Cancer

Cancer

Overall, carcinogenesis involves

Full malignant transformation usually requires the cooperative action of multiple oncogenes and the loss of tumor suppressors. A single oncogene is rarely sufficient because cells possess multiple barriers—apoptosis, senescence, DNA-damage checkpoints—that must be overcome. Classic experiments demonstrated that Ras and Myc together bypass these barriers more effectively than either alone, illustrating the multi-hit nature of carcinogenesis.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cancer

One mechanism of chemotherapy resistance is

Defective apoptotic machinery, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cancer

MDR1 gene encodes

Over-expression of ATP-binding cassette transporters such as P-glycoprotein (encoded by MDR1) actively effluxes a wide range of hydrophobic drugs from the cytoplasm, reducing their intracellular concentration below the therapeutic threshold. This mechanism is a major cause of multidrug resistance in cancer chemotherapy. Inhibition of these pumps is therefore an active area of pharmacological research aimed at restoring drug sensitivity.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cancer

Multidrug resistance in cancer commonly involves overexpression of

Over-expression of ATP-binding cassette transporters such as P-glycoprotein (encoded by MDR1) actively effluxes a wide range of hydrophobic drugs from the cytoplasm, reducing their intracellular concentration below the therapeutic threshold. This mechanism is a major cause of multidrug resistance in cancer chemotherapy. Inhibition of these pumps is therefore an active area of pharmacological research aimed at restoring drug sensitivity.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cancer

Viral oncoproteins contribute to cancer mainly by

Neutralizing tumor suppressor proteins, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cancer

Loss of p53 cooperates with Ras by

The tumor-suppressor protein p53 is kept at low levels in unstressed cells by continuous MDM2-mediated ubiquitination and degradation. DNA damage or oncogenic stress leads to phosphorylation of p53 or induction of ARF, both of which block the p53–MDM2 interaction. Stabilized p53 then transcriptionally activates genes that induce cell-cycle arrest, DNA repair or apoptosis, thereby preventing propagation of damaged genomes.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cancer

Ras and Myc cooperate in cancer by

Full malignant transformation usually requires the cooperative action of multiple oncogenes and the loss of tumor suppressors. A single oncogene is rarely sufficient because cells possess multiple barriers—apoptosis, senescence, DNA-damage checkpoints—that must be overcome. Classic experiments demonstrated that Ras and Myc together bypass these barriers more effectively than either alone, illustrating the multi-hit nature of carcinogenesis.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cancer

Oncogene collaboration is required because

Full malignant transformation usually requires the cooperative action of multiple oncogenes and the loss of tumor suppressors. A single oncogene is rarely sufficient because cells possess multiple barriers—apoptosis, senescence, DNA-damage checkpoints—that must be overcome. Classic experiments demonstrated that Ras and Myc together bypass these barriers more effectively than either alone, illustrating the multi-hit nature of carcinogenesis.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cancer

Combined action of HPV E6 and E7 results in

High-risk human papillomavirus oncoproteins E6 and E7 cooperate to drive cervical carcinogenesis. E7 binds and inactivates Rb, releasing E2F and promoting cell-cycle progression. E6 recruits the ubiquitin ligase E6AP to target p53 for degradation, thereby disabling the apoptotic and checkpoint responses that would otherwise eliminate the proliferating infected cell. The combined action removes both major tumor-suppressor barriers.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cancer

HPV E6 oncoprotein promotes cancer by

High-risk human papillomavirus oncoproteins E6 and E7 cooperate to drive cervical carcinogenesis. E7 binds and inactivates Rb, releasing E2F and promoting cell-cycle progression. E6 recruits the ubiquitin ligase E6AP to target p53 for degradation, thereby disabling the apoptotic and checkpoint responses that would otherwise eliminate the proliferating infected cell. The combined action removes both major tumor-suppressor barriers.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cancer

HPV E7 oncoprotein promotes cancer by

High-risk human papillomavirus oncoproteins E6 and E7 cooperate to drive cervical carcinogenesis. E7 binds and inactivates Rb, releasing E2F and promoting cell-cycle progression. E6 recruits the ubiquitin ligase E6AP to target p53 for degradation, thereby disabling the apoptotic and checkpoint responses that would otherwise eliminate the proliferating infected cell. The combined action removes both major tumor-suppressor barriers.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cancer

Hyperphosphorylation of Rb leads to

Hypophosphorylated Rb binds and represses E2F transcription factors, preventing expression of genes required for S-phase entry. Mitogenic signaling activates cyclin-D–CDK4/6 and cyclin-E–CDK2 complexes that progressively phosphorylate Rb. Hyperphosphorylated Rb releases E2F, allowing S-phase progression. Loss of Rb function therefore removes a critical G1 checkpoint and contributes to uncontrolled proliferation. Careful

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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