3.7 In vitro cell line studies using different probiotics
Full size table

3.4 Breast Cancer

The past few years have witnessed a reduction in mortality rate due to breast cancer. However, breast cancer still remains one of the common cancers prevalent among the female population of the world. The fraternity of science working in the area of breast cancer prophylaxis and therapy has thus started taking interest in the therapies other than chemotherapy for breast cancer. In vitro studies have demonstrated that breast cancer proliferation was inhibited by the use of isolated probiotics strains or supernatant from the cultures. It was also studied that heat killed cells, their cytoplasmic fractions and the live cultures namely Enterococcus faecalis and Staphylococcus hominis isolated from the breast milk caused cytotoxicity by means of apoptosis induction and arrest of the cell in the G0/G1 phase. It was also reported that the probiotics inhibiting the growth of the breast cancer also exhibited anti-inflammatory properties, suggesting their oncolytic property via immunomodulation (Han et al. 2015; Lee et al. 2015b; Nami et al. 2015; Hassan et al. 2016). The daily consumption of the strain Lactobacillus acidophilus was reported to increase the production of immunomodulatory cytokine IL12 in splenocyte culture. The same was stimulated by the tumour antigens in breast tumour bearing BALB/c mice (Yazdi et al. 2010).

3.5 Liver Cancer

The microbiome in the gut has been allied with the progression of liver disorders namely liver fibrosis (De Minicis et al. 2014), fatty liver disease (Raman et al. 2013; Wong et al. 2013) and in the recent years, liver cancer (Yoshimoto et al. 2013). In a recent study it was found that probiotics could inhibit the progression of the hepatocellular carcinoma in mice (Li et al. 2016). It was seen that upon feeding probiotics mixture to the mice with liver tumours, there was a shift in the gut microbiota, leading to the reduction of the tumour size in the liver of the mice. In addition to the above, it was also evident that there was a down-regulation in the angiogenic factors. Also, the level of the Th17 cells in gut and employment of Th17 to the tumour site were seen to be on the lower side in the mice treated with probiotics. The anticancer effect of the given probiotics was believed to have associated with the SCFAs-related pathway.

3.6 Other Cancers

Apart from the above-mentioned cancers, other types of cancers such as leukaemia, melanoma, lung cancer were also shown to have inhibited by the treatment of probiotics both in vivo and in vitro (Gui et al. 2015; Han et al. 2015; Lee et al. 2015a). Tuo et al. in their study demonstrated the antiproliferative activity of eight different strains of lactobacillus strains on leukaemia cells (Tuo et al. 2015). Similarly, Sivan et al. studied gut microbiota and immunotherapy on melanoma by the use of bifidobacterium species. It was found that the administration of the same caused reduction in the tumour volume of melanoma bearing mice (Sivan et al. 2015).

3.7 The Fate of Probiotics in the Animal and Clinical Studies

The anticancer effects of probiotics were determined by using various animal models such as rats and mice, the positive results of which lead to clinical trials on human volunteers (Fiala 1977; Chester et al. 1986; Foo et al. 2011; Asha and Gayathri 2012; Byelinska et al. 2015; El-Khadragy et al. 2018). Many studies were recently carried out using L. acidophilus, L. amylovorus, L. brevis, L. bulgaricus, L. casei immunitas, L. casei, L. crispatus, L. delbrueckii, L. fermentum, L. gallinarum, L. helveticus, L. johnsonii, L. johnsonii LC-1, L. lactis, L. plantarum, L. reuteri, L. rhamnosus, L. salivarius, L. sporogenes for analysing their anticancer activity using different animal models (Byelinska et al. 2015).

Mostly, probiotics have been employed as complementary synergistic mediators to manage intestinal disorders during chemotherapy and radiotherapy of cancer patients (Liu et al. 2011). L. casei DN-114001 was investigated for its progression in the host body by the stool consistency studies and bowel movements physiology in patients undergoing radiation (Merenstein et al. 2010). Many researchers reported that the combination of L. acidophilus and B. bifidum minimize radiation-induced diarrhoea (Hickson 2011). It has also been reported that chemotherapy changes the human gut microbiota inviting the pathogenic strains such as Clostridium difficile in the gut of the patients suffering from colorectal cancer (Nakanishi et al. 2003; Shinnoh et al. 2013). The enteral administration of bifidobacterium and Lactobacillus not only improved the patient’s intestinal environment but also minimized the side effects of radiotherapy (Walrand et al. 2012). Many studies showed that the administration of the probiotic formulations reduced post-operative trauma and intestinal infections (Liu et al. 2011; Zhang et al. 2012). Administration of probiotics also decreased the chances of tumour formations induced by aflatoxins, which are used as a marker for liver cancer (Kumar et al. 2012; Huang et al. 2017). The current research showed that the inclusion of probiotics as a nutraceutical agent reduces the risk of breast cancer in women after menopause. The consumption of these probiotics did not affect the level of the hormone in these women during their reproductive phase of the life (Bonorden et al. 2004). Probiotics were also found to be effective against the atypia form of colorectal tumours in patients consuming the L. casei for a period of 4 years (Gianotti 2010; Zhang et al. 2012).

3.8 Future Perspective and Conclusion

Cancer development is a progressive and protracted process involving complicated factors leading to metastasis. Epidemiological studies provide basis that probiotics have the potential to improve the lifestyle of the cancer patients and alter carcinogenesis. Research also shows that a number of probiotics have the potential of preventing cancer. These probiotics along with multiple health benefits possess anti-mutagenic and anti-carcinogenic properties. Such convincing research provides a strong basis for the acceptance of probiotics as chemo-supportive and chemo-preventive agents. However, the combination of the conventional treatment approaches and probiotics have been known to play a critical role in the variance of the clinical results in the trials. Owing to the promising results, the future of probiotics seems bright and probiotic therapy is now being preferred in cancer. The effectiveness however is dependent on the species and strain of probiotics exerting its actions via multiple pathways in cancer treatment/prevention. This opens several possibilities in the area of genetically modified/engineered probiotic strains. Research is being conducted on engineered strains of organisms not only for therapy but detection too and the results seem convincing. Undoubtedly, the research investigations in the field of probiotics for cancer is in its infancy; however, the same has reassuring future in preventive therapy.