The Story of Bcl-2 The Story of Bcl-2 Linking cell apoptosis to tumor Linking cell apoptosis to tumor

metastasismetastasis

Crystal structure of Bcl-2 complex By Yaming Wang

HistoryHistory

Bcl-2 was first isolated Bcl-2 was first isolated in in B Cell Lymphoma B Cell Lymphoma cellscells Caused by malignant B Caused by malignant B

lymphocyteslymphocytes Contributes about 85% of Contributes about 85% of

known types of known types of lymphoma in USlymphoma in US Immunofluorescence stain of

B cells in the spleen(green= Bcl-2)

History continuedHistory continued

The mutation of Bcl-2 was due to chromosome The mutation of Bcl-2 was due to chromosome translocationtranslocation Very similar to the story of Cyclin D as an oncogeneVery similar to the story of Cyclin D as an oncogene

Mistake happens during BCR (VDJ) Mistake happens during BCR (VDJ) rearrangementrearrangement

Bcl-2 gene (from chromosome 14) is Bcl-2 gene (from chromosome 14) is placed next to Ig heavy chain locus on placed next to Ig heavy chain locus on chromosome 18chromosome 18

This leads to the overexpression of Bcl-This leads to the overexpression of Bcl-2 in B cells 2 in B cells

But what is the mechanism But what is the mechanism that makes Bcl-2 a killer? that makes Bcl-2 a killer?

Bcl family proteins govern Bcl family proteins govern programmed cell death (apoptosis)programmed cell death (apoptosis)

Bcl-2 protein BiochemistryBcl-2 protein Biochemistry

Bcl-2 is a small protein (~29KD)Bcl-2 is a small protein (~29KD) Bcl family proteins play crucial role in cell Bcl family proteins play crucial role in cell

apoptosis apoptosis Divided into pro-survival and pro-apoptosis and Divided into pro-survival and pro-apoptosis and

usually balance each other out in healthy cellsusually balance each other out in healthy cells Bcl-2 is a pro-survival protein and it protects cell Bcl-2 is a pro-survival protein and it protects cell

from a wide range of cytotoxic insults, including from a wide range of cytotoxic insults, including cytokine deprivation, UV and cytokine deprivation, UV and -irradiation-irradiation

Highly conserved BH domainsHighly conserved BH domains Bcl family proteins share Bcl family proteins share

highly conserved regions highly conserved regions called called Bcl homology Bcl homology (BH) domain(BH) domain

Structurally, divided into 3 Structurally, divided into 3 families families

BH3-only family proteins BH3-only family proteins bind to pro-survival family bind to pro-survival family proteins at the groove proteins at the groove formed by BH1, BH2, and formed by BH1, BH2, and BH3 domainsBH3 domains Binding triggers the switch Binding triggers the switch

of apoptosis signaling of apoptosis signaling

Proposed MechanismProposed Mechanism- - protection of mitochondrial integrity by Bcl-2protection of mitochondrial integrity by Bcl-2

Bcl proteins are highly regulatedBcl proteins are highly regulated

In response to different signal (ie. Death, In response to different signal (ie. Death, or proliferation), Bcl family proteins are up/ or proliferation), Bcl family proteins are up/ down regulated.down regulated.

Example: Regulation of T lymphocytesExample: Regulation of T lymphocytes

Yaming Wang, unpublished data, Microbiology and Immunology, 2006

In response to the immunosuppression signal, Bcl-XL level is down regulated.

What happen if Bcl-2 is What happen if Bcl-2 is over expressed or knocked over expressed or knocked

out in mice?out in mice?

What happen if Bcl-2 is over expressed or knocked What happen if Bcl-2 is over expressed or knocked out in mice?out in mice?

Bcl-2 over expressing mice:Bcl-2 over expressing mice:B cell lymphomas are frequently found B cell lymphomas are frequently found

Bcl-2 knock out mice:Bcl-2 knock out mice:Viable but show growth retardationViable but show growth retardationSevere polycystic kidney diseaseSevere polycystic kidney diseaseMassive apoptotic involution in thymus and Massive apoptotic involution in thymus and

spleenspleen

Linking anti-apoptosis to tumor Linking anti-apoptosis to tumor metastasismetastasis

Bcl-2 is also over expressed in many Bcl-2 is also over expressed in many cancers including cancers including lung, colorectal, lung, colorectal, prostate, and breast, prostate, and breast, as well as inas well as in leukemia leukemia and otherand other lymphomas lymphomas

Several changes are Several changes are requiredrequired

Eg. they have to lose their Eg. they have to lose their dependence to dependence to local local growth factorsgrowth factors, ability to , ability to survive without survive without integrin integrin signalssignals

All these changes normally All these changes normally lead to cell apoptosislead to cell apoptosis

Overcome by Overcome by overexpressing pro-overexpressing pro-survival Bcl family proteinssurvival Bcl family proteins

Alberts et al. Fig. 24-16

Recent studies have shown that prolonged Recent studies have shown that prolonged cell survival induced by the overexpression cell survival induced by the overexpression of Bcl-2 protein promotes the metastasis of of Bcl-2 protein promotes the metastasis of many cancer cells such as melanoma cells many cancer cells such as melanoma cells and mammary epithelial cells.and mammary epithelial cells.

Therefore, it maks Bcl protein a very good Therefore, it maks Bcl protein a very good target for cancer therapy.target for cancer therapy.

ReferencesReferences The lymphoma information network. http://www.LymphomaInfo.net/The lymphoma information network. http://www.LymphomaInfo.net/ Veis D.J., Sorenson C.M., Bcl-2-deficient mice demostrate fulminant Veis D.J., Sorenson C.M., Bcl-2-deficient mice demostrate fulminant

lymphod apoptosis, polycystic kidneys, and hypopigmented hiar, lymphod apoptosis, polycystic kidneys, and hypopigmented hiar, CellCell, 75, 2, 1993 229-240, 75, 2, 1993 229-240

Pinkas J., Martin S.S., Bcl-2-mediated cell survival promotes Pinkas J., Martin S.S., Bcl-2-mediated cell survival promotes metastasis of EpH4 BMEKDD mammary epithelial cells, metastasis of EpH4 BMEKDD mammary epithelial cells, Mol Cancer Mol Cancer ResRes; 2(10), 2004; 2(10), 2004

Anderson M.H., Svane I.M., Immunogenicity of Bcl-2 in patients with Anderson M.H., Svane I.M., Immunogenicity of Bcl-2 in patients with cancer, cancer, BloodBlood, 105, 2, 2005, 105, 2, 2005

Takaoka A., Adachi M., Anti-cell death activity protomtes pulmonary Takaoka A., Adachi M., Anti-cell death activity protomtes pulmonary metastasis of melanoma cells, metastasis of melanoma cells, OncogenOncogen, 14, 1997, 2971-2977, 14, 1997, 2971-2977

Cory S., Adams J.M., The Bcl-2 family: regulators of the cellular life-Cory S., Adams J.M., The Bcl-2 family: regulators of the cellular life-or-death switch, or-death switch, NatureNature, 2, 2002, 647-656, 2, 2002, 647-656

Thank you very much!Thank you very much!Have a good Spring Break!Have a good Spring Break!

Cancer therapies targeting Bcl-2 Cancer therapies targeting Bcl-2 over expressionover expression

Some drugs that inhibit Bcl-2 by BH3 mimeticsSome drugs that inhibit Bcl-2 by BH3 mimetics Antisense oligonucleotide (inhibit mRNA translation)Antisense oligonucleotide (inhibit mRNA translation) More interestingly, shown that Bcl-2 over expression is in More interestingly, shown that Bcl-2 over expression is in

fact immunogenic. (meaning we can generate immunity fact immunogenic. (meaning we can generate immunity against cells in which Bcl-2 is over expressed. ie. cancer against cells in which Bcl-2 is over expressed. ie. cancer cells.)cells.)

This gives us a way to target cancer cells using the This gives us a way to target cancer cells using the weapons in our body (immune system) without harming weapons in our body (immune system) without harming healthy cells in cancer therapy. healthy cells in cancer therapy.