This one made me think..

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This one made me think..

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indidoc1
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03/04/07 - 06:16 AM

Many drugs that are used to treat cancer cause death
of tumor cells by apoptosis. Mutational inactivation of
which of the following genes can render tumor cells resist-
ant to the effects of such chemotherapeutic drugs?

(A) bcl-2
(B) p53
(C) NF-k B
(D) P450
(E) Granzyme B

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babydoc4usmle
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03/04/07 - 03:12 PM

read uncle G - BCL-2=antiapoptotic gean ---> mutation of this gean renders cell living "forever" = no apoptosis occures
this is what i remember at least

new_n_lost
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03/04/07 - 06:32 PM

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Ancylostoma
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03/04/07 - 07:12 PM

even kaplan of mentions it ...they call it the "fountain of life gene" - bcl2

I never forget it now because of that line

indidoc1
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03/04/07 - 11:59 PM

I knew this ws a goooood Q nod

even i fell fr it..

Now guys.. consider this..

bcl-2 is the gene that prevents apoptosis (the fountain of youth).. So what happens if thats mutated???
As our G man would say "DAAA!!" grin

The cancer cells ll be rushing at full speed into apoptosis. And they would not be resistant to anti-cancer drugs.. In fact, maybe we won't need anti cancer drugs then wink

on the other hand.. p53 halts up the cell cycle n stimulates apoptosis.. So.. its mutation ll remove the inducer of apoptosis n increase cancer cell survival..

So, the answer's B

Now u know why i said "This one made me think" wink

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indidoc1
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03/05/07 - 12:00 AM

n here's the official explanation to go along wth what i wrote above..

(B) On DNA damage induced by chemotherapeutic
drugs (or other agents), normal p53 genes trigger the cells
to undergo apoptosis. When p53 is inactivated, this path-
way of cell death can be blocked, rendering the chemother-
apy less effective, bcl-2 and NF-KB favor cell survival.
Cytochrome P450 does not affect apoptosis. Granzyme B
is found in cytotoxic T cells and not tumor cells. It triggers
apoptosis.

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babydoc4usmle
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03/05/07 - 06:42 AM

The protein Bcl-2 is an anti-apoptotic protein that resides in the OMM and the membrane of the endoplasmic reticulum. Over expression of Bcl-2 is known to block cytochrome c release, possibly through the inhibition of Bax and Bak...

Role in disease

The Bcl-2 gene has been implicated in a number of cancers, including melanoma, breast, prostate and lung carcinomas. It is also thought to be involved in resistance to conventional cancer treatment. This supports a role for decreased apoptosis in the pathogenesis of cancer...

i would revise this kind of questions. nod

babydoc4usmle
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03/05/07 - 07:00 AM

BTW, mutation is not nesessary loss of gene, it can be over-production of coded protein/product and it was not specified in the question

indidoc1
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03/05/07 - 08:04 AM

indidoc1 wrote:
Mutational inactivation of
which of the following genes can render......

n u r right... we do need to revise such Qs.. Somehow.. i always manage to get confused in these shaking head

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indidoc1
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03/05/07 - 08:05 AM

#10

n thanks fr the gr8 info on bcl-2 nod

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babydoc4usmle
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03/05/07 - 08:18 AM

#11

oops, missed that part grin

unique1
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03/06/07 - 08:19 AM

#12

Good Q . Made me think too . grin

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