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Negative growth control of HeLa cells by connexin genes: connexin species specificity
M Mesnil1, V Krutovskikh, C Piccoli
1International Agency for Research on Cancer, Lyon, France.
Abstract:
In order to examine whether different connexin gene species exert different degrees of tumor-suppressing activity, we characterized growth characteristics of a gap junction-deficient human cancer cell line, HeLa cells, before and after transfection with cDNA for three different connexins, connexin (cx) 26, cx 40, and cx 43. All transfected cell lines (3 clones transfected with the cx 26 gene, 2 clones with cx 40, and 1 with cx 43) showed establishment of gap junctional intercellular communication (GJIC). Two of the cx 26-transfected clones showed significantly slower growth compared with the parental HeLa cells. When transfectants were grown in soft agar, the three cx 26-transfected clones grew much less than the other transfectants and parent HeLa cells. When injected into nude mice, the two cx 26 clones which exhibited the highest amount of cx 26 transcript induced almost no tumors, whereas other transfectants, including the cx 26 clone which exhibited the lowest amount of cx 26 transcript, were tumorigenic. Among transfectants of various connexin genes, there was no good inverse correlation between their GJIC and tumorigenicity. GJIC levels were significantly higher in tumors induced in nude mice by clone cx 26 A and E transfectants. These results suggest that all of the connexin genes examined could induce recovery of GJIC of HeLa cells, but only the cx 26 gene exerts strong negative growth control on HeLa cells; thus, this connexin gene may have different functions from other connexin genes.
Insights
Connexin 26 (cx 26) gene transfection significantly suppressed tumor growth and tumorigenicity in HeLa cells, unlike connexin 40 and connexin 43. This suggests cx 26 has unique tumor-suppressing functions distinct from other connexins.
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Biology
Background:
- Gap junctional intercellular communication (GJIC) is crucial for cell regulation.
- Dysregulation of GJIC is implicated in cancer development.
- Different connexin (cx) gene species may have varying roles in tumor suppression.
Purpose of the Study:
- To investigate the tumor-suppressing activity of different connexin gene species.
- To compare the effects of connexin 26, 40, and 43 on HeLa cell growth and tumorigenicity.
Main Methods:
- Transfection of a gap junction-deficient human cancer cell line (HeLa) with cDNA for cx 26, cx 40, and cx 43.
- Characterization of growth characteristics, soft agar colony formation, and tumor formation in nude mice.
- Measurement of GJIC levels and connexin transcript levels.
Main Results:
- All transfected cell lines established GJIC.
- Connexin 26 (cx 26) transfected clones showed significantly slower growth and reduced soft agar colony formation compared to controls.
- Two cx 26 clones exhibited minimal tumor formation in nude mice, while other transfectants remained tumorigenic.
- No clear inverse correlation between GJIC levels and tumorigenicity was observed across different connexin types.
Conclusions:
- While all tested connexin genes restored GJIC in HeLa cells, only cx 26 demonstrated significant tumor-suppressing activity.
- Connexin 26 appears to exert a distinct negative growth control mechanism on cancer cells.
- These findings suggest connexin 26 may possess unique tumor-suppressing functions compared to other connexin genes.