Role of clostridium spores in cancer treatment AND their potential as drug delivery system

content Introduction History What we mean by Spores What we mean by Cancer Mechanism of clostridia anticancer effect Examples Types of spores used Cancer types treated

introduction Microorganisms are beneficial in Decomposition Food industry Medicine industry : antibiotics, vaccines Cancer treatment!!!

history Patients diagnosed with cancer reported unexpected cure of illness after gangrene infection caused by Clostridium perfringens. Later experiments investigated clostridia role in treating cancer

spores Spores are dormant structure of vegetative cell either bacterial or fungal. When they are bacterial in origin we call them endospores (simply spores)and when they are fungal in origin we call them exospores Endospores are formed when certain cells species that are gram positive bacteria like Bacillus and Clostridium spp. encounter environmental stresses like nutrient starvation Endospores have evolved many mechanisms to protect themselves from damage withstand harsh conditions and survive many years or even millions of years in that dormant state

Spore germination When shock occurs and favorable environment dominates the bacteria regenerate those steps called activation, germination and outgrowth

cancer It is a class of disease characterized by uncontrolled cell division, leading to abnormal growth. In tumor (cancerous) cells we lose the balance between signals enhancing and suppressing growth. The predisposing factor may be genetic, environmental , chemical exposure or harmful conditions like radiations which alter the genomic structure and processes There are different ways to treat cancer including radiotherapy, chemotherapy, and immunotherapy, surgery, hormone therapy and microorganisms

Cancer epidemiology In 2012 there were 14 million new cancer cases occurring worldwide, which contributed to around 8.2 million deaths. It is predicted that within the next 15 years the burden of cancer will increase to 23.6 million. Those statistics shows that cancer is still one of the leading causes of death worldwide so we need more effective and reachable treatments

Mechanism behind Clostridium anticancer effect Clostridium spp. as such has anticancer effect Clostridium spp. act as drug delivery system ↔ CDEPT (Clostridia directed enzyme prodrug therapy) In either ways our targeting mechanism is tumor hypoxia What is tumor hypoxia?

what is hypoxia

why are we interested in tumor hypoxia? 80% of cancerous tumors are solid tumors. Most solid tumors cores are poorly oxygenated tissue “hypoxic tumor”  necrotic core Tumor hypoxia reduce the effect of many anti-cancer drugs due to poor drug penetration related to poor vascularization , it also activates metastasis Patients diagnosed and surgically treated for primary tumors with severe hypoxia have lower survival As we see hypoxic tumor treatment is challenging and we need novel therapies

Novel strategies of hypoxic tumor therapy: DEPT (directed enzyme prodrug therapy): hypoxia activates spores that germinate to bacteria and activate a prodrug into drug DEPT includes : a-ADEPT (anti-body directed prodrug therapy): Fusion of PCE to a tumor specific antibody b- GDEPT (gene-Directed Enzyme prodrug therapy): delivery of gene encoding PCE using viral or non-viral vectors C-CDEPT (Clostridia directed enzyme prodrug therapy):

CDEPT CDEPT (Clostridia directed enzyme prodrug therapy): Anaerobic spore producing bacteria are modified genetically to produce PCE (prodrug converting enzyme). Then modified spores are produced to act as delivery system. Spores are injected. Once in necrotic tissue they will exclusively germinate and colonize to target tissue and start to produce PCE that converts the safe prodrug in the vicinity to very toxic drug with anticancer effect acting locally.

One of the noxia choices was prodrug-drug stragety Combination therapy with spores (Clostridia Directed Enzyme Prodrug Therapy CDEPT): The use of Clostridium strains was of great benefit, but later on it was discovered that combining it with noxia was more promising. One of the noxia choices was prodrug-drug stragety Ideal cancer therapy should be selective on tumor tissue this can be achieved targeting a safe prodrug that is converted into highly toxic drug only in tumor tissue using prodrug converting enzyme PCE  this procedure is called Directed Enzyme Prodrug Therapy (DEPT) (DEPT) can assure selective exposure of cells to effective dose .

Examples of effective combinations 1- novel PR-104 : alkylating agent ( DNA cross-linking agent), bioreductive dinitrobenzamide mustard 2-5-fluorocytosie (5-FC) converted to5- fluorouracil (5-FU) : CPE :Cytosine deaminase(codA) , 500-fold enhancement of cytotoxicity towards murine tumourcells, the used species was :C. beijerinckii NCIMB 8052

What type of spores can be used ? to satisfy that mechanism of action behind this theory 1-anaerobic 2- non-pathogenic spores must be used

The non-pathogenic species is the ones of importance in our delivery system like: 1- Proteolytic Species was of superior efficacy due to tumor destruction eg: a –Clostridium butyricum M-55 which showed significant oncolytic effects the strain was named Clostridium oncolyticum and later reclassified as Clostridium sporogenes M-55 b- Clostridium novyi-NT 2- Saccharolytic Clostridia such as Clostridium beijerinckii or Clostridium acetobutylicum which was effective but inferior to C. sporogenes

What type of cancer can be targeted ? Solid tumors as associated with hypoxia like refractory/relapsed acute leukemia

resistance This method is still under investigation and nothing about resistance is studied

conclusion 1- Clostridium genotype is altered to express the required PCE , all used genotypes carry plasmid responsible for antiabiotic resistance .   2-Clostridial-Directed Enzyme Prodrug Therapy CDEPT strain used to achieve substantial tumour suppression, and in some cases cure. 3-clostridia species seem destined to have a significant role to play in the future treatment of solid tumours.