BACTERIA IN CANCER THERAPY

Presented by – GAURAV GANGWAR

INTRODUCTION • Therapies like photodynamic therapy,

HAMLET(human alpha-lactalbumin made lethal to tumor cell), gene therapy, complementary and alternative therapy etc. are intended or claimed to treat cancer.

• But a Live, attenuated, genetically modified, non-pathogenic bacterial species and bacterial spores are also capable of inhibiting the growth of cancer.

• The most potential and promising strategy is bacteria based gene-directed enzyme prodrug therapy.

HISTORY • Observation of German physicians W. busch &

F. fehleisen..• American physician William coley. ‘coley’s toxins’ – Two heat killed bacterial

species, Salmonella pyogenes and serratia marcescens.

BACTERIAL TARGET OF TUMOR• Obligate anaerobes (e.g Clostridium and

bifidobacterium) - target the anoxic area of tumor, and inhibit

the growth of tumor.• Facultative anaerobes (e.g. Salmonella and

Escherichia)• - identify and penetrate tumors by detecting

and chemotaxising towards small molecule gradients of serine, aspartate and ribose.

BACTERIA AS TUMORICIDAL AGENT• Clostridium novyi–NT (attenuated clostridium strain) produce toxicity

in tumor even after deletion of genes coding for a lethal toxin.• COBALT(combination bacteriolytic therapy)- Clostridium novyi-NT

spores were administered in combination with conventional chemotherapeutic agents like dolastatin-10, mitomycin C, vinorelbine and docetaxel.

• Bacillus Calmette Guerin(BCG),the most successful bacterial agent so far is used specifically for the treatment of superficial bladder cancer

• Salmonella strain VNP20009-after deletion of two genes msb & purl results in its complete attenuation.

-VNP20009 has been successfully investigated in phase 1 clinical trials in cancer patients.

BACTERIA AS VECTOR FOR GENE THERAPY AND TUMORICIDAL AGENT

• For delivering anticancer agents, cytotoxic peptides, therapeutics protein or produrg converting enzymes.

e.g. Salmonella • Two reports showed that when transfer of anti-

angiogenic genes (thrombospondin and endostain) from salmonella, prevent the formations of new blood vessel and stopped the nutrient supply in tumor cell.

• Attenuated selmonella typhimurium- used to deliver cytokines(IL-2) locally to liver cancer.

• Various therapeutic proteins, including TNF-alpha and platelet factor 4 fragment, have been cloned and expressed in VNP20009.

• Bifidobacterium adolescentis spore administration via tail vein of tumor-bearing mice resulted in strong inhibition of angiogenesis.

• Functional TNF- alpha has been cloned and expressed in C. acetobutylicum.

BACTERIA DIRECTED ENZYME PRODURG THERAPY

• Cytosine deaminase (CD) have been successfully expressed in C. sporogenes and C. acetobutylicum.

-convert 5-fluorocytosine(5FC) to 5-fluorouracil(5FC).• Salmonella vector has also been combined with CD and

nitroreductase, and success has been observed in vivo and it is currently undergoing in phase 1 clinical trials.

• TAPET(Tumor Amplified Protein Expression Therapy) uses VNP20009 expresses an E.coli CD for preferentially delivering anti-cancer drug to solid tumor.

• Salmonella + carboxypeptidase G2(enzyme convert mustard prodrug to DNA cross-linking agent) show significant results in vivo.

BACTERIAL TOXINS FOR CANCER• Cyclomodulins- bacterial toxins that subvert the host eukaryotic cell

cycle. E.g. 1. CNF(from E.coli) –cytotoxic necrosis factors, a cell-cycle

stimulator. - triggers the G1 - S transition and induces DNA replication.

2. CDTs (cytolethal distending toxins) found in several Gram- negative bacteria,

-cell-cycle inhibitor

3.Cif from enteropathogenic and enteroheamorrhagic E.coli, - block mitosis and inhibit clonal expansion of

lymphocytes.

-Bacterial toxins binding to surface antigens

• Pseudomonas exotoxin A inhibit protein synthesis by catalytically ribosylate EF-2.

• Clostridium perfringens enterotoxic (CPE) investigated for colon, breast, and gastric cancers due to its cytotoxic property.

• Botulinum neurotoxin(BoNT) briefly opens tumors vessels, allowing more effective destruction of cancer by radiotherapy and chemotherapy.

• Some other toxins undergoing on research are - alfa toxin from Stapylococcous aureus, - AC-toxins from Bordetella pertussis - shiga like toxins - cholera toxin

-BACTERIAL TOXIN CONJUGATED TO LIGAND

• Binding of toxins to cell-binding proteins .e.g Monoclonol antibodies or growth factors, cause regression in growth of cancer by targetting them into the specific sites on cancers.

• For example transferrin-Diphtheria toxin(DT), DT- epidermal growth factor(EGF) in brain tumor and metastatic carcinomas and IL4-PE against human gliboblastoma tumor

• Genetically modified and recombinant toxins e.g chimeric toxins

BACTERIA AS IMMUNOTHERAPEUTIC AGENTS

• Genetically engineered Attenuated Salmonella typhimurium expressing murine cytokines (IL-2) suppress the growth of tumor.

• Xenogenic DNA vaccine encoding tumor endothelial markers 8(TEM8) carried by attenuated S.typhimurium has been repoetd to generate TEM8-specific CD8 cytotoxic T-cell response after oral administration.

• C.novyi spores after systematic administration destroy adjacent cancer cell and trigger an inflammatory reaction by producing cytokinies such as IL-6, MIP-2, G-CSF, TIMP-1 and KC…

• CANCER VACCINE- A recombinant Listeria monocytogenes( facultative intracellular bacteria) vaccine strain expressing nucleoprotein (NP)from influenza strainA/PR8/34 has shown great therapeutic potential pre-clinically by regressing growth off microscopic tumors.

• Bacillus calmette-gurein (BCG-CWS) has been used as an effective adjuvent for immunotherapy.

PROBLEMS WITH BACTERIAL THERAPY

• Toxicity• Infections• Incomplete tumor lysis• DNA mutation

Conclusion• Live, attenuated bacteria as antitumor agents

and vectors for gene directed enzyme prodrug therapy have emerged as potential strategies.

• VNP20009 and TAPET-CD have been investigated successfully in phase 1 clinical trial.

• Chemeric toxins are also being investigated as future toxin-based anticancer therapies.

IMPORTANT CLINICAL TRIAL INVOLVING BACTERIAL INTERVENTION IN CANCER

INTERVENTION CLINICAL PRESENT STATUS DISEASE (NUMBER TRAIL PHASE CONDITIONCOMPOUND)

VNP20009 PHASE 1 COMPLETED ADVANCED OR METASTATIC SOLID TUMORS

TAPET-CD HEAD, NECK PHASE 1 COMPLETED ESOPHAGUS CANCER

Tf-CRM 107 PHASE 1 ONGOING BRAIN ENTRAL NERVOUS SYSTEM TUMOR

IL4-PE PHASE 1 ONGOING BRAIN ENTRAL NERVOUS SYSTEM TUMOR

MALIGNANT GILOMA, GLIBLASTOMA MULTIFORME IL3-PE PHASE 1 ONGOING ANAPLASTIC ASTROCYTOMA ANAPLASTIC

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