173
Cancer is a complex disease that has roots from different causes put together. To
understand the biochemistry of cancer involves studying various factors starting
from the external environment to the intracellular network of biochemical pathways
involved. The disease has shown an increasing incidence with changing lifestyle,
food habits, and environmental threats including global warming. The battle against
cancer is weakening with the lack of number of potential drugs in clinical use. Many
of the drugs that are in clinical use either have varying degree of side effects or are
ineffective due to the surging problem of multidrug resistance property possessed
by the cancer. Natural products obtained from either plant or microbes have been
known to aid cancer treatment in the past decades.
Most of the anticancer drugs drive cancer cells into one of the modes of programmed cell death (PCD) namely apoptosis, autophagy, necroptosis, or a programmed mode of necrosis. It is necessary to understand the mechanism employed
by the anticancer drug in order to analyze the outcomes and possible side effects
caused. Apoptosis is a cascade of enzymatic events which leads to programmed cell
suicide. Apoptosis is also involved in normal development and aging, and it maintains cell population in tissues by selectively removing damaged or stressed cells.
This mode of cell death is also employed as a defense mechanism in the event of cell
damage by disease or other toxic agents (Norbury and Hickson 2001). Cancer cells
equip themselves with highly complex mechanism to avoid PCD and thus evade
apoptosis by down-regulating or up-regulating expression of proteins required for
the cancer-cell sustainment and proliferation. Induction of apoptosis can be initiated
by a range of stimuli or combination of physiological and pathological conditions.
Most of the anticancer drug treatment leads to DNA damage, based on the type of
cell being treated; apoptosis; or other forms of cell death. Apoptosis involves a
group of enzymes called caspases that carry out the cell death process. Apoptosis
leads to series of morphological changes, during the initial phase, and the caspasedependent mechanism puts the last nail on the coffin of the cancer cell.
Autophagy is another well-defined process that employs a self-degradative mechanism that plays important role in the event of development and nutrient stress. Autophagy
also helps in the eviction of misfolded or damaged proteins, damaged organelles, and
removal of intracellular pathogens. Autophagy is considered a cell- survival mechanism,
but it is also linked to nonapoptotic cell death. There are around 32 different autophagyrelated genes identified through genetic screening in yeast, and most of these genes are
conserved in plants and mammals (Nakatogawa et al. 2009). Necrosis, which was initially believed by researchers to be a passive form of cell death, was later researched and
identified to be programmed mechanism of cell death (Degterev et al. 2005). Some of
the cellular protein molecules like TNFα, FasL, and TRAIL are known to be involved in
induction of apoptosis and are also linked to necrosis.
7.2
Anticancer Drugs from Marine Microorganisms
Drug discovery for cancer has been vastly based on hunting potential molecules
from terrestrial organisms, from microbes to plants. Many of these compounds and
their derived forms from terrestrial origin are in clinical use or undergoing clinical
7 Anti Cancer Agents from Microbes
Cancer is a complex disease that has roots from different causes put together. To
understand the biochemistry of cancer involves studying various factors starting
from the external environment to the intracellular network of biochemical pathways
involved. The disease has shown an increasing incidence with changing lifestyle,
food habits, and environmental threats including global warming. The battle against
cancer is weakening with the lack of number of potential drugs in clinical use. Many
of the drugs that are in clinical use either have varying degree of side effects or are
ineffective due to the surging problem of multidrug resistance property possessed
by the cancer. Natural products obtained from either plant or microbes have been
known to aid cancer treatment in the past decades.
Most of the anticancer drugs drive cancer cells into one of the modes of programmed cell death (PCD) namely apoptosis, autophagy, necroptosis, or a programmed mode of necrosis. It is necessary to understand the mechanism employed
by the anticancer drug in order to analyze the outcomes and possible side effects
caused. Apoptosis is a cascade of enzymatic events which leads to programmed cell
suicide. Apoptosis is also involved in normal development and aging, and it maintains cell population in tissues by selectively removing damaged or stressed cells.
This mode of cell death is also employed as a defense mechanism in the event of cell
damage by disease or other toxic agents (Norbury and Hickson 2001). Cancer cells
equip themselves with highly complex mechanism to avoid PCD and thus evade
apoptosis by down-regulating or up-regulating expression of proteins required for
the cancer-cell sustainment and proliferation. Induction of apoptosis can be initiated
by a range of stimuli or combination of physiological and pathological conditions.
Most of the anticancer drug treatment leads to DNA damage, based on the type of
cell being treated; apoptosis; or other forms of cell death. Apoptosis involves a
group of enzymes called caspases that carry out the cell death process. Apoptosis
leads to series of morphological changes, during the initial phase, and the caspasedependent mechanism puts the last nail on the coffin of the cancer cell.
Autophagy is another well-defined process that employs a self-degradative mechanism that plays important role in the event of development and nutrient stress. Autophagy
also helps in the eviction of misfolded or damaged proteins, damaged organelles, and
removal of intracellular pathogens. Autophagy is considered a cell- survival mechanism,
but it is also linked to nonapoptotic cell death. There are around 32 different autophagyrelated genes identified through genetic screening in yeast, and most of these genes are
conserved in plants and mammals (Nakatogawa et al. 2009). Necrosis, which was initially believed by researchers to be a passive form of cell death, was later researched and
identified to be programmed mechanism of cell death (Degterev et al. 2005). Some of
the cellular protein molecules like TNFα, FasL, and TRAIL are known to be involved in
induction of apoptosis and are also linked to necrosis.
7.2
Anticancer Drugs from Marine Microorganisms
Drug discovery for cancer has been vastly based on hunting potential molecules
from terrestrial organisms, from microbes to plants. Many of these compounds and
their derived forms from terrestrial origin are in clinical use or undergoing clinical
7 Anti Cancer Agents from Microbes